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Question 0

What is the value of histology?

Answer 0

Final proof of a disease- most doctors won’t decide on treatment without a histopathological diagnosis. Defines the extent of a disease

Question 1

Why do shrinkage artefacts form?

Answer 1

In the dehydration process the dehydrating agents (ethyl alcohol) cause artifactual tears or splits to form along lines of weakness in the tissue - this unnatural space, shrinkage artefact, is visible under the microscope

Question 2

How does formaldehyde and glutaraldehyde fix a biopsy?

Answer 2

Preserves cellular proteins by cross linking macromolecules. Aldehydes form covalent bonds with the amine groups on the proteins and thus cross link adjacent proteins, arresting biological activity and making cells more susceptible to staining

Question 3

List the 11 steps of tissue processing

Answer 3

Biopsy, fixation, dehydrating, clearing, embedding, sectioning, rehydrating, staining, dehydrating, mounting, microscopy

Question 4

What is meant by the process of biopsy?

Answer 4

The removal of a piece of tissue from an organ or part of the body for microscopic examination

Question 5

Name 2 fixatives

Answer 5

Formaldehyde and glutaraldehyde

Question 6

Name a dehydrating agent

Answer 6

Ethyl alcohol

Question 7

Name 2 clearing agents

Answer 7

Xylene or toluene

Question 8

How is a sample embedded in wax?

Answer 8

Paraffin wax at 56 degrees Celsius

Question 9

Define a tissue

Answer 9

Collection of cells working together to perform a particular function

Question 10

What does haematoxylin stain?

Answer 10

Acids blue

Nucleoli/ chromatin

Question 11

What does eosin stain?

Answer 11

Bases pink

Cytoplasmic proteins
Extra cellular substances/ fibres

Question 12

What does periodic acid schiff (PAS) stain?

Answer 12

Stains carbohydrates and glycoproteins magenta

Mucus secreting goblet cells
Basement membrane

Question 13

What is used to mount a sample?

Answer 13

Dpx drying (xylene based medium)

Question 14

What is gram staining used for?

Answer 14

To stain bacteria

Question 15

What is the process of gram staining?

Answer 15

Add crystal violet complex (+) which binds to negatively charged structures 
Add iodine (-) which binds to the crystal violet and stains it purple
Methanol is added to extract the complex from within the cell 

Gram positive- has a thick peptidoglycan wall and so complex is not extracted by methanol and the structure stains purple still
Gram negative- has little or no peptidoglycan wall and so complex is extracted by methanol and the structure stains red

Question 16

Why can’t mycobacterium be stained by gram staining?

Answer 16

Have no peptidoglycan cell wall

Question 17

What bacteria are mycobacterium?

Answer 17

Tb and leprosy

Question 18

What staining technique can be used for mycobacterium and what stain does it use?

Answer 18

Acid fast technique using a Z-N stain

Question 19

What bacteria are gram positive?

Answer 19

Cocci and clostridium

Question 20

What bacteria are gram negative?

Answer 20

Neisseria and everything else except mycobacterium and chlamydia

Question 21

What is the value of histological staining?

Answer 21

To enable the visibility of components of a cell through a microscope

Question 22

What is phase contrast microscopy?

Answer 22

Uses the interference effects of two combining light waves

Question 23

What are the advantages of using phase contrast microscopy?

Answer 23

It enhances the images of unstained cells

Question 24

What is dark field microscopy?

Answer 24

It excludes unscattered beams (light or electron) from the image Used to detect malaria or syphilis

Question 25

What are the advantages of using dark field microscopy?

Answer 25

Can look at live and unstained samples

Question 26

What is confocal light microscopy?

Answer 26

Tissue is labelled with one or more fluorescent probes

Question 27

What are the advantages of confocal light microscopy?

Answer 27

Eliminates the out of focus flare 3d from a series of 2d images Imaging of living specimens Allows thick samples to be used

Question 28

What is fluorescent microscopy?

Answer 28

Targets molecule of interest with a fluorescently labelled monochromal antibody

Question 29

What are the advantages of fluorescent microscopy?

Answer 29

Uses multiple fluorescent stains on one specimen to identify different parts of a sample

Question 30

What is histology?

Answer 30

Study of structures of tissues using specialised staining techniques combined with light or electron microscopy

Question 31

Define the limit of resolution

Answer 31

The minimum distance at which two objects can be distinguished Lor is directly proportional to the wavelength

Question 32

What is the difference between light and electron microscopy?

Answer 32

Light uses visible light, whereas electron uses electrons Light- wavelength = 0.4-0.7 micrometers and Lor= about 0.2 micrometers Electron- wavelength depends on accelerating voltage used (e.g. At 100000V wavelength= 0.004 nm Tem- Lor= 2nm Sem- Lor= 10nm

Question 33

Explain why electron microscopes are capable of a finer resolution than light microscopes

Answer 33

Visible light wavelength= 0.4-0.7 micrometers; Lor= 0.2 micrometers Electron at 100000V acceleration wavelength= 0.004nm; Lor= 0.002nm Electron microscopes have a smaller wavelength and thus a smaller lor than light microscopes

Question 34

Structure and function of cell membrane (bilipid)

Answer 34

Phospholipid bilayer with intrinsic proteins (carriers) and extrinsic proteins (with glycoprotein receptors) = fluid mosaic model Allows free transport of lipid soluble substances across membrane; proteins facilitate movement of water soluble substances across

Question 35

Structure and function of plasma membrane (plasmalemma)

Answer 35

Surrounds cells Selective permeability, signal transduction, intracellular adhesion and recognition, transport into and out (endo and exo cytosis)

Question 36

Structure and function of glycocalyx

Answer 36

Cell coat made up of oligosaccharide and polysaccharide side chains on outside of plasma membrane Side chains give the cells specificity

Question 37

Structure and function of nucleus

Answer 37

Nucleus, nuclear envelope, nucleolus, mostly consists of chromatin (unstructured form of cells DNA that will organise to form chromosomes during mitosis) -heterochromatin and euchromatin Stores cells DNA and coordinates cells activities (metabolism, growth, protein synthesis and mitosis)

Question 38

Structure and function of nuclear envelope

Answer 38

Double layered membrane that separates the contents of the nucleus from the cellular cytoplasm. Envelopes has lots of holes called nuclear pores that allow specific types and sizes of molecules to pass through. Also has an attached network of tubules - ER

Question 39

Structure and function of nucleolus

Answer 39

Found within the nucleus | Synthesises protein producing macro molecular structures called ribosomes

Question 40

Structure and function of ribosomes

Answer 40

Found free in cytoplasm or attached to ER Humans 80S (60 and 40) and Bacteria 70S (50 and 30) Two subunits small and large Complex of rRNA and many proteins that act as a mini protein factory Synthesised by the nucleolus Sites of translation- protein synthesis

Question 41

Structure and function of RER

Answer 41

Ribosomes attached (ribosome only binds to the ER once it begins to synthesise a protein destined for the secretory pathway MGD- i.e. to be secreted, vesicles, or for the membrane); membrane of RER is continuous with outer layer of nuclear envelope Produces lysosomal enzymes with a mannose 6 phosphate marker added in the cis Golgi network Secreted proteins- constitutively (collagen) or regulated (insulin) N linked glycosylation

Question 42

Structure and function of SER

Answer 42

Not associated with ribosomes; cisternae not as flattened as RER; less extensive; scattered around cytoplasm Liver and mammary gland- lipid synthesis and intracellular transport Ovaries, testes, adrenal glands- steroidogenesis

Question 43

Structure and function of Golgi apparatus

Answer 43

Golgi consists of stacks if cisternae Vesicles bud off from the RER and fuse with cis face of Golgi Golgi bodies have a polarity such that proteins migrate from the convex to the concave (cis to trans) face of the stack Functions to modify, sort, concentrate and package proteins synthesised in RER O linked glycosylation Vesicles containing different protein leave the maturing, trans face of the golgi and are destined for lysosome assembly, membrane or secretion Secretory vesicles often condense (secretory granules) and release their contents at the cell surface by exocytosis

Question 44

Structure and function of lysosomes

Answer 44

Contain acid hydrolases at pH 5; Lysosomal membrane proteins are highly glycosylated for protection from these enzymes; no genome of their own; dense, spherical or oval (primary) Primary lysosomes fuse with membrane bounded vesicles (phagosomes or endosomes) with autophagosomes (defunct organelles encircles by ER) or with excess secretory product to form secondary lysosomes (digestive vacuoles= phagolysosome) Degrade the contents of vacuoles Lysosomes that have digested their contents but contain indigestible remnants are called residual bodies

Question 45

What are residual bodies?

Answer 45

Lysosomes which have degraded their content but still contain indigestible material

Question 46

Structure and function of peroxisomes

Answer 46

Major site of oxygen utilisation and hydrogen peroxide production (catalase uses the hydrogen peroxide (ie. with ROS- HP is oxidised into water and oxygen AND in alcohol metab- alcohol --> acetaldehyde)) Roughly spherical containing granular matrix, bound by single membrane; Self replicating but no genome of their own so proteins must be imported; present in all cells (ESP. Kidney tubules and liver parenchymal cells) which detoxify toxic molecules that enter the blood stream Detoxification reactions

Question 47

Structure and function of mitochondria

Answer 47

Double membrane- inner membrane folded to form cristae (usually lamellar but are tubular in cells engaged in steroid synthesis- ovaries, testes, adrenals) Matrix contains enzymes of krebs and fatty acid cycles, DNA, RNA, ribosomes and calcium granules (ca signals to regulate mitochondrial function and acts to stimulate ATP synthesis) Mitochondria can divide and have their own genetic info; dna, ribosomes and division is similar to bacteria; maternal lineage inheritance Found in large numbers in liver and skeletal muscles; not found in rbc's or terminal keratinocytes Generation of energy rich ATP molecules by oxidative phosphorylation (main substrates are glucose and fatty acids)

Question 48

Structure and function of cytoskeleton

Answer 48

Micro filaments, intermediate filaments and micro tubules Produced by cells; responsible for maintaining/ changing cell shape Structural support for plasma membrane and cell organelles Means of movement for organelles, plasma membrane and other cytosol constituents Locomotor mechanisms for ameboid movements (e.g. Lymphocytes) and for cilia and flagella Contractability in cells of specialised tissues (e.g. Muscle) SMLC (structure, movement, locomotor, contractability)

Question 49

Structure and function of micro filaments

Answer 49

``` 5nm diameter Two strings of actin twisted together Associated with ATP (contractile) Can assemble or dissociate (dynamic) E.g. Core of actin filaments allows intestinal micro villi to maintain their shape ```

Question 50

Structure and function of intermediate filaments

Answer 50

SUPPORT Not dynamic 10-12 nm in diameter Common in nerve and neurological cells Also common in epithelial cells that are made of cytokeratin Form tough supporting mesh work in the cytoplasm and are anchored to plasma membrane at strong intracellular junctions (desmosomes)

Question 51

Structure and function of Microtubules

Answer 51

MOVEMENT OF STRUCTURES WITHIN CELLS 13 alpha and beta sub units polymerise to form the wall of the hollow micro tubules - Originate from the centrosome/centriole (tubular units are added or subtracted) Found at sites where structures in cells are moved (e.g. Elongated cellular processes such as nerve fibres, mitotic spindle and cores of cilia (9+2) and flagella) Attachment proteins (dyenin and kinesin) can attach to organelles and move them along the micro tubules (classic e.g. movement of chromosomes along the mitotic spindle)

Question 52

What are heterochromatin and euchromatin?

Answer 52

The DNA in the nucleus exist in two forms that reflect the level of activity of a cell. Heterochromatin appears as small, darkly staining, irregular particles scattered throughout the nucleus or accumulated adjacent to the nuclear envelope. Euchromatin is prevalent in cells that are active in the transcription of many of their genes while heterochromatin is most abundant in cells that are less active or not active. Heterochromatin: darker, more sparsely distributed, present in cells that are inactive in the transcription of genes Euchromatin: lighter, more evenly distributed, present in cells that are active in the transcription of their genes

Question 53

Define epithelia

Answer 53

Sheets of contiguous cells that cover the external surface of the body and line internal surfaces, with varying embryonic origin

Question 54

Name the three layers of the trilaminar embryonic disc

Answer 54

Ectoderm Mesoderm Endoderm

Question 55

What epithelia cells are derived from the ectoderm?

Answer 55

Epidermis of the skin Corneal epithelium of the eye (EXTERIOR SURFACES)

Question 56

What epithelia cells are derived from the mesoderm?

Answer 56

Epithelia of the urogenital tract (exception) Blood and lymph vessel lining- endothelium Pericardial and pleural sac lining Peritoneal lining (INTERIOR SPACES NOT OPENING TO THE EXTERIOR)

Question 57

What epithelia cells are derived from the endoderm?

Answer 57

Epithelia of respiratory tract Epithelia of GI tract Epithelia of liver Epithelia of many glands- thyroid, salivary, thymus (INTERIOR SPACES OPENING TO THE EXTERIOR)

Question 58

Where is basement membrane located?

Answer 58

Located between the epithelia cells and the lamina propria (subtending connective tissue)

Question 59

What is the basement membrane?

Answer 59

Thin, flexible, acellular layer beneath the epithelial cells

Question 60

What is the structure of the basement membrane?

Answer 60

It consists of a basal lamina, which is laid down by epithelial cells and therefore lies closest to them. Its thickness can be increased by a variably thick layer of reticular fibrils (type III collagen) elaborated by lamina propria (subtending connective tissue)

Question 61

What is the function of the basement membrane?

Answer 61

Serves as a strong flexible layer to which epithelial cells adhere Serves as a molecular and cellular filter The degree to which malignant cells penetrate the basement membrane is highly relevant to prognosis

Question 62

What is the clinical relevance of the basement membrane?

Answer 62

If malignant cells penetrate the basement membrane = poorer prognosis

Question 63

How are epithelia cells classified?

Answer 63

Simple- single layer thick Compound/ stratified- more than one layer thick Squamous, cuboidal, columnar, pseudostratified, transitional

Question 64

What are the functions of simple squamous epithelia and where are they found?

Answer 64

Lubrication (pericardium, pleura) Gas exchange (pulmonary alveoli) Active transport (via pinocytosis in endo/mesothelium) Barrier (bowmans capsule) ``` Glomerulus Bowmans capsule Alveoli Mesothelium (pericardium, peritoneum, pleural Endothelium (blood vessel lining) ```

Question 65

What are endothelium and mesothelium

Answer 65

Endothelium- lining of blood vessels | Mesothelium- lining of body cavities (pericardium, pleura, peritoneum)

Question 66

How does the structure of simple squamous epithelia help its function?

Answer 66

Thin so minimises diffusion distances | Flexibility

Question 67

What are the functions of simple cuboidal epithelia and where are they found?

Answer 67

Hormonal Mobilisation & Secretion & Storage (thyroid) Absorption- exocrine glands and kidney tubules Secretion Kidney tubules Thyroid gland Small ducts of exocrine glands m

Question 68

How does the structure of simple cuboidal epithelia help its function?

Answer 68

Absorption and secretion roles

Question 69

What are the functions of simple columnar epithelia and where are they found?

Answer 69

Absorption Lubrication Secretion ``` Gall bladder Large ducts of exocrine glands Oviducts Small intestine Stomach Salivary gland (parotid) ```

Question 70

How does the structure of simple columnar epithelia help its function?

Answer 70

MICRO VILLI AND CILIA Absorbing function Have micro villi which increase their surface area (small intestine) Have cilia to help move substances along it's surface (Fallopian tubes) Also contain interspersed glands

Question 71

What are the functions of pseudostratified epithelia and where are they found?

Answer 71

``` Secretion Conduit Absorption Mucus secretion Particle trapping S ``` Bronchus Lungs Trachea Epididymis

Question 72

How does the structure of pseudostratified epithelia help its function?

Answer 72

CILIA AND STEREOCILIA Appear to be more that one cell thick, but all cells do touch the basement membrane Cells are interspersed with mucus secreting goblet cells Cells generally have cilia which facilitate movement of other substances across surface (trachea) Cells can also have stereocilia assisting with reabsorption (epididymis)

Question 73

What are the functions of non keratinised stratified squamous epithelia and where are they found?

Answer 73

Abrasion Water loss prevention Vagina Oesophagus Mouth (epiglottis- also have pseudostratified)

Question 74

How does the structure of non keratinised stratified squamous epithelia help its function

Answer 74

Many layers means that water loss is prevented and that abrasion can be prevented

Question 75

What are the functions of keratinised stratified squamous epithelia and where are they found?

Answer 75

Protection Protection against UV Protection against microbes Prevention of water loss Skin Oral cavity

Question 76

How does the structure of keratinised stratified squamous epithelia help its function?

Answer 76

Keratin layer helps with prevention of water loss and protection (link to SKIN- epidermis:HGPB (keratinocytes)/ dermis/ hypodermis) Many layers is helpful with protection

Question 77

What are the functions of stratified cuboidal epithelia and where are they found?

Answer 77

Secretion Lining of sweat glands Glandular ducts

Question 78

How does the structure of stratified cuboidal epithelia help its function?

Answer 78

Cuboidal shape- secretion and absorption | ???

Question 79

What are the functions of stratified columnar epithelia and where are they found?

Answer 79

Secretion Pharynx Epiglottis Large exocrine glands Male urethra

Question 80

How does the structure of stratified columnar epithelia help its function?

Answer 80

Columnar shape- absorption and secretion | ???

Question 81

What are the functions of transitional epithelia and where are they found?

Answer 81

Distension Resistant to toxicity Renal calyx Urether Bladder Ureter

Question 82

How does the structure of transitional epithelia help its function?

Answer 82

Can stretch/ distend to fill areas (bladder) and allow liquids through (ureter)

Question 83

How is epithelia structure linked to function?

Answer 83

Simple Squamous = their thinness and smooth surface means fluids can move across them with less friction (not the case with stratified) Cuboidal = usually secrete or absorb Columnar = long and have long nuclei; contain sensory receptors; usually secrete or absorb Pseudostratified = have cilia (hair like projections) move things when necessary Transitional = have bulging apical surface of cells- which can distend Simple= thin allowing diffusion across Stratified= usually outer layer is squamous but in a few cases it is columnar or cuboidal; many layers provide better protection as they can resist mechanical stress and dehydration

Question 84

How is the renewal rate for epithelial cells determined?

Answer 84

Depends on location and function of the epithelial cells Always occurs at a constant rate (unless injury leads to acceleration) Can be high! Some epithelia aren't removed but proliferation can be triggered to replace damaged/lost cells

Question 85

What can cause the renewal rate for epithelial cells to increase?

Answer 85

Injury

Question 86

What is the renewal rate for the epidermis (epithelium of the skin)?

Answer 86

28 days from cell division at the basal layer (through differentiation, migration to the exterior, keratinisation and death) to finally being sloughed off at the surface

Question 87

What is the renewal rate of the small intestine epithelia?

Answer 87

4-6 days- replaced from the base of the crypts

Question 88

What are the different types of surface specialisation found on epithelia cells?

Answer 88

Microvilli Cilia Stereocilia

Question 89

What do microvilli look like? Structure related to function?

Answer 89

Brush border- Apical extensions of cell membrane that greatly increase the surface area for selective absorption of intestinal contents (found on simple columnar epithelial cells of small intestine)

Question 90

What do stereocilia look like? Structure related to function?

Answer 90

Very long microvilli, extend from the surface of the ductus deferens of the epididymis (part of the male reproductive system) - may have an reabsorptive function (found on the pseudostratified columnar epithelia of the epididymis)

Question 91

What do cilia look like? Structure related to function?

Answer 91

Extensions from cells that beat in coordinated waves to provide movement of material along the cell surface Elongated, motile, plasmalemma covered extensions of cytoplasm Each one arises from a centriole (contains microtubules: tubulin) 9 pairs of microtubules outside and 2 pairs of microtubules in the middle (found in the pseudostratified epithelia of trachea and simple columnar epithelia of Fallopian tubes)

Question 92

How can you differentiate between cilia, sterocilia and microvilli?

Answer 92

9+2 structure of cilia differentiates it from microvilli Cilia are cytoplasmic extensions whereas microvilli are extensions of apical cell membrane Stereocilia are in fact not cilia but elongated microvilli (so also do not have 9+2 structure)

Question 93

When looking at a slide of stratified epithelial cells, which layer of cells determines the classification?

Answer 93

The most superficial layer

Question 94

Which layer of cells in a stratified structure is in contact with the basement membrane?

Answer 94

ONLY the basal layer

Question 95

What is a mucous membrane?

Answer 95

Made up of surface epithelia, basal lamina, lamina propria and muscularis mucosa (only in alimentary) Lines cavities in contact with the outside - trachea, nasal cavity, respiratory, alimentary, urinary tract SECRETES THICK AND STICKY MUCUS which traps bacteria/ microbes preventing them from entering into the system Endodermal origin

Question 96

What is a serous membrane?

Answer 96

Made up of lining epithelium (mesothelium thus simple squamous), basal lamina and lamina propria Lines closed cavities within the body- pericardial sac, peritoneum, pleural cavity SECRETES SURFACTANT FLUID- thin, smooth and shiny- which lubricates surfaces and reduces friction Mesodermal origin

Question 97

Internal surface of the alimentary tract

Answer 97

Mucosa- surface epithelia, basement membrane (separates ec and ct), lamina propria (supporting ct- lymph node and blood vessels), muscularis mucosa (controls localised movements of mucosa e.g. movement of cilia) Sub mucosa- layer of connective tissue lying below mucosa bearing glands, arteries, veins and nerves Muscularis propria/ externa- larger muscular group; smooth muscle (longitudinal, transverse, circular, oblique); control movements of entire structure (e.g. Peristaltic movements of GI tract) Serosa- external mesothelial lining (simple squamous)/ Adventitia/ rugae/ plicae circulares

Question 98

Where is the muscularis mucosa found?

Answer 98

In the mucosa layer of the internal surface of the ALIMENTARY TRACT ONLY

Question 99

Internal surface of gut wall

Answer 99

Mucosa (simple columnar ec), sub mucosa, muscularis externa (outer longitudinal and inner circular), serosa, mesentery (double layer of peritoneum that suspends the jejunum and ileum from the posterior wall of the abdomen)

Question 100

Internal surface of oesophagus

Answer 100

Mucosa, submucosa (contains mucus secreting glands), muscularis externa (outer longitudinal and inner circular), Adventitia (thin outermost layer of connective tissue)

Question 101

Internal surface of stomach

Answer 101

Mucosa (secretes acid, gastrin and digestive enzymes; simple columnar ec), submucosa, muscularis externa (oblique, circular and longitudinal- moves food along in peristalsis), rugae (folds of gastric mucosa- forms ridges in empty stomach)

Question 102

Internal surface of the jejunum

Answer 102

Mucosa (simple columnar epithelium), submucosa, muscularis externa (outer longitudinal and inner circular), plicae circulares (circular folds of mucosa and submucosa that project into the gut lumen)

Question 103

Internal surface of large intestine

Answer 103

Mucosa (crypts of lieberkuhn- peyers patch- lymphoid tissue) (simple columnar ec), submucosa, muscularis externa

Question 104

Internal surface of the respiratory tract

Answer 104

Mucosa- epithelial cell, basal lamina, lamina propria (NO MUSCULARIS MUCOSA) Sub mucosa

Question 105

Internal surface of tracheal wall

Answer 105

``` Mucosa (ciliated pseudostratified columnar ec) Submucosa Cartilage ring (c shaped) Fibroelastic membrane (contains tracheal muscle) ```

Question 106

Internal surface of bronchus

Answer 106

``` Mucosa (ciliates pseudostratified columnar ec) Sub mucosa (sero mucous glands) Cartilage (crescent shaped and near to artery and veins) ```

Question 107

Internal surface of bronchioles

Answer 107

Mucosa (ciliated simple columnar) Clara cells (secrete surfactant) Alveoli nearby NO CARTILAGE- held open by elastic fibres in alveoli

Question 108

Internal surface of alveoli

Answer 108

Type 1 cells - squamous 90% - gas exchange in capillaries Type 2 cells - cuboidal 10% - produce surfactant Macrophages - phagocytise particles Surrounded by basket work of capillaries and elastic fibres Gas exchange occurs across blood brain barrier

Question 109

Internal surface of urinary tract

Answer 109

Mucosa- epithelial cell, basal lamina, lamina propria (NO MUSCULARIS MUCOSA) NO SUBMUCOSA Muscularis externa

Question 110

Internal surface of ureter

Answer 110

Mucosa (transitional ec) Muscularis externa (circular) Adventitia

Question 111

Internal surface of bladder

Answer 111

Mucosa (transitional ec) Muscularis externa (circular, oblique and longitudinal) Adventitia

Question 112

Internal surface of urethra

Answer 112

``` Mucosa (transitional ec)/ penile urethra= stratified columnar ec Muscularis externa (inner circular and outer longitudinal ) Adventitia ```

Question 113

Define a gland

Answer 113

An epithelial cell or an aggregate of cells specialised for secretion

Question 114

How can glands be classified?

Answer 114

By destination of secretion- exocrine (secrete through ducts directly onto target) endocrine (secrete into bloodstream- ductless) By structure of gland- Unicellular (e.g. goblet cell) or multicellular (e.g submandibular) Acinar (bulbed glands with myoepithelial lining for contraction e.g. Sebaceous, mammary gland) or tubular (e.g. Intestinal glands, merocrine sweat glands, gastric glands, mucous glands of oesophagus, mucous glands, testes) Coiled (e.g. merocrine sweat gland) or branched (e.g. Gastric glands, mucous glands of oesophagus, sebaceous glands) Simple (e.g. intestinal glands merocrine sweat glands, sebaceous glands, gastric glands, mucous glands of oesophagus) or compound (e.g. mucous glands, testes, mammary glands, salivary glands, pancreas) Main, interlobular, intralobular and intercalated By nature of secretion- Mucous gland- brunners gland Serous gland- parotid gland, pancreas Seromucous gland- submandibular (mostly serous) and sublingual (mostly mucous) By method of discharge- Merocrine (sweat glands) Apocrine (mammary gland) Holocrine (sebaceous gland)

Question 115

What does exocrine mean?

Answer 115

Gland secretes directly into target through ducts

Question 116

What does endocrine mean?

Answer 116

Ductless | Gland secretes into bloodstream

Question 117

What does acinar mean?

Answer 117

Describes structure of gland Small sac or cavity surrounded by secretory cells of a gland Bulbed glands with myoepithelial lining for contraction

Question 118

What does tubular mean?

Answer 118

Describes structure of gland | Contains tubules- small cylindrical hollow structures

Question 119

What does simple mean (wrt glands)?

Answer 119

Single duct and thus exocrine

Question 120

What does compound mean (wrt glands)?

Answer 120

Many branched ducts (branches are branched)

Question 121

What defines a mucous gland?

Answer 121

Nature of secretion Secretes mucus rich in mucins (highly glycosylated proteins) Stain poorly in H&E sections- appear light E.g. Brunners gland

Question 122

What defines a serous gland?

Answer 122

Nature of secretion Secretions often watery and enzyme rich (free of mucus) Eosinophilic- appear pink (darker) in H&E sections E.g. Parotid gland

Question 123

What defines seromucous glands?

Answer 123

Mixed serous and mucous glands Submandibular and sublingual glands

Question 124

What is a serous demilune?

Answer 124

When the seromucous cell undergoes artefactual distortion due to dehydration in preparation- so appear as serous half moons as serous (darker) portion of cell is pushed to sides to form a half moon shape

Question 125

Describe merocrine secretion

Answer 125

Exocytosis of small membrane bound vesicle, commonly proteins from the cell Membrane bound vesicle approaches cell surface and fuses with plasma membrane Contents of vesicle are in continuity with the extra cellular space Plasma membrane is very slightly larger Membrane retrieved stabilising cell surface area Sweat glands, salivary glands, pancreas

Question 126

Describe apocrine secretion

Answer 126

Involves process of exocytosis of a free structure from the cell Non membrane bound structure approaches cell surface Makes contact and pushes up apical membrane Thin layer of apical cytoplasm drapes around droplet Membrane surrounding the droplet pinches off from cell Plasma membrane is very slightly smaller Membrane added to regain original surface area Mammary glands

Question 127

Describe holocrine secretion

Answer 127

Entire cell disintegrates to release its contents Disintegration of entire cell Release of contents Discharge of whole cell Sebaceous glands

Question 128

List the exocrine glands you need to be able to identify

Answer 128

``` Goblet cells in jejunum and colon Parotid glands Submandibular lands Liver (exo and endo) Pancreas acinar (has exo and endo) ```

Question 129

What is the location and function of myoepithelial cells in glands?

Answer 129

In lining of acinar glands- assist with secretion E.g. In mammary glands- (compound acinar)

Question 130

List the endocrine glands you need to be able to identify

Answer 130

Thyroid gland Parathyroid gland Adrenal gland Pancreas- islet of lagerhans (exo and endo)

Question 131

Describe endocytosis

Answer 131

Process of engulfing material initially outside the cell | Opposite of exocytosis (merocrine)

Question 132

What is transepithelial transport?

Answer 132

Coupling of endocytosis and exocytosis (merocrine) When a molecule is too large to penetrate membranes it can be shunted across from one component of the body to another. - material is endocytosed at one surface of the cell - transport vesicle shuttles it across the cytoplasm - material/vesicle is then exocytosed at the opposite surface E.g calcium transport across epithelial cells in the gut- 3 ways: with ATP, transcellular transport or endo/exo with a CaBP complex

Question 133

What is the importance of glycosylation of newly synthesised proteins in the Golgi apparatus?

Answer 133

O linked glycosylation occurs in Golgi (where sugars are added to hydroxyl group of serine or threonine) [REMEMBER: N linked glycosylation occurs in ER where sugars are built up on the dolichol phosphate carrier molecule on the membrane and then transferred to the amide group of an asparagine] Branching sugars offer complex shapes for interactions in the glycocalyx Enzymatic destruction if this layer alters specificity based properties of cells: -adhesion to substrates and neighbouring cells -communication with neighbouring cells -contact inhibition of movement and division -mobility of cells Sugars make the molecules more specific- so secretions can communicate effectively with outside world

Question 134

What are some simple mechanisms of control of secretion from glands?

Answer 134

Nervous- SNS stimulates adrenal medulla to secrete adrenaline Endocrine- ACTH stimulates adrenal cortex (zona fasisculata) to secrete cortisol Neuroendocrine- nervous cells and CRH of hypothalamus control ACTH secretion from Anterior pituitary Negative feedback- inhibitory effect if high T3 and T4 hormones on TsH synthesis by anterior pituitary/ cortisol on ACTH/ calcium on PTH (Metabolism)

Question 136

Define connective tissue

Answer 136

Tissue of mesodermal origin with three basic components- cells, extra cellular fibres and ground substance

Question 137

What are the functions of connective tissue?

Answer 137

``` Structure- ligaments and tendons Infection defence Cushioning and support- submucosa Attachment and binding Diffusion medium- blood Injury repair- fractures (cartilage--> bone) ```

Question 138

What are some examples of connective tissue?

Answer 138

Submucosa- alimentary canal (dense irregular or loose) Ligaments and tendons- tensile strength (dense regular) Dura mater, periosteum (covers outer surface of bone), perichondrium (surrounds cartilage of developing bone)- (dense irregular)

Question 139

What CT are found in cartilage, bone, muscle and nerves?

Answer 139

Epimysium/ epineurium | Perichondrium/ periosteum/ perimysium/ perineurium Endosteum/ endomysium/ endoneurium

Question 140

What are the common cells found in connective tissue and what are their functions?

Answer 140

Fibroblast- synthesis of collagen, elastic, reticular fibres and most of the ground substance (depends on Vit C to function) Adipocytes- responsible for storage and metabolism of fats; may form small clusters in loose CT; protects, insulates and cushions organs of the body Macrophages- derived from monocytes in bone marrow; migrate to connective tissue and function in ingesting (phagocytosing) foreign particulate matter Mast cells- secrete histamine in allergic reactions or asthma Myofibroblasts- fibroblasts with additional contractile function Chondrocytes- inactive cartilage synthesising (chondroblast) cells Osteocytes- inactive bone synthesising (osteoblast) cells Plasma cells- secrete antibodies in infection Fibrocytes- inactive fibre synthesising (fibroblasts) cells

Question 141

What do fibroblasts depend on to function?

Answer 141

Vitamin C

Question 142

What do fibroblasts, adipocytes, mast cells, chondroblasts, osteoblasts etc look like?

Answer 142

Google it/ ppt

Question 143

What three fibres are found in connective tissue?

Answer 143

Collagen, reticular, elastin

Question 144

What makes up the extra cellular matrix of connective tissue?

Answer 144

Ground substance and collagen, elastic and reticular fibres that lie within it and extra cellular fluid

Question 145

Describe the structure and function of collagen

Answer 145

Bundles of non elastic fibres of varied thickness Most abundant protein (25-30% of all protein) Composed of 3 alpha chains of tropocollagen (varies with type of collagen e.g. Type 1 = 2 alpha and 1 beta) Every 3rd amino acid is glycine (smallest amino acid- folds into the inside of the triple helix of 3 chains) gly-x-y X and y are most commonly proline- (helix breaker prevents individual chains from forming individual helices) and hydroxyproline/ hydroxylysine- (can form hydrogen bonds which hold the three chains together and maintain the stability of the tropocollagen molecule) and lysine Requires vitamin c to hydroxylate lysine and proline Constitutively secreted protein Synthesis occurs on RER of fibroblast cells (MGD collagen formation link)

Question 146

Where is type 1 collagen found?

Answer 146

Skin dermis

Question 147

Where is type 2 collagen found?

Answer 147

Ears- hyaline and elastic cartilage

Question 148

Where is type 3 collagen found?

Answer 148

Reticular fibres- intestine, skin, uterus, basement membrane

Question 149

Where is type 4 collagen found?

Answer 149

Lens of the eye

Question 150

Where is type 5 collagen found?

Answer 150

Placenta

Question 151

What are some special names for macrophage cells?

Answer 151

Kupffer cells found in the liver Microglia found in the CNS Osteoclasts found in the bone

Question 152

Where are reticular fibres found?

Answer 152

Lymph nodes

Question 155

Where are elastic fibres found?

Answer 155

Lungs

Question 157

What is the ground substance?

Answer 157

Gel like matrix in which the fibres and cells are embedded- through which extracellular fluid diffuses

Question 158

What is the structure and function of the ground substance in connective tissues?

Answer 158

Viscous- lubricant and barrier to invaders Composed of glycosamionglycans (GAGs) (hexosamine and hexuronic acid), hyaluronic acid, proteoglycans and glycoproteins In the ground substance each hyaluronic acid molecule has many proteoglycan molecules branching off it Each individual proteoglycan molecule has many GAGs branching off it GAGs are negatively charged and so attract water molecules keeping the ground substance hydrated =hyaluronate proteoglycan aggregate

Question 159

Describe the four broad classifications of connective tissue

Answer 159

Embryonic- mesenchyme and mucus Supporting- bone and cartilage Proper- loose, dense regular, dense and reticular Specialised- adipose, lymphatic and haemopoetic tissue, blood, cartilage and bone

Question 160

Describe mesenchyme connective tissue

Answer 160

Embryonic ct Cells are spindle shaped with large nuclei ECM contains reticular fibres

Question 161

Describe mucus connective tissue

Answer 161

``` Embryonic ct Whaton's jelly Fibroblast cells with oval nuclei ECM contains collagen bundles arranged irregularly LOOSE Umbilical cord ```

Question 162

Describe loose connective tissue

Answer 162

Made up of loosely packed fibres and cells separated by amorphous ground substance Cells include fibroblasts, macrophages, mast cells, fat cells, plasma cells ECM consists of collagen and elastic fibres and watery ground substance Support and frame work of internal structures Forms walls and rods that make up the framework inside organs and adipose tissue- adipose, blood, areolar ct, reticular tissue

Question 163

Describe adipose tissue

Answer 163

Loose ct Adipose cells occur singly or in groups between collagen fibres When they make up most of the cells in a tissue the tissue is termed adipose tissue Nuclei are often compressed against cell membrane

Question 164

Describe reticular tissue

Answer 164

Loose ct | Made up of lots of type 3 collagen and form framework of lymphoid tissues and liver

Question 165

Describe reticular connective tissue

Answer 165

Type of loose ct Cells consist of reticular cells, large ovals nuclei, lymphocytes, macrophages ECM consists of reticular fibres Found in liver kidney spleen lymph nodes and bone marrow

Question 167

What is areolar ct?

Answer 167

A type of loose ct Found in sub mucosa, deep under the skin, beneath ecs of mucous membranes, below mesothelium and peritoneum, associated with Adventitia of blood vessels, surrounding parenchyma of glands Contains fibroblasts, macrophages, mast cells, abundant collagen fibres and less abundant elastic fibres

Question 168

Describe dense connective tissue

Answer 168

Closely packed fibres with proportionally fewer cells and less ground substance Achieve mechanical support and transmit forces

Question 169

Describe dense regular connective tissue

Answer 169

Where fibres are arranged in parallel to provide maximum tensile strength Cells include flattened fibroblasts in parallel rows ECM consists of parallel rows of densely packed collagen

Question 170

Describe two examples of dense regular connective tissue

Answer 170

Ligaments- collagen fibres interspersed with fibroblasts Tendon- collagen fibres interspersed with flattened fibroblasts- fascicles (bundles of collagen and fibroblasts) are separated by endotendineum (loose ct) and held together by peritendineum Fibrous sheath surrounds whole tendon

Question 171

Describe dense irregular connective tissue?

Answer 171

Interwoven bundles of collagen which criss cross each other in many directions- counteracts multi directional forces to which the tissues are subjected Cells include fibroblasts and macrophages ECM consists of thick wavy bundles of collagen fibres as well as elastic and reticular fibres

Question 172

What are the specialised connective tissues?

Answer 172

``` Blood Adipose tissue Cartilage Bone Lymphatic tissue Haemopoetic tissue ```

Question 173

List some loose connective tissues

Answer 173

Adipose tissue | Blood

Question 174

List some dense regular connective tissues

Answer 174

Tendons | Ligaments

Question 175

List some dense irregular connective tissue

Answer 175

Dermis, periosteum, perichondrium, dura mater

Question 176

List where reticular connective tissues can be found

Answer 176

``` Structural framework of: Liver Kidney Spleen Lymph nodes Bone marrow ```

Question 177

What 6 diseases are related to connective tissue?

Answer 177

``` Systematic sclerosis Keloid Vitamin C deficiency Marfan's syndrome Ethlers Danlos disease Edema ```

Question 178

What is systematic sclerosis?

Answer 178

Ct Organs have excessive accumulation of collagen (fibrosis) Occurs in skin, digestive tract, muscles and kidneys =hardening and functional impairment

Question 179

What is a keloid?

Answer 179

Ct | Scar of skin cause by abnormal amounts of collagen

Question 180

What is vitamin C deficiency?

Answer 180

Ct Scurvy Fibroblasts unable to function leading to defective collagen synthesis and degeneration of connective tissue Enzyme prolyl hydroxylase (relies on vitamin C and Fe2+ for functioning) cannot function - cant hydroxylate proline residues in collagen - so lack of H bonds means tropocollagen triple helices are weak Periodontal ligament (with normal high collagen turnover) is affected in scurvy- loosening of teeth in sockets and eventual loss and bleeding gums

Question 181

What is Marfan's syndrome?

Answer 181

Ct Defect in gene coding for fibrillin (found in elastic fibres) Elastic fibres underdeveloped Bulges form in artery walls, causing a smaller lumen and increasing blood pressure As a result large elastic arteries (such as aorta) rupture Tall Arachnodactyly Frequent joint dislocation

Question 182

What is skin?

Answer 182

Continuous external surface which covers the outside of the body Has keratinised stratified squamous epithelia (made up of mainly keratinocytes and their products) Arranged in layers of connective tissue over the epidermis, dermis and hypodermis

Question 183

What causes skin to vary?

Answer 183

``` Colour Hair Thickness Laxity/ wrinkling Oiliness ```

Question 184

How does skin vary with colour?

Answer 184

Ethnicity Site- lips areolae UV exposure

Question 185

How does skin vary with hair?

Answer 185

Site of hair- e.g little hair found in palmar surfaces of hands and feet but found on plantar surfaces Gender- more profuse body and facial hair in men Age- baldness in men and greeting in both sexes Ethnicity- colour and character

Question 186

How does skin vary with thickness?

Answer 186

Site- scalp vs ball of foot vs eyelid

Question 187

How does skin vary with oiliness?

Answer 187

Puberty and site

Question 188

How can variations in skin influence the susceptibility to and/or manifestations of skin disease?

Answer 188

Vitiligo (depigmentation of skin) much less of a problem in fair skinned individuals as its barely visible Alopecia areata/ totalis - autoimmune response leading to hair loss Fair skinned people are more susceptible to UV induced acute sunburn, freckling, ageing and skin cancer- especially thouse with red hair and blue eyes Acne is common through puberty

Question 189

What are the three layers that make up the skin?

Answer 189

Epidermis dermis and hypodermis

Question 190

What are the four layers that make up the epidermis of the skin?

Answer 190

``` Horny layer (stratum corneum) Granular layer (stratum granulosum) Prickle cell layer (stratum spinosum) Basal layer (stratum basale) ```

Question 191

What does the horny layer of skin consist of?

Answer 191

Layers of flattened corneocytes (dead keratinocytes) and keratin

Question 192

What does the granular layer of skin consist of?

Answer 192

Contains keratohyalin granules which consist of keratins, other fibrous cross link proteins (such as filaggrin- which aggregates keratins; and involucrin- which forms a major part of corneocytes envelope) and enzymes which degrade phospholipid bilayer (phospholipases)

Question 193

What does the prickle cell layer of skin consist of?

Answer 193

``` Prickle cells joined by prickle like desmosomes (intracellular junctions) Langerhans cells (dendritic cells with a bone marrow origin; scattered in prickle cell layer; mediate immune reactions and present antigens to T lymphocytes) ```

Question 194

What does the basal layer of skin consist of?

Answer 194

Melanocytes (dendritic cells with a neural crest origin; intervals along basal layer; produce melanin- pigment that gives skin it's colour*) difficult to see without special stains Site of keratinocyte mitosis *darker skin= more melanin production NOT more melanocytes

Question 195

What is the dermo-epidermal junction?

Answer 195

Epidermal basement membrane below the basal layer of the epidermis- best seen with a PAS stain

Question 196

Why is the dermo epidermal junction best seen with a PAS stain?

Answer 196

Stains carbohydrates and glycoproteins magenta | It's a basement membrane containing carbohydrates and glycoproteins

Question 197

Why is the dermo-epidermal junction/ epidermal basement membrane important in prognosis?

Answer 197

Retention of malignant melanocytes above the membrane is associated with a good prognosis in melanoma If malignant melanocytes break through membrane= poorer prognosis

Question 198

What are langerhans cells and where are they found?

Answer 198

Langerhans cells (dendritic cells with a bone marrow origin; scattered in prickle cell layer; mediate immune reactions and present antigens to T lymphocytes)

Question 199

What are melanocytes and where are they found?

Answer 199

Melanocytes (dendritic cells with a neural crest origin; intervals along basal layer; produce melanin- pigment that gives skin it's colour*) difficult to see without special stains *darker skin= more melanin production NOT more melanocytes

Question 200

Describe the process of keratinocyte differentiation in the epidermis

Answer 200

Basal layer- keratinocytes undergo mitosis and cell division Prickle cell layer- keratinocytes undergo terminal differentiation/ lose ability to divide/ actively produce proteins (keratins= heterodimeric fibrous proteins which contribute to epidermis strength) Granular layer- keratinocytes lose their plasma membranes and begin differentiating into corneocytes Horny layer- cells lyse to release keratin

Question 201

What is the transit time of s keratinocyte from the basal layer to the horny layer?

Answer 201

30-40 days

Question 202

What type of connective tissue is the dermis?

Answer 202

Dense irregular connective tissue

Question 203

What does the dermis consist of?

Answer 203

Highly vascularised- lots of blood and lymph vessels - so it can supply the avascularised epidermis Deeper the dermis the larger the blood vessels --> birth marks Fibroblasts- spindle shaped cells which make the ECM- collagen and elastic fibres --> keloid Mast cells- distributed around blood vessels; contains cytoplasmic histamine granules --> local oedema/ urticaria and angio-oedema in skin Nerves- sensory- important in transmitting skin sensation

Question 204

What are birthmarks?

Answer 204

Malformations of blood vessels in the dermis

Question 205

Name 4 skin appendages

Answer 205

Hair Sebaceous glands Sweat glands Nails

Question 206

How are hair follicles connected to sebaceous glands?

Answer 206

Sebaceous glands are branched acinar exocrine glands, which have a duct that communicates with the hair follicles. Sebaceous glands operate by holocrine secretion

Question 207

What type of gland are sebaceous glands?

Answer 207

Branched Acinar Exocrine Holocrine

Question 208

Where are sebaceous glands located in the skin?

Answer 208

Dermis, with a duct going into a hair follicle

Question 209

Where are hair follicles located in the skin?

Answer 209

epidermis

Question 210

Where are sweat glands located in the skin?

Answer 210

Epidermis and Dermis

Question 211

What are eccrine sweat glands?

Answer 211

Major sweat glands of the body Found in most of the skin Produce clear odourless merocrine secretion (water and NaCl- reabsorbed to reduce salt loss) Active in thermoregulation Controlled by hypothalamus Consist of an intraepidermal spiral duct, straight dermal portion and a coiled acinar potion in dermis

Question 212

What are apocrine sweat glands?

Answer 212

Large sweat glands Abundant in Axillae, genital and submammary areas No function of value Produce odourless, protein rich, apocrine secretion- digestion by cutaneous microbes produces body odour Duct joins onto a hair follicle duct

Question 213

What type of connective tissue is the hypodermis?

Answer 213

Loose connective tissue composed mainly of adipose tissue

Question 214

What is Ethlers Danlos disease?

Answer 214

Ct Deficiency in collagen type III and hence reticular fibre Causes ruptures in tissues with a high reticullin content ( structural framework of liver kidney spleen bone marrow and lymph nodes)

Question 215

What is subcutaneous fat?

Answer 215

Found beneath the skin mainly in the hypodermis | Composed of adipocytes, grouped in lobules surrounded by connective tissue- adipocytes tissue= loose connective tissue

Question 216

What is oedema?

Answer 216

Ct Mast cells release histamine granules Increases permeability of capillaries Promotes flow of blood out of blood stream and into tissue spaces Results in excess accumulation of EC fluid and thus gross swelling Especially apparent in loose ct

Question 217

What are some examples of dense irregular connective tissue?

Answer 217

Dermis of skin, large septa (walls) and trabecular (rods) of many organs, periosteum, perichondrium and dura mater

Question 218

Describe the structure and function of reticular fibres

Answer 218

Thin branching carbohydrate coated fibres composed of type III collagen Form delicate network around smooth muscle cells, certain epithelial cells , blood vessels, adipocytes and nerve fibres (seban) Make a structural framework around certain organs such as the liver, spleen, bone marrow and lymphoid organs (When stained with silver- appear brown with light microscope due to carbohydrate coat)

Question 220

Describe the structure and function of elastic fibres

Answer 220

Elastin surrounded by microfibrillous component consisting of fibrillin Similar to collagen but contains same amount of hydroxyproline but different amount of hydroxylysine- so thinner Elasticity of elastin is because of high lysine content- 4 lysine amino acids from different chains form covalent cross links with one another- highly deformable and can stretch as tensile forces are applied

Question 221

What are the main functions of skin?

Answer 221

Barrier Sensation Thermoregulation Psychosexual communication

Question 222

How does skin act as a barrier?

Answer 222

Horny layer of epidermis forms a major barrier preventing percutaneous absorption of exogenous substrates Studied in detail as horny layer barrier must be overcome during percutaneous absorption of drugs Horny late barrier can be disrupted by many diseases- psoriasis

Question 223

How does skin function with sensation?

Answer 223

Sensory nerves in dermis Leprosy Diabetic sensory neuropathy Both diseases of peripheral nerves

Question 224

How does the skin function with thermoregulation?

Answer 224

``` Vascular thermoregulation (dilation leads to heat loss and constriction leads to pallor and heat conservation) Thermoregulation eccrine sweating (evaporation of eccrine sweat causes cooling) Both maintain body temperature ```

Question 225

How does skin function with psychosexual communication?

Answer 225

Skin and its appearance are manipulated in a many ways as a means of communication and expression (tattoos and piercings)

Question 226

What 5 diseases are associated to skin diseases?

Answer 226

``` Psoriasis Malignant melanoma Vitiligo Alopecia (areata or totalis) Acne ```

Question 227

What is psoriasis?

Answer 227

Disorder of epidermal growth and differentiation There is extreme proliferation of the basal layer The prickle cell layer thickens The horny layer is excessively produced Leads to excessive scaling of skin surface

Question 228

What is malignant melanoma?

Answer 228

Aggressive tumour of melanocytes in basal layer Can break through the epidermal basement membrane /dermo-epidermal junction= poor prognosis ABCDE mole classification

Question 229

What is vitiligo?

Answer 229

Autoimmune disease Immune system attacks melanocytes usually in symmetrical localised areas of skin Causing well demarcated pigmentation (cause is unknown- could be that process is under neural control as melanocytes are embryonic ally derived from the neural crest)

Question 230

What is alopecia areata?

Answer 230

Autoimmune attack against hair follicles

Question 231

What is acne?

Answer 231

Sebaceous glands produce excessive amounts of sebum (e.g. during puberty) Duct between sebaceous glands and hair follicles becomes obstructed Normally harmless bacteria on skin surface, can infect a blocked follicle- causing pus filled papules/ cysts

Question 232

What is vellus hair?

Answer 232

Short, fine, light coloured and barely noticeable hair that develops on most of a persons body during childhood

Question 233

What are terminal hairs?

Answer 233

Thick, long and dark compared with vellus hair During puberty the increase in androgen hormones causes vellus hair to be replaced by terminal hair in certain parts of the body

Question 234

Define cartilage

Answer 234

Specialised avascular connective tissue with a mesenchymal origin (from mesoderm)

Question 235

What does cartilage generally consist of?

Answer 235

Cells: chondrocytes (produce and maintain ECM) , chondroblasts (spindle shaped- can become fibroelastic and crowd perichondrium; produce and maintain ECM), fibroblasts (cells that produce fibres in perichondrium) ECM: type 2 collagen, hyaluronic acid, proteoglycan monomers, GAGs Remember perichondrium is dense irregular connective tissue

Question 236

How is the ECM of cartilage adapted to its function?

Answer 236

Negatively charged GAGs attract water- so keep gel hydrated High GAGs : collagen (II) ratio per its the ready diffusion of substances between chondrocytes and blood vessels surrounding the cartilage Large amounts if hyaluronic acid makes ECM solid, firm and pliable- so resistant to repeated application of pressure

Question 237

What is the perichondrium?

Answer 237

Dense irregular connective tissue that surrounds the cartilage

Question 239

What are the 3 main types of cartilage?

Answer 239

Hyaline, elastic and fibrocartilage

Question 240

What is the function of hyaline cartilage?

Answer 240

Support and movement

Question 241

Where is hyaline cartilage found?

Answer 241

Respiratory pathways, ends of long bones (articulating surfaces), epiphyseal plate, anterior ends of ribs, foetal skeleton

Question 242

Whatis the structural composition of elastic cartilage?

Answer 242

Cells: chondrocytes ECM: pgm, ha, GAGs, collagen (II) AND ELASTIN Perichondrium present

Question 243

What is the function of elastic cartilage?

Answer 243

Support and shape

Question 244

Where is elastic cartilage found?

Answer 244

Pinna of ear, epiglottis, eustacian tube

Question 245

What is the structural composition of fibrocartilage?

Answer 245

Cells: chondrocytes AND FIBROBLASTS ECM: pgm, ha, GAGs, collagen (II) and collagen (I) Perichondrium NOT PRESENT

Question 246

What is the function of fibrocartilage?

Answer 246

Shock absorber

Question 247

Where is fibrocartilage found?

Answer 247

Intervertebral discs, knee meniscus, pubic symphysis, portions of tendons

Question 248

Which cartilages can calcify in old age/ disease?

Answer 248

Hyaline cartilage can calcify

Question 249

What is the relevance of cartilage in osteoarthritis?

Answer 249

Joint pain occurs due to erosion at the hyaline cartilage articulating surfaces on ends of bone

Question 250

What is cauliflower ear?

Answer 250

Perichondrium haematoma which causes necrosis and fibrosis of cartilage

Question 251

What is an embryo's skeleton made of?

Answer 251

In 5th week of development- Hyaline cartilage | until it is replaced with bone

Question 252

What remnants of the cartilage in the embryo exist in humans?

Answer 252

Epiphyseal growth plates and articulating surface cartilage- which eventually is converted to bone

Question 253

What is the clinical relevance of hyaline cartilage?

Answer 253

Can calcify/ossify in old age and disease. Susceptible to degenerative ageing process- normal but accelerates in ageing via calcification of matrix due to increase in number and size if chondrocytes and cell death. Joint pain can be the result of articular cartilage erosion on the ends of bones (osteoarthritis) Rheumatoid arthritis occurs when secondary destruction of articular cartilage occurs by granulating synovial membrane tissue

Question 254

What is the clinical relevance of elastic tissue?

Answer 254

Does not calcify/ ossify in old age

Question 255

What is the clinical relevance of fibrocartilage?

Answer 255

Rupture of annulus fibrosus (invertebral disc capsule) leads to slipped disc Tearing of menisci

Question 256

What are the two stages of cartilage growth?

Answer 256

Appositional growth | Interstitial growth

Question 257

What is appositional growth?

Answer 257

Fibroblast cells of perichondrium give rise to flat newly formed chondroblasts which secrete ECM and round up to develop onto chondrocytes Cartilage grows from the periphery- wide ways At the edge of cartilage mass- appositional growth adds various protuberances that will eventually be replaced by bone to create the final shape Mainly in mature cartilage

Question 258

What is interstitial growth?

Answer 258

Chondrocytes deeper in the cartilage divide and give rise to isogenous groups which deposit further matrix These cells separate as they lay down further matrix Cartilage grows long ways In middle of cartilage mass- interstitial grown increases its overall size Mainly in immature cartilage

Question 259

What is the structural composition of hyaline cartilage?

Answer 259

Cells: chondrocytes ECM: pgm, ha, GAGs, collagen (II) Perichondrium present (except on articulating surfaces)

Question 260

Amongst the isogenous groups of chondrocytes what is the interterritorial and territorial matrix?

Answer 260

Interterritorial matrix is the lighter stained areas Territorial matrix is the darker stained areas that contain more highly sulphated substances in ground substance - generally closer to isogenous groups

Question 261

What cells do not contain mitochondria?

Answer 261

Red blood cells

Question 262

What cells don't have a nucleus?

Answer 262

Red blood cells

Question 263

What are the characteristic features of bone in the body?

Answer 263

Hardest bone in the body Vascularised- supplied with blood and lymph vessels and nerves (so sensitive to pain- esp. in periosteum) Dynamic- can withstand compression, stress and deformation Type of connective tissue- so contains characteristic cells, fibres and ground substance

Question 264

What are the 4 general functions of all bone?

Answer 264

Support Protection Mineral storage (calcium and phosphate) Haemopoeisis- formation of blood cells (bone contains the bone marrow- site of haemopoiesis)

Question 265

Is bone vascularised? How does this affect it?

Answer 265

Yes- helps with repair

Question 266

Is cartilage vascularised? How does this affect it?

Answer 266

No- so difficult to repair

Question 267

What two forms can bone have?

Answer 267

Spongy/ cancellous bone | Compact/ dense bone

Question 268

What is the general arrangement of these two forms of bone?

Answer 268

Spongy is normally surrounded by compact

Question 269

What is the arrangement of compact/ dense bone?

Answer 269

Concentric lamellae with central vertical Haversian canals (bearing blood and lymph vessels and nerves) which communicate via horizontal Volkmann's canals} collectively all known as an osteon/ haversian system

Question 270

What is a Haversian canal?

Answer 270

Vertical canals found in the centre of an osteon of compact bone bearing blood vessels, lymph vessels and nerves

Question 271

What is a Volkmann's canal?

Answer 271

Horizontal canals which connect Haversian canals in different osteons Bear blood, lymph vessels and nerves

Question 272

What is an osteon?

Answer 272

An entire Haversian system consisting of a Haversian canal (containing blood, lymph vessels and nerves) surrounded by concentric lamellae of bone

Question 273

What is interstitial lamellae?

Answer 273

Adjoining lamellae found between osteons (so not in concentric circles) Usually the remnants of remodelled bone

Question 274

What is the arrangement of spongy/cancellous bone?

Answer 274

Mesh work of trabeculae (thin bits of bone) filled in with marrow

Question 275

What is bone marrow?

Answer 275

Flexible tissue in interior of bones Red bone marrow- red blood cell synthesis Yellow bone marrow- contains adipose tissue Marrow is confined within a thin cellular layer- endosteum Site of B cell production and haemopoisis

Question 276

What is endosteum?

Answer 276

Thin cellular layer of connective tissue that lines the trabeculae of spongy bone and confines the loose bone marrow

Question 277

What is periosteum?

Answer 277

Double layer of connective tissue that covers the external surface of an entire bone

Question 278

What does bone consist of?

Answer 278

Cells- osteoblasts, osteoclasts and osteocytes ECM- fibres and ground substance- rigid calcified matrix (65% inorganic calcium phosphate and calcium carbonate salts= hydroxyapatite crystals ; 35% osteoid- organic collagen, non collagenous proteins and water) Cells embedded in a calcified matrix- matrix consists of collagen and hydroxyapatite crystals

Question 279

What are osteocytes?

Answer 279

Bone cells- found in lacunae cavities; maintain bone; formed when osteoblasts that release their matrix are entombed to form osteocytes

Question 280

What are osteoblasts?

Answer 280

Builder bone cells Synthesise the osteoid matrix (Organic portion of ECM ) When stimulated by PTH Secrete cytokines- stimulate differentiation of osteoblasts into osteoclast and hence stimulate osteoclast activity (METABOLISM) Can differentiate into other bone cells --> osteocytes and osteoclastsc

Question 281

What are osteoclasts?

Answer 281

Claw away at bone Large multinucleated cells from monocytes that digest bone When stimulated by PTH and cytokines produced by osteoblasts- will reabsorb bone- releasing calcium into blood

Question 282

What gives bone its hardness and rigidity?

Answer 282

Inorganic calcium and phosphate salts and collagen

Question 283

What gives bone it's flexibility?

Answer 283

Collagen

Question 284

How are calcium and phosphate stores in the matrix regulated?

Answer 284

Calcium and phosphate stores in the matrix are either stored in the bone or released into the blood to maintain constant levels of calcium and phosphate in the blood plasma Parathyroid hormone- released when blood calcium concentration is lower than normal- stimulates osteoclast activity- increases bone reabsorption Calcitonin- released when blood calcium concentration is higher than normal- inhibits osteoclast activity- decreases bone reabsorption

Question 285

What are some functions of calcium which deem it necessary for blood calcium concentrations to be controlled?

Answer 285

Sickle contraction Blood coagulation Cell membrane permeability Nerve impulse transmission (parathyroid)

Question 286

What are the 5 main types of Bone in the human body?

Answer 286

Long bones, short bones, flat bones, irregular bones, sesmoid bones

Question 287

What are the characteristic features of long bone?

Answer 287

Longer than it is wide Compact bone surrounds central spongy bone Both ends have Growth plates- epiphysis Both ends have hyaline cartilage- acts as protection and support

Question 288

What is the function of long bone? Where is long bone found?

Answer 288

Provide shape for our bodies, help in movement with muscles ``` Femur Humerus Tibia Metacarpals (lower bone of fingers) Metatarsals (lower bones of toes) Phalanges ```

Question 289

What are the characteristic features of short bone?

Answer 289

As wide as they are long | Thin layer of compact bone surrounds spongy bone (containing lots of bone marrow)

Question 290

What is the function of short bone? Where is short bone found?

Answer 290

Provide support and stability with little movement Carpals (wrist) Tarsals (ankle)

Question 291

What are the characteristic features of flat bone?

Answer 291

Strong flat plates of bone Anterior and posterior surfaces composed of compact bone which consists of spongy bone in the centre (and varying amounts of bone marrow)

Question 292

What is the function of flat bone? Where is flat bone found?

Answer 292

Protection for vital body organs, base for muscular attachment ``` Scapula (shoulder blades) Sternum (breast bone) Cranium (skull) Coxae (hip bones) Pelvis Ribs ```

Question 293

What are the characteristic features of irregular bone?

Answer 293

Non uniform shape- fit into no other category | Primarily consist of thin layer of compact bone surrounding spongy bone

Question 294

What is the function of irregular bone? Where is irregular bone found?

Answer 294

No universal functions Vertebrae Sacrum Mandible (lower jaw)

Question 295

What are the characteristic features of sesmoid bones?

Answer 295

Short or irregular bones embedded in a tendon where it passes over a joint

Question 296

What is the function of sesmoid bone? Where is sesmoid bone found?

Answer 296

Serves to protect the tendon Patella (kneecap)- which lies in the patella/quadriceps tendon

Question 297

What is an osteoid matrix?

Answer 297

Part of the ECM of bone which consists of the ORGANIC substances (collagen and non collagenous proteins)

Question 298

What is a ligament?

Answer 298

Fibrous connective tissue that connects bones to other bones

Question 299

What is a tendon?

Answer 299

Fibrous connective tissue that connects muscle to bones

Question 300

What is the end of long bone called?

Answer 300

Epiphysis

Question 301

What is the long part of the long bone called?

Answer 301

Diaphysis

Question 302

What is the cone shaped region of long bone called, which changes shape as we grow?

Answer 302

Metaphysis

Question 303

What is needed for calcification if matrix?

Answer 303

Matrix vesicles (alkaline phosphatase and other enzymes)

Question 304

Which enzyme is a clinical marker of bone damage?

Answer 304

Alkaline phosphatase

Question 305

What is the name of the squamous cells on the bone surface waiting to become active?

Answer 305

Inactive osteoblasts

Question 306

What are the cytoplasmic processes of osteocytes?

Answer 306

Communication Metabolic exchange GAP junctions

Question 307

What are the spaces which contain cell bodies (osteocytes) called?

Answer 307

Lacunae

Question 308

What are caniculae?

Answer 308

Extensions of cytoplasm of osteocytes

Question 309

What cells can revert back to osteoblasts?

Answer 309

Osteocytes

Question 310

What are the spaces where osteoclasts are found called?

Answer 310

Resorption bays and canals

Question 311

What are hydroxyapatite crystals called?

Answer 311

Plates along collagen fibres which are surrounded by a hydration shell (fluid bound to crystals of calcium phosphate and calcium carbonate)

Question 312

What is the significance of layered arrangement in compact bone?

Answer 312

Efficiency (transfer of metabolites and waste) | Strength of bone in multiple directions (from alternating angles good for tension and torsion)

Question 313

What type of bone is embryonic and in fracture repair and lacks organisation?

Answer 313

Woven

Question 314

Compared to compact bone, woven bone has ________ mineral content and ________ cell concentration?

Answer 314

Less | Greater

Question 315

What are the two layers of the periosteum?

Answer 315

Outer fibrous layer- dense irregular ct | Inner osetogenic layer- contains osteoprogenitor cells which can differentiate into osteoblast

Question 316

What is the primary microstructure of bone?

Answer 316

Woven/immature bone- first bone to appear in embryonic development and repair; later replaced by mature bone Collagen fibres arranged in random, interwoven fashion More cells and less minerals

Question 317

What is the secondary microstructure of bone?

Answer 317

Compact/ mature bone- compact dense cortical bone- osteons and interstitial lamellae Spongy bone- mesh work of bone plates or trabeculae- spaces filled with marrow

Question 318

What is remodelling? Explain the remodelling process of bone

Answer 318

``` Skeleton is a metabolically active organ that undergoes continuous remodelling throughout life to compensate for changes on forces being placed on it Haversian system (osteon) is remodelled by the bone remodelling unit which has two components: the resorption cavity (cutting cone) and lamellar formation (closing zone) ``` A resorption cavity is formed as osteoclasts enter the Haversian canal and begin resorbing bone. Osteoclastic activity is followed by an invasion by capillaries, osteoprogenitor cells and osteoblasts Once the osteoclastsc activity ceases, the osteoprogenitor cells divide, forming osteoblasts, which lay down osteoid matrix which becomes calcified and thus manufacture lamellae of bone until a new osteon is completed.

Question 319

What is the purpose of remodelling?

Answer 319

Serves to adjust bone architecture to meet changing mechanical needs Helps repair micro damages in bone matrix preventing the accumulation of old bone Maintains plasma calcium homeostasis

Question 320

How is bone repaired following a fracture?

Answer 320

Haematoma formation- blood escapes from ruptured blood vessels in bone and periosteum and forms a haematoma- bone cells at fracture edge die (no blood supply), phagocytic cells and osteoclasts remove dead and damage tissue, macrophages remove blood clot- inflammation and swelling Fibrocartilaginous callus- new blood vessels infiltrate, pro callus of granulation tissue, fibroblasts produce collagen fibres that span the break, fibroblasts differentiate into chondroblasts which increases hyaline cartilage formation = fibrocartilaginous callus; osteoblasts invade fracture site and begin bone reconstruction Bony callus- new bone trabeculae form by : endochondral ossification (cartilage--> spongy bone) and intramembranous ossification (mesenchymal connective tissue --> spongy bone) Remodelling- bony spongy callus is remodelled into compact bone; bulging material on sides of fractured bone is removed by osteoclast action

Question 321

What is the process of endochondral ossification?

Answer 321

Process of bone formation by which cartilage is replaced by calcified bone matrix--> bone [Endochondral- means within cartilage- so from centre (diaphysis) outwards (to epiphysis)] The cartilage model- in the embryo, chondrocytes lay down hyaline cartilage which is the cartilage model for future bones; as cartilage calcifies, chondrocytes die off Bone collar- osteoblasts, derived from the newly formed periosteum, secrete organic bone matrix (collagen) and matrix undergoes calcification (calcium/phosphate); this results in a bone collar which covers the diaphysis; bone collar is compact bone which thickens over time Primary ossification centre- blood vessels bring osteoblasts to interior and they begin to lay down spongy bone (= primary ossification centre- first centre for bone formation) Medullary cavity and secondary ossification centres- spongy bone of diaphysis centre is absorbed by osteoclasts and cavity created becomes the medullary cavity; shortly after birth secondary ossification sites form in the epiphysis; spongy bone formation persists in the epiphysis; [cartilage remains present at epiphyseal growth plate and articulate cartilage at needs of long bones] Epiphyseal growth plate- band of cartilage (epiphyseal growth plate(0) remains between primary ossification centre and secondary ossification centres- limbs continue to increase in length so long as growth plates are present

Question 322

What is the basic outline of Endochondral ossification?

Answer 322

Hyaline cartilage forms cartilage model for future bones in embryo Chondrocytes in the shaft absorb the surrounding matrix and die, leaving empty lacunae Primitive mesenchymal cells, from the perichondrium, invade the lacunae and differentiate into osteoblasts Osteoblasts form organic bone matrix which becomes calcified to form a sleeve of compact bone around diaphysis Blood vessels from the perichondrium invade the diaphysis (forming primary ossification centre) and bring osteoblasts to centre of diaphysis, so spongy bone forms within diaphysis Spongy bone of diaphysis centre is reabsorbed by osteoclasts forming the medullary cavity (where red and yellow bone marrow is stored); secondary ossification centre form in epiphysis and spongy bone formation persists there Some cartilage remains in the form of epiphyseal growth plates (between epiphysis and diaphysis) and articulating cartilage over the epiphysis (where no perichondrium is present) Epiphyseal growth plate (continual growth) - chondrocytes proliferate and lengthen the bone; they then mature and die to be replaced by osteoblasts which ossify the region

Question 323

What are the two processes of bone formation?

Answer 323

Endochondral ossification | Intramembranous ossification

Question 324

What does Endochondral ossification form?

Answer 324

Long bones of tibia (e.g.)humerus and femur | Forms majority if bones of the body

Question 325

What does intramembranous ossification form?

Answer 325

Flat bones of skull

Question 326

What is the process of intramembranous ossification?

Answer 326

Process of bone formation in which bone forms between sheets of fibrous connective tissue Primitive mesenchymal cells derived from connective tissue cells become osteoblasts located in ossification centres; osteoblasts secrete organic matrix of bone (collagen); calcification occurs when calcium salts are added to the organic matrix- results in the formation of spongy bone trabeculae (containing red bone marrow) Periosteum forms outside the spongy bone, and osteoblasts derived from the periosteum carry out further ossification Trabeculae undergo remodelling to form a compact bone collar which surrounds the inside of spongy bone

Question 327

What is red bone marrow important for?

Answer 327

Red blood cell synthesis

Question 328

What is yellow bone marrow important for?

Answer 328

Contains adipose tissue

Question 329

What is the medullary cavity?

Answer 329

Central cavity of bone shafts where red and yellow bone marrow is stored Lined with endosteum Can be considered to be any area within a long bone that contains bone marrow- so cavity and endosteum is present between trabeculae and in central cavity

Question 330

Which ossification lengthens and thickens long bones?

Answer 330

Endochondral ossification

Question 331

Which ossification mostly thickens flat bone and sometimes long bones?

Answer 331

Intramembranous ossification

Question 332

In Endochondral ossification how does growth in diameter occur?

Answer 332

Deposition of bone at periphery of shaft

Question 333

In Endochondral ossification how does growth in length occur?

Answer 333

At cartilaginous epiphyseal growth plates in orderly series of zones (growth outwards from primary ossification centre)

Question 334

What is osteogenesis imperfecta?

Answer 334

AD Mutations in gene for type I collagen results in abnormal collagen type I synthesis by osteoblasts and fibroblasts--> bone fragility Skeleton and joint fractures, deformities in ears, ligaments, weak teeth, yellow sclerae, inflexible skin, bowing and thinning of bones Less severe cases are not apparent at birth- leads to fragility in bones and multiple fractures of long bones and bone deformities (caused by fracture healing with poor alignment and weak callus)

Question 335

Where is type 1 collagen found?

Answer 335

Major collagen of connective tissue- found in skin, bones and tendons

Question 336

Why does osteogenesis imperfecta have a legal importance?

Answer 336

Possible confusion with multiple fractures caused by deliberate injury and physical abuse

Question 339

What is rickets?

Answer 339

Deficiency of vitamin D in CHILDREN (normally obtained in diet and synthesis in skin by UV action) Low vitamin D means long term serum Ca concentration is low (due to decreased uptake of Ca from gut) which means decreased calcification of osteoid and hence weaker bones Soft bones, malformations, distortion of skull bone, enlargement of costochondral junctions in ribs=rickety rosary

Question 340

What is osteomalacia?

Answer 340

Deficiency of vitamin D in ADULTS (normally obtained in diet and synthesis in skin by UV action) Low vitamin D means long term serum Ca concentration is low (due to decreased uptake of Ca from gut), which means decreased calcification of osteoid and hence weaker bones Trabeculae of bone have an abnormally large amount of non-calcified osteoid covering their trabecular surface- hence weakened by insufficient mineralisation- more prone to fracture FEMORAL NECK, PUBIC RAMUS, SPINE, RIBS More commonly seen in Muslims and elderly

Question 341

What is osteoporosis?

Answer 341

Metabolic bone disease in which mineralised bone is decreased in mass to the point that it no longer provides adequate mechanical support Bone density is reduced to a point where it's a risk of fractures The collagen framework and deposited minerals are broken down much faster than they are formed: -bone resorption> bone formation -osteoclast activity> osteoblast activity Medullary canals in centres of bone become enlarged and gaps develop in lamellae making bone fragile Type 1 post menopausal women- decrease in oestrogen results in increase in osteoclast number Type 2 elderly of both sexes- decreased osteoblast function (so osteoclast function remains the same) Can be treated with bisphosphonate- inhibits osteoclast activity

Question 342

What is achrondroplasia?

Answer 342

Autosomal dominant point mutation in FIBROBLAST GROWTH FACTOR RECEPTOR-3 FGFR-3 causes a gain in function of FGFR-3 gene = failure of proliferation at epiphyseal growth plates= impairs lengthening of long bones This results in a decrease in Endochondral ossification (impairs longitudinal growth of long bones), inhibited proliferation of chondrocytes in epiphyseal growth plate (=thin epiphyseal growth plates and premature fusion of the epiphysis with the diaphysis), decreased cellular hypertrophy, decreased cartilage matrix production Short limb dwarfism (mostly proximal segment), trunk of normal length, vault of skull enlarged, small face, bridge of nose flattened (due to decrease in Endochondral ossification) 80% of the time caused by new mutation Two parents with achondroplasia- 25% homo and die; 50% hetero and achondroplasia; 25% normal

Question 343

What are the risk factors of osteoporosis?

Answer 343

Genetic (peak bone mass is higher in blacks) Insufficient calcium intake (for pmw- 800mg/day) Insufficient calcium absorption and vitamin D (decreased renal activation of vitamin D with age may be a factor in population such as Muslim (cover up) and elderly (stay indoors)) Exercise (immobilisation of bone- bed rest- leads to accelerated bone loss) Cigarette smoking (in women- linked to increase in incidence of op)

Question 344

Explain the importance of vitamin D in normal bone development

Answer 344

Vitamin D is obtained from diet and synthesised in skin by action of UV light Vitamin D undergoes hydroxylation in liver and then in the kidney forming active calcitriol 1,25 dihydroxyvitamin D Calcitriol stimulates absorption of calcium and phosphate by small intestine Therefore high vit D results in a high plasma Ca concentration and so there is increased calcification of osteoid and bones are made stronger (vice versa)

Question 345

What is the effect of growth hormone on bone development before puberty?

Answer 345

Excessive GH = gigantism due to promotion of epiphyseal growth plate activity Insufficient GH = pituitary dwarfism- affects epiphyseal growth plates

Question 346

What is the effect of thyroid hormone on bone development?

Answer 346

Neonatal congenital hypothyroidism- readily reserved by thyroxine administration (T4/T3) If untreated thyroid hormone deficiency can lead to infant with permanent neurological damage (CRETINISM) and other abnormalities like a short stature

Question 347

What is the effect of growth hormone on bone development in an adult?

Answer 347

Excessive GH= cannot cause gigantism- no longer any epiphyseal growth plates; causes increase in bone width ACROMEGALY by promoting periosteum growth

Question 348

What is the effect of sex hormones on bone development?

Answer 348

Influence the development of ossification centres Androgens/oestrogen - give rise to pubertal growth spurt Precocious sexual maturity (brought about by a sex hormone producing tumour) retards bone growth because of premature closure of epiphysis Deficiency- epiphyseal plates may persist into later life, leading to prolonged bone growth and tall stature

Question 349

What are some differences between rickets and osteomalacia?

Answer 349

Rickets- children, soft bones Osteomalacia- adults, increased coating of trabecular bone in non calcified osteoid- weakened bones more prone to fractures

Question 350

What is haemopoiesis?

Answer 350

Formation of blood cells

Question 351

Where does haemopoiesis occur?

Answer 351

``` Bone marrow Spleen Thymus Lymph nodes Lymph follicles Liver ```

Question 352

Outline the process of haemopoiesis

Answer 352

1-Proliferation: starting with a stem cell, the cell divides into 2, one to replace the original stem cell (self renewal) and one that differentiates 2- Early blood cells are held in the bone marrow by adhesion molecules (collagen and fibronectin)- adhesion molecule receptors down regulate during maturation- leading to mature blood cells in circulation 3- Differentiation: haemopoetic progenitor will first differentiate to form either a myeloid blast (RBC, WBC, platelets) or a lymphoid blast (immunoresponse cells); The progenitor cells will differentiate into a certain cell type under the influence of particular cytokines Know flow chart

Question 353

What cytokines result in the formation of rbc's?

Answer 353

Erythropoietin

Question 354

What cytokines result in the formation of lymphocytes?

Answer 354

IL's and TNF's

Question 355

What cytokines result in the formation of platelets/ thrombocytes?

Answer 355

Thrombopoeitin

Question 356

What cytokines result in the formation of granulocytes?

Answer 356

Granulocyte- colony stimulating factor

Question 357

Where are white blood cells formed?

Answer 357

Bone marrow

Question 358

Where do white blood cells often mature?

Answer 358

Thymus or bone marrow or elsewhere

Question 359

Name 5 WBCs that circulate in the blood and lymphatic system

Answer 359

``` Neutrophils Eosinophils Basophils Monocytes Lymphocytes ```

Question 360

Neutrophils

Answer 360

Multi lobed nucleus Granulocyte (pale cytoplasm) FUNCTION Migrate out of circulation to site of infection Phagocytosis Increased production by G-CSF

Question 361

Eosinophils

Answer 361

Bi lobed nucleus Granulocyte (red granules containing phospholipids and enzymes) FUNCTION Migrate to epithelial surfaces (lungs gut skin) Capable of phagocytosis (of antigen antibody complex) Increase in number in allergic reactions Release cytotoxic particles to damage larger particle

Question 362

Basophils

Answer 362

Bi or tri lobed Granulocyte (dark blue granules contain heparin, serotonin and histamine) like MAST cells FUNCTION Migrate to site of damage Mediate acute inflammatory reactions/allergic reactions Histamine= vasodilation and leakage of fluid into tissue Heparin= prevents blood clotting

Question 363

Monocytes

Answer 363

Kidney shaped nucleus NO GRANULES Grey cytoplasm FUNCTION Migrate to become MACROPHAGES in many organs of the body Capable of phagocytosis and interact with T cells Respond to antigenic and inflammatory stimuli

Question 364

Lymphocyte

Answer 364

Deep staining, large round nuclei Small cells Little cytoplasm Nuclear chromatin- stains as light (euchromatin) and dark (heterochromatin) patches FUNCTION B - humoral immunity- stimulated by antigens, transform into plasma cells (when they interact with T cells) or memory cells (when within the lymph nodes), plasma cells secrete immunoglobulins (antibodies) T - mature in thymus gland, express CD4 on surface (helper cells- increase T and B cells and activate macrophages from monocytes), can express CD8 on surface (killer cells- cytotoxic activity inducing apoptosis), permit transformation of B cells into plasma cells

Question 365

Erythrocytes structure

Answer 365

Biconcave disc (facilitates passage through narrow capillaries) Haemoglobin- 4 globulin chains (2 alpha and 2 beta); Each molecule carries a haem Membrane has many glycoproteins- give it shape and specificity 8 micrometer diameter

Question 366

What is the average diameter of a typical human cell?

Answer 366

10-20 micrometers

Question 367

Erythrocytes function

Answer 367

Carries oxygen to tissues and carbon dioxide to lungs

Question 368

Reticular cells structure

Answer 368

Synthesise reticular fibres and surround them with cytoplasm

Question 369

Reticular cell function

Answer 369

Direct the T and B lymphocytes to specific regions within the lymphatic tissues

Question 370

Platelets structure

Answer 370

2-3 micrometer diameter Small round blue particles Produced by megakaryocytes in the bone marrow Complex surface membrane- phospholipid surface for clotting factor and platelet adhesion, via glycoproteins receptors Cytoplasm contains alpha and dense granules Alpha granules contain glycoproteins, fibrinogen and von Willebrand's factor Dense bodies contains serotonin, ADP, catecholamines and Ca2+ for platelet aggregation

Question 371

Describe Red blood cell synthesis (erythropoeisis)

Answer 371

Reduced partial pressure of oxygen is detected in the interstitial peri tubular cells in the kidney This results in an increased production of the erythropoietin hormone which stimulates maturation and release of red cells from bone marrow Haemoglobin increases, partial pressure of oxygen rises and thus EPO production falls

Question 372

Describe the two main pathways by which red blood cells are supplied with energy

Answer 372

2 main metabolic pathways- Emblem Meyerhof pathway (glucose --> lactate and ATP is generated) Hexose monophosphate pathway (G-6-P metabolised and NADPH is generated)

Question 373

What is the survival rate of a rbc?

Answer 373

20 days

Question 374

What is the survival rate for and platelet?

Answer 374

10 days

Question 375

What is the survival rate for WBCs?

Answer 375

1 day- years varies widely

Question 376

What is the minimum diameter of RBCs in capillaries?

Answer 376

3.5 micrometers

Question 377

Platelet aggregation?

Answer 377

Ofhigh we'd

Question 378

What are the three histological forms of muscle?

Answer 378

Skeletal muscle striated Cardiac muscle striated Smooth muscle non striated

Question 379

What is the banding of skeletal muscle?

Answer 379

MHAZI M line is in the H zone which is in the A band (dark) Z line is in the I band (light)

Question 380

What are the main filaments found in muscle?

Answer 380

Actin and myosin (present in all 3 types, only visible in skeletal and cardiac)

Question 381

What filaments are present in the A band?

Answer 381

Actin and myosin, myosin (H zone), actin and myosin

Question 382

What filaments are in the I band?

Answer 382

Actin- backbone along Z line

Question 383

What is the sarcomere?

Answer 383

Distance between adjacent Z lines which are formed by the joining points of actin

Question 384

What is the arrangement of an actin molecule?

Answer 384

Actin filaments are double helical strands of globular protein subunits Can be isolated free in solution from G form (individual globular proteins) - under correct physiological conditions can polymerise into F form (long chain) Tropomyosin, a thinner filamentous polymer, lies in the actin groove Troponin is distributed along the thin filaments attached to tropomyosin at 40nm intervals Each troponin is a Ca2+ receptor Together, troponin and tropomyosin control the interaction of actin and myosin

Question 385

What is the arrangement of a myosin filament?

Answer 385

>150nm long and 10nm thick Light meromyosin tail and heavy meromyosin globular head Heavy meromyosin has the ability to bind actin and split ATP (forming bridges between thick and thin filaments)

Question 386

What is the structure of a Myofibril?

Answer 386

Made up of smaller units- myofilaments (thin actin and thick myosin) Present in a 2a:1m ratio 1000 myofilaments per Myofibril

Question 387

What muscles are voluntary?

Answer 387

Skeletal

Question 388

What muscles are involuntary?

Answer 388

Cardiac and smooth

Question 389

What are two functions of muscle?

Answer 389

Contractility and conductivity

Question 390

Describe the sliding filament mechanism ****

Answer 390

When a muscle is innervated, an influx of Na and outflux of K causes a depolarisation of muscle cytosol which spreads to the T tubules This causes the voltage sensor proteins of the T tubule membrane to change their conformation affecting the associated sarcoplasmic reticulum Ca2+ is released from the sarcoplasmic reticulum from adjacent terminal cisternae Ca2+ binds to the troponin c sub unit of troponin, which results in a conformational change which moves tropomyosin away from the actin binding sites This displacement allows myosin heads to bind to actin and contraction begins: -ATP attached to myosin head is hydrolysed, allowing the myosin head to move to approximate the active site of the actin molecule. ADP and Pi remain attached to the myosin head - Pi is released from the myosin head, in the presence of calcium, causing the myosin head to bind with the actin filament -ADP molecule is released from the myosin head, causing the myosin head to alter its conformation, moving the actin filament towards the centre of the sarcomere (POWER STROKE) -A new ATP molecule attaches to the globular head of the myosin causing it to detach from that active site of the actin molecule and to return to its normal position - Cycle repeats itself 200-300 times for complete contraction of the sarcomere- myosin binds to another active site further along the actin filament

Question 391

Describe the mechanism of innervation of muscle and excitation contraction coupling

Answer 391

Arrival of ap at presynaptic neuron terminal causes an influx of Ca2+ ions from ECF to ICF Influx of Ca2+ ions causes acetyl choline (ACh) containing vesicles to migrate to the neurons membrane, bind and release ACh into the synaptic cleft ACh diffuses across the synaptic cleft and binds to nicotinic ACh receptors bound to the motor end plate Receptors are ligand gated ion channels and when they bind ACh the channels open allowing an influx of Na and out flux of K to and from the muscle cytosol= depolarisation of the sarcomere Depolarisation spreads to t tubules, voltage sensor proteins of the t tubule membrane change their conformation which affects the associated sarcoplasmic reticulum Ca2+ is released from adjacent terminal cisternae ca2+ binds to troponin c subunit of troponin Contraction cycle is initiated and Ca2+ is returned to the terminal cisternae of the sarcoplasmic reticulum

Question 392

What happens to the banding when contraction occurs?

Answer 392

H zone and I band shorten Sarcomere shortens A band is unaffected

Question 393

What is the clinical importance of troponin c?

Answer 393

In cardiac muscle act as a marker for cardiac ischaemia Released from heart muscle within an hour Measured from 1 - 20 hours Smallest change in troponin c is indicative of damage (not proportional)

Question 394

What is rigor mortis?

Answer 394

In death when no ATP is being formed, no ATP is available to bind to myosin filaments, causing them to detach from the actin filament. As a result myosin remains bound to actin and muscle remains contracted = hardness of death

Question 395

What is the structure of an entire organ of skeletal muscle?

Answer 395

Muscle= bundle of fascicles Fascicles = bundle of fibres Fibre= bundle of myofibrils Myofibril- bundles of myofilaments (actin and myosin) Epimysium- surrounds entire muscle Perimysium- surrounds individual muscle fascicles Endomysium- surrounds individual muscle fibres

Question 396

Explain the muscle continuity of (skeletal) muscle fibres, muscle sheath, tendon and bone

Answer 396

Uegcyugecwyegcuygc Skeletal muscle fibres connect with tendon collagen bundles at myotendinous junctions Sarcolemma always lies between collagen bundles and muscle fibre myofilaments Epimysium, perimysium and endomysium (bearing capillaries and nerves) become connective tissue joining the muscle to the tendon to the bone

Question 397

What will the transverse section of the I band look like?

Answer 397

Thin dots = ony actin present

Question 398

What does the transverse section of the h band look like?

Answer 398

Thick dots= only myosin present

Question 399

What does a transverse section of the M line look like?

Answer 399

Thick dots with lines joining all dots

Question 400

What does a transverse section of the A band look like?

Answer 400

Thick and thin dots = overlap of actin and myosin

Question 401

What are t tubules and how are they associated with sarcoplasmic reticulum in a) skeletal muscle, b) cardiac muscle and c) smooth muscle?

Answer 401

T(ransverse) tubules are deep invaginations of the sacrolemma (plasma membrane) of the muscle Run perpendicular to myofilaments a) In skeletal muscle- T tubules located at junction overlap between A and I bands; present with a pair of terminal cisternae (bulbous large areas of sarcoplasmic reticulum) = triad b) In cardiac muscle- T tubules located at Z line; present with a single terminal cisterna = diad c) In smooth muscle- t tubules are not present

Question 402

Where do t tubules interact with the myofilaments in a) skeletal muscle and b) cardiac muscle?

Answer 402

a) skeletal muscle - junction overlap between A and I bands | b) cardiac muscle - Z line

Question 403

What are some key structural features of skeletal muscle?

Answer 403

Striated No branching, parallel myofibrils Distinct myofibrils Multiple peripheral nuclei T tubules in line with junctions between A and I bands T tubules present as a triad with two adjoining terminal cisternae

Question 404

What is the derivation if skeletal muscle?

Answer 404

Mesodermal (paraxial)

Question 405

What is the nature of the repair of skeletal muscle?

Answer 405

Cells cannot divide but tissues can regenerate by mitotic activity of satellite cells so that hyperplasia (increase in cell number) follows muscle injury Satellite cells can also fuse with existing skeletal muscle sells to increase mass (skeletal muscle hypertrophy- swelling) Gross damage is repaired by connective tissue which leaves a scar If the nerve or blood supply is interrupted muscle fibres degenerate and are replaced by fibrous tissue

Question 406

What two types of skeletal muscle are there?

Answer 406

``` Red- Low intensity high endurance exercise Smaller rich in myoglobin, vascularisation and oxidative enzymes Poor in ATPase Numerous mitochondria Fewer neuromuscular junctions Slow, repetitive and weaker contraction Slowly fatigue = limb muscle of animals, postural muscles of back, breast muscle of migrating birds ``` ``` White- High intensity low endurance exercise Larger Poor in myoglobin, vascularisation and oxidative enzymes Rich in ATPase Fewer mitochondria More neuromuscular junctions Faster, stronger contraction Rapidly fatigue = extra ocular muscles, muscles controlling fingers, breast muscle of domestic hens ```

Question 407

What are some key structural features of cardiac muscle?

Answer 407

Striated Branching, unparallel myofibrils Indistinct myofibrils 1 or 2 central nuclei T tubules in line with junctions between Z lines T tubules present as a diad with a single adjoining terminal cisternae

Question 408

What is the derivation of cardiac muscle?

Answer 408

Mesodermal (paraxial)

Question 409

What is the nature of repair of cardiac muscle?

Answer 409

Incapable of regeneration | Following damage fibroblasts invade, divide and lay down scar tissue

Question 410

What are extrinsic muscles?

Answer 410

Skeletal muscle attached to bones and cartilage- allows change in POSITION (of e.g. Tongue)

Question 411

What are intrinsic muscles?

Answer 411

Skeletal muscle not attached to bone- allows a change in SHAPE (of e.g. Tongue)

Question 412

What initiates contraction to occur in the heart?

Answer 412

Action potential is generated in the SAN, passed to the AVN and from there they are carried by specialised myocardial cells (bundle of His), of which the distal conducting cells are the PURKINJE FIBRES, to the ventricular muscle- causing simultaneous contraction of the ventricles

Question 413

What are the PURKINJE fibres?

Answer 413

``` Distal conducting myocardial cells at the base of the ventricles Large cells with: Abundant glycogen Sparse myofilaments Extensive gap junction sites ```

Question 414

Why are PURKINJE fibres used for ventricular contraction instead of cardiac fibres?

Answer 414

PURKINJE fibres conduct ap's more rapidly at 3-4m/s compared to 0.5m/s for cardiac fibres This rapid conduction enables ventricles to contract in a synchronous manner

Question 415

What are some key structural features of smooth muscle?

Answer 415

Spindle shaped fusiform cells with a central nucleus Not striated (no sarcomere) No T tubules Actin and myosin filaments arranged diagonally within the cell, spiralling down the long axis so the smooth muscle contracts in a twisting way

Question 416

What is the derivation of smooth muscle?

Answer 416

Mesoderm/ ectoderm (paraxial)

Question 417

What is the nature of repair of the smooth muscle?

Answer 417

Cells retain their mitotic activity and can form new smooth muscle cells Ability is particularly evident in pregnant uterus where muscle wall becomes thicker by hypertrophy (swelling) and by hyperplasia (mitotis) of individual cells

Question 418

What types of smooth muscle are there?

Answer 418

Circular - appears fusiform/ spindle shaped in transverse cut; inner wall of muscularis externa in gut Longitudinal- appears circular in transverse cut; outer wall of muscularis externa in gut

Question 419

What is the arrangement of actin and myosin in smooth muscle?

Answer 419

Arranged diagonally within the cell | Form sheets bundles or layers containing thousands of cells

Question 420

What is the arrangement of actin and myosin in skeletal muscle?

Answer 420

A and I bands

Question 421

What is the arrangement of actin and myosin in cardiac muscle?

Answer 421

A and I bands

Question 422

What initiates smooth muscle cell contraction?

Answer 422

Responds to stimuli in the form of nerve signals, hormones, drugs, or local concentrations of blood gases

Question 423

Wha are two types of modified smooth muscle cells?

Answer 423

Myoepithelial cells- form a basketwork around exocrine glands (sweat,salivary and mammary); contraction assists with secretion Myofibroblasts- at sites of wound healing; produce collagenous matrix but also contract

Question 424

Describe the remodelling process of muscle?

Answer 424

Change in number of proteins ; replacement of contractile proteins occurs in 2 weeks Continuous

Question 425

What is atrophy?

Answer 425

When destruction of protein > replacement of protein Muscle wasting Loss of protein (actin and myosin) causes fibre diameter to decrease (number of fibres remains the same)

Question 426

What is hypertrophy?

Answer 426

When destruction of protein < replacement of protein Muscle increases in size Gain of proteins (actin and myosin) causes fibre diameter to increase (number of fibres remains the same)

Question 427

What are some causes of atrophy?

Answer 427

Disuse- muscle fibres shrink when there is not frequent movement against resistance Age- muscle fibres shrink after the age of 30 (50% loss by 80) Denervation- muscle fibre shrinks as it no longer receives contractile signals that are required to maintain the normal size (causes weakness, flaccidity, twitching) ; muscle fibres are replaced with fibrous and fatty tissue

Question 428

What is myasthenia gravis?

Answer 428

Autoimmune destruction of end plate ACh receptors so ACh cannot bind and is continuously broken down by acetylcholinesterase Loss of junctions, folds at end plate Widening of synaptic cleft CRISIS when it affects respiratory muscles Symptoms- fatigability, sudden falling due to reduced ACh release; drooping eyelids; double vision, effected by general state of health and emotion Treatment- acetylcholinesterase inhibitors (neostigimine, physostigimine; placing ice on eyelids decreasing acetylcholinesterase activity

Question 429

What is botulism?

Answer 429

Toxins block ACh release | Botox cosmetic treatment- removes wrinkles

Question 430

What was botulin previously used for?

Answer 430

Originally used as a medicine to stop twitching in the eyes

Question 431

What is duchenne muscular dystrophy?

Answer 431

Complete absence of dystrophin Consequences of protein abnormality: - muscle fibres tear themselves apart on contraction -Enzyme creatine (phospho) kinase liberated into serum -Calcium enters cell causing death of cell -Pseudohypertrophy (swelling) before fat and connective tissue replaces muscle fibres Symptoms- gowers sign (crouching to get up); contractures (imbalance between agonist and antagonist muscles)

Question 432

What is organophosphate poisoning?

Answer 432

Irreversibly inhibits acetyl cholinesterase | So ACh remains in the receptors and muscle stays contracted

Question 433

What is malignant hyperthermia?

Answer 433

Rare AD disorder Life threatening reaction to certain drugs (volatile anaesthetic agents and neuromuscular blocking agent succinylcholine) used for general anaesthesia Succinylcholine inhibits action of ACh acting non competitively on nicotinic receptors Succinylcholine is degraded by butyrylcholinesterase much more slowly than the degradation of ACh by acetylcholinesterase In susceptible individual these drugs can induce a drastic and uncontrolled increase in skeletal muscle oxidative metabolism, quickly overwhelming the body's capacity to supply oxygen and remove carbon dioxide and thus regulate body metabolism Eventually leads to circulatory collapse and death if not quickly treated Malignant hyperthermia us treated by the correction of hyperthermia, acidosis, dysfunction, discontinuation if triggering agents and administration of DANTROLENE DANTROLENE is a muscle relaxant which works by preventing the release of calcium

Question 434

What does the CNS consist of?

Answer 434

The brain and the spinal cord

Question 435

What are the membranous coverings of the brain and spinal cord in the CNS?

Answer 435

``` MENINGES Skull/ spinal vertebrae Dura mater Arachnoid mater Pia mater Brain / spinal cord ``` (Outside inwards)

Question 436

What are collectively known as the leptomeninges?

Answer 436

Arachnoid mater and pia mater

Question 437

What is the space between The arachnoid and pia mater known as?

Answer 437

Sub arachnoid space

Question 438

What does the sub arachnoid space consist of?

Answer 438

Highly vascularised plane | Contains cerebrospinal fluid

Question 439

How does the sub arachnoid space form?

Answer 439

By the failure of the arachnoid mater to follow the furrows of the brain By the failure of the arachnoid mater to adhere to the pia mater (as a result of the dilated blood vessels of the brain)

Question 440

What is the function of CSF?

Answer 440

Major fluid of brain Supplies nutrients and oxygen to CNS neurones Carries away metabolites of CNS Exerts hydrostatic pressure= CNS pressure

Question 441

What is the effect of having too much CSF?

Answer 441

Clinical implications- intracranial hypertension

Question 442

What is the equivalent fluid to CSF in the PNS?

Answer 442

Endoneurial fluid- surround the individual nerve fibres

Question 443

What epithelia are found on the meninges?

Answer 443

Stratified squamous

Question 444

Wich layer of the meninges forms the boundary between the PNS and CNS?

Answer 444

Pia mater

Question 445

How are neurones arranged in the spinal cord (CNS)?

Answer 445

``` Grey matter (collection of cell bodies) White matter (collection of nerve fibres) ``` Butterfly shaped grey matter surrounded by white matter Smaller wings = dorsal (where afferent sensory neurones enter) Larger wings = ventral (where efferent motor neurones leave)

Question 446

How are neurones arranged in the brain (CNS)?

Answer 446

``` Grey matter (collection of cell bodies) White matter (collection of nerve fibres) ``` Secondary migration of grey matter has occurred resulting in the grey matter (cerebrum and cerebellum) forming a convoluted outer layer = cortex Grey matter can also exist as deeply placed collections of cell bodies= nuclei White matter is present as fibre tracts

Question 447

What gives white matter its white appearance?

Answer 447

Presence of lots of myelin (on nerve fibres)

Question 448

What cells are found surrounding all axons of the CNS?

Answer 448

Oligodendrocytes

Question 449

How do oligodendrocytes form myelin sheath around axons in the CNS?

Answer 449

Oligodendrocytes wind themselves around the axon, wrapping it in concentric layers of its own plasma membrane (myelin) 250 axons per oligodendrocyte cell

Question 450

How many pairs of cranial nerves are there?

Answer 450

12 (10 of which are present in the PNS as 1st and 2nd cranial nerves are actually part of the CNS)

Question 451

How many pairs of spinal nerves are there?

Answer 451

31 (all in PNS)

Question 452

What does the PNS consist of?

Answer 452

All the afferent (sensory) and efferent (motor) (to the CNS) nerves

Question 453

What are the membranous connective tissue coverings of the nerves in the PNS?

Answer 453

Epineurium- surrounds entire nerve (bundle of nerve fascicles) Perineurium- surrounds nerve fascicles (bundle of nerve fibres) Endoneurium- surrounds individual nerve fibres (one axon)

Question 454

What is the function of the connective tissue sheaths that surround nerves?

Answer 454

Blood- supply nutrients and oxygen, and remove metabolites of PNS

Question 455

What is the structure of a sensory neurone?

Answer 455

Pseudo unipolar | Myelinated

Question 456

Where do sensory neurones enter the spinal cord?

Answer 456

Dorsal root

Question 457

What is the structure of a motor neurone?

Answer 457

Multipolar | Somatic- myelinated and autonomic- unmyelinated

Question 458

How do motor neurones leave the spinal cord?

Answer 458

Ventral root

Question 459

What is the structure of inter neurones?

Answer 459

Multipolar Smallest neurones Held solely within brain and spinal cord substance

Question 460

What is the structure of the cerebrospinal ganglia of the sensory neurones in the PNS?

Answer 460

Round large ovoid nuclei Conspicuous nucleoli Each ganglia cell is surrounded by a single layer of satellite support cells Cell bodies are grouped at the periphery of the ganglia Myelinated fibres grouped in middle of ganglia

Question 463

What are ganglia and where are they found?

Answer 463

Ganglia are collections of cell bodies surrounded by connective tissue capsules Found in PNS There are two types- sensory (cerebrospinal) ganglia (fusiform swellings of each dorsal root of spinal nerves) and motor autonomic ganglia (found in two parallel chains (sympathetic chain of ganglia), along anterior surface of vertebrae OR as poorly encapsulated structures near or within the target organs (parasympathetic ganglia) There is no such thing as motor somatic ganglia as motor somatic neurones consist of only one axon (with no ganglia)

Question 465

What is the structure of the autonomic ganglia found in the motor neurones of the PNS?

Answer 465

``` No peripheral arrangement of cell bodies Small ganglion cells Unmyelinated axons Ill defined layer of satellite cells Eccentric cell body nuclei ```

Question 468

What is the general structure of a neurone in the CNS and PNS?

Answer 468

Dendrites- receive stimuli from sensory organs or other neurones (from the environment) and conduct nerve impulse towards cell body; specialisations of cell body Cell body- involved in maintenance of cell; has a light nucleus, darker nucleoli, Nissl substance (aggregation of RER-involved in protein synthesis and is basophilic due to high conc of rRNA) Axon- exists as a single process; conducts nerve impulses always from cell body to other neurones or target organs

Question 469

What is the neurone, nerve cell and nerve fibre?

Answer 469

Neurone is collectively the dendrites, cell body and axon Nerve cell is sometimes used to refer to cell bodies and attached dendrites, or can be interchanged with the use of neurones Nerve fibres refers to the axons

Question 470

What are the three basic neurone types?

Answer 470

Multipolar- multiple dendrites and 1 axon (many processes) Bipolar- 1 dendrite and 1 axon (2 processes) Pseudo unipolar- 1 axon (fusion of dendrite and axon) (1 process)

Question 471

Where are multipolar neurones found?

Answer 471

Motor neurones

Question 472

Where are bipolar neurones found?

Answer 472

Largely in the retina of the eye

Question 473

Where are pseudo unipolar neurones found?

Answer 473

Sensory neurones

Question 474

What is myelin sheath?

Answer 474

Where Schwann cells or oligodendrocyte cells wrap their membrane (containing myelin) in concentric layers around the axon At regular intervals along the axon

Question 475

What is a node of Ranvier?

Answer 475

The gaps between the discontinuous myelin sheath along an axon

Question 476

What is the initial segment of a myelinated neurone?

Answer 476

The initial node of Ranvier before the first myelin sheath

Question 477

What is the internodal membrane of a myelinated axon?

Answer 477

Region of axon underneath the myelin sheath

Question 478

What is the relevance of a high lipid content of the myelin sheath?

Answer 478

Cannot conduct electricity resulting in saltatory conduction | Dissolved by xylene and alcohol in tissue processing

Question 479

What is saltatory conduction?

Answer 479

Propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials without the need to increase the diameter of the axon

Question 480

How is the speed of an action potential along an axon increased?

Answer 480

Myelinated axons- presence of myelination= quicker transmission Schwann cells wrap around the axons, insulating them and their lipid content means they can't conduct electricity; electricity can nkt be conducted at nodes of ranvier; so action potential jumps from node of Ranvier to the next in saltatory conduction Diameter of axon- larger the axon diameter= quicker transmission Temperature

Question 481

Describe the structure of the cell body

Answer 481

Light nucleus, dark nucleolus Golgi apparatus- packages neurotransmitters into vesicles Nissl substance- RER aggregates- where protein synthesis occurs; basophilic due to high rRNA content Dendrites Dendrite spines- associated with learning experience (more you learn the more dendritic spines you have) Cell membrane- bilipid layer; separates inside from outside, selectively permeable to certain ions (ionic conc grad across cm/ ions are charged/ electrochemical gradient across cm; neurone is electrically charged) Ion channels in cell membrane- membranes have many pores which form ion channels for specific ions; voltage gated channels opens and close by changes in voltage across the membrane; other channels open and close in response to neurotransmitters/ ligands Axon (axial hillock and axon terminal)

Question 482

Describe the axon

Answer 482

Summaries all the input Initiates the all or nothing action potential Conducts ap's away from cell bodies towards terminals Depolarisation of terminal leads to secretion of neurotransmitter Communicates with follower cells Varies in thickness and length Can be myelinated or unmyelinated May divide into twig like branches (terminal arborations) at terminal site of axon, which in turn may have swellings known as boutons terminaux (synaptic knob)

Question 483

What is the relevance of multiple sclerosis and demyelination?

Answer 483

Nerve impulse has to travel further due to demyelination as saltatory conduction is inhibited; therefore the response is much slower Myelin sheath (oligodendrocytes and schwann cells) is destructively removed from the axon and replaced by scar tissue Conduction velocity slows down as saltatory conduction is impaired Scar tissue cannot permit conduction and therefore the axon is useless

Question 484

How much of the CNS and PNS is made up of neurones and how much of glial cells?

Answer 484

10% neurone | 90% glial cells

Question 485

What are glial cells?

Answer 485

Cells that support and insulate neurones in the CNS and PNS

Question 486

What is temporal summation?

Answer 486

Inputs summated with respect to their time of arrival on the cell body/ dendrites - high frequency over short period of time

Question 487

What is spatial summation?

Answer 487

Inputs summated with respect to their relative spatial location n the cell body/ dendrites- lots of input from different sources/ presynaptic knobs

Question 488

How does communication between neurones occur?

Answer 488

Depolarisation leads to secretion of chemical messengers called neurotransmitters

Question 489

What are excitatory neurones and what do they release?

Answer 489

Excitatory neurones (causes its follower cell to be depolarised) release glutamate / aspartate neurotransmitter

Question 490

What are inhibitory neurones?

Answer 490

``` Inhibitory neurones (causes its follower cell to be hyper polarised) Release glycine/ GABA (gamma amino butyric acid) ```

Question 491

What is the motor neurone system made up of?

Answer 491

Somatic (voluntary) and autonomic (involuntary) nervous systems

Question 492

What is grey matter?

Answer 492

Collection of cell bodies (nerve cells)

Question 493

What is white matter?

Answer 493

Collection of neuronal axons (nerve fibres)

Question 494

How is the somatic system arranged?

Answer 494

Consists of 1 neurone carrying the output from the CNS The neurone terminates directly on the effector organ (SKELETAL MUSCLE) The efferents are underdeveloped at birth and fully developed at puberty

Question 495

What are the effector organs for the somatic nervous system?

Answer 495

Skeletal muscle

Question 496

How is the autonomic nervous system arranged?

Answer 496

Pathways consists of 2 neurones 1 neurone (pre-ganglionic) has cell body in CNS and 1 neurone (post-ganglionic) has cell body in PNS Cell body in PNS is either in the sympathetic chain (ganglions) or near the effector organ (parasympathetic ganglion)

Question 497

What are the effector organs of the autonomic nervous system?

Answer 497

Cardiac muscle Smooth muscle Secretory glands

Question 498

What are the functions of the autonomic nervous system?

Answer 498

Part of peripheral nervous system that regulates the functions of our internal viscera/organs Maintains homeostasis Becomes active along with organogenesis Promotes excretory mechanisms

Question 499

What does the autonomic nervous system consist of?

Answer 499

Sympathetic and parasympathetic nervous system

Question 500

What is the sympathetic nervous system involved in?

Answer 500

Stimulating effector organs | Fight or flight response

Question 501

What is the parasympathetic nervous system involved in?

Answer 501

Inhibiting effector organs | Relaxation- rest or digest

Question 502

Describe the pathway by which the sympathetic nervous system distributes its fibres to the effector organ

Answer 502

Thoraco lumbar outflow (nerve fibres have cell bodies in all 12 thoracic sections and first 2 lumbar sections) Short pre-ganglionic neurone Sympathetic chain- may synapse at: (1) same level of origin (paravertebral origin); (2) different level of origin (up or down sympathetic chain); (3) nowhere in sympathetic chain Long post-ganglionic neurone

Question 503

Describe the pathway by which the parasympathetic nervous system distributes its fibres to the effector organ

Answer 503

Cranial sacro outflow (nerve fibres have cell bodies in oculomotor, facial, glossopharangeal, vagus cranial section and S2,3,4 of the sacral section) Long pre-ganglionic neurone Short post-ganglionic neurone

Question 504

What synapses and receptors are present in the sympathetic nervous system?

Answer 504

Sympathetic Pre-ganglionic neurone are cholinergic Post ganglionic neurones express nicotinic receptors and are noradrenergic Effector muscle expresses alpha and beta adrenoreceptors

Question 505

What synapses and receptors are present in the sympathetic nervous system?

Answer 505

Parasympathetic Pre-ganglionic neurone are cholinergic Post ganglionic neurones express nicotinic receptors and are cholinergic Effector muscle expresses muscarinic receptors

Question 506

What are some of the functions of the sympathetic nervous system?

Answer 506

``` Fight/flight/ fright response Diversion of blood to muscles and heart Increase in heart rate Increase in blood pressure Reduced blood flow to GIT and skin Hyperventilation ```

Question 507

What are some of the functions of the parasympathetic nervous system?

Answer 507

Relaxation Reduced heart rate a d force of contraction Promotes digestion Promotes bodily functions such as bladder emptying Promotes sleep

Question 508

What are the 6 main glial cells and their functions?

Answer 508

Astrocytes- assist in transfer of nutrients and waste across the blood brain barrier (CNS) Oligodendrocytes- myelination up to 250 axons/cell (CNS) Microglia- immune and inflammatory functions (CNS and PNS) Ependyma- line ventricles and central canal of spinal for circulation of CSF) (CNS) Schwann cell- myelination 1 axon/ cell (PNS) Satellite- physical support of peripheral neurones (afferent and efferent) and ganglia (PNS)

Question 509

What cells are found surrounding all axons of the PNS?

Answer 509

Schwann cells

Question 510

How do Schwann cells form myelin sheath around axons in the PNS?

Answer 510

Schwann cells wind themselves around the axon, wrapping it in concentric layers of its own plasma membrane (myelin) 1 axons per schwann cell

Question 511

Why is it normally difficult to see myelin sheath under a microscope?

Answer 511

Myelin membrane of Schwann/oligodendrocyte cells which wraps itself around the axon contains lipid (being a membrane) which is dissolved by lipid solvents such as xylene and alcohol in the tissue processing. Hence this causes the breakdown of the myelin sheath so it can't be seen under a microscope

Question 512

What fixative can be used to preserve the lipid in myelin sheath

Answer 512

Osmium tetraoxide - so myelin sheath stains an intense black

Question 513

What is the pathology of muscular dystrophy?

Answer 513

Genetic faults causes the absence or reduced synthesis of specific proteins which anchor the actin filaments to the sarcolemma (membrane) such that in their absence the muscle fibre cells may tear themselves apart when contracting

Question 514

What is Barrett oesophagus?

Answer 514

Stratified squamous --> simple columnar in oesophagus as a result of acid reflux from the stomach

Question 515

What type of gland is intestinal gland?

Answer 515

Simple tubular

Question 516

What type of gland is the merocrine sweat gland?

Answer 516

Simple coiled tubular

Question 517

What type of gland is the sebaceous gland?

Answer 517

Simple branched acinar

Question 518

What type of gland are the gastric glands, mucous glands of oesophagus, tongue and duodenum?

Answer 518

Simple branched tubular

Question 519

What type of glands are the mammary glands?

Answer 519

Compound acinar

Question 520

What type of glands are the mucous glands?

Answer 520

Compound tubular

Question 521

What type of glands are the salivary glands?

Answer 521

Compound tubuloacinar

Question 522

What is the function of the gall bladder?

Answer 522

To extract water and electrolytes from bile produced by liver, thus reducing its volume

Question 523

What is the function of the parotid salivary gland?

Answer 523

Removes sodium ions rendering saliva hypotonic

Question 524

Describe the epididymis

Answer 524

Pseudostratified epithelium StereoCiliated Principal cells- (ecs) absorb fluid, secrete substances which promotes sperm maturation, phagocytose residual bodies and degenerate sperm Basal cells- (beneath ecs)- stem cells of epithelia