ToB

Question 1

State the relationship between

• meters
• millimetres
• micrometres
• nanometres
• angstroms

Answer 1

Metre = m

Millimetre = 10 to the -3 m

Micrometre = 10 to the -6 m

Nanometre = 10 to the -9 m

Angstrom = 10 to the -10 m

Question 2

State the meaning of the term tissue.

Answer 2

A collection of cells specialised to perform a particular function.

Question 3

What to aggregations of tissues constitute?

Answer 3

Organs.

Question 4

Define histology.

Answer 4

The study of the structure of tissues by means of special staining techniques combined with light and electron microscopy.

Question 5

Why is histology valuable in diagnosis?

Answer 5

In many diseases such as Crohn’s, treatment is not given until the histopathologists have given a diagnosis. A biopsy and histology is the final proof for many diseases, like lung/breast cancer.

Question 6

Define the term biopsy.

Answer 6

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

Question 7

Describe a smear and give an example of a tissue that can be sampled by this method.

Answer 7

Collecting cells by spontaneous/ mechanical exfoliation, and smear on the slide.

Example tissue: cervix, buccal cavity.

Question 8

Describe a curettage and give an example of a tissue that can be sampled by this method.

Answer 8

Removal of tissue by scooping/ scraping.

Example of tissue: endometrial lining of the uterus.

Question 9

Describe a needle biopsy and give an example of a tissue that can be sampled by this method.

Answer 9

Put needle into tissue to gather cells.

Example of tissues: brain, breast, liver, kidney, muscle.

Question 10

Describe a direct incision biopsy and give an example of a tissue that can be sampled by this method.

Answer 10

Cut directly into the tissue of interest and remove the tissue.

Example of tissue: skin, mouth, larynx.

Question 11

Describe an endoscopic biopsy and give an example of a tissue that can be sampled by this method.

Answer 11

Removal of tissue via instruments through an endoscope.

Example of tissue: lung, intestine, bladder.

Question 12

Why does tissue in a slide need to be fixed?

What does it do the proteins?

Answer 12

To confer stability; unfixed tissues are subject to putrefaction and attack by autolytic enzymes.

It makes proteins insoluble. Macromolecular cross linkage.

Question 13

Name two common fixatives.

Answer 13

Formaldehyde and glutaraldehyde.

Question 14

Describe how tissue processing can lead to the formation shrinkage artefacts.

Answer 14

During slide preparation the tissue is dehydrated then rehydrated, which can lead to abnormalities in the final slide.

Question 15

Describe the 5 steps of tissue preparation for microscopy.

Answer 15

1. FIXATION: add formaldehyde/glutaraldehyde, cross linking adjacent proteins, arresting biological activity.
2. DEHYDRATION AND CLEARING: Ethyl alcohol replaces water, cleared with xylene/toluene to make miscible with wax.
3. WAX EMBEDDING: wax impregnation at 56C, solidifies so it can be sectioned.
4. STAINING: xylene clears wax, hydrated with descending % of alcohol, as most stains are water soluble. Dyes selectively stain components based on chemical nature.
5. MOUNTING: Slides are dehydrated, placed in xylene, mounted on xylene based medium, coverslip placed on top.

Question 16

What does H&E stand for?

Answer 16

Haemotoxylin and Eosin

Question 17

What does PAS stand for?

Answer 17

Periodic Acid-Schiff

Question 18

What does haemotoxylin stain in cells, and what colour does it stain them?

Answer 18

It stains ACIDIC compoonents of cells, PURPLE/BLUE.

• Nucleolus (RNA)
• Chromatin (DNA)

Question 19

What does eosin stain in cells, and what colour does it stain them?

Answer 19

It stains BASIC components of cells, PINK.

• Most cytoplasmic proteins
• Extracellular fibres

Question 20

What does Periodic Acid-Schiff stain, and what colour does it stain them?

Answer 20

It stains CARBOHYDRATES and GLYCOPROTEINS.

MAGENTA

Question 21

What is PHASE CONTRAST microscopy?

Advantages?

Answer 21

Using the interference effects of two combining light waves.

Advantage: It enhances the image of unstained cells.

Question 22

What is DARK FIELD microscopy?

Advantages?

Answer 22

Exclude unscattered beam (light/electron) from the image.

Advantages: can use live and unstained samples.

Question 23

What is FLUORESCENCE microscopy?

Advantages?

Answer 23

Targets molecule of interest with fluorescence.

Advantage: can use multiple fluorescent stains on one specimen.

Question 24

What is CONFOCAL microscopy?

Advantages?

Answer 24

Tissue labelles with one or more fluorescent probes.

Advantage: Eliminates ‘out of focus flare’, 3D imaging from a series of 2D images, imaging of living specimens.

Question 25

Define epithelia

Answer 25

Sheets of continguous cells, of varied embryonic origin, that cover the external surface of the body and line internal surfaces.

Question 26

2 examples of an exterior surface with an epithelial lining. Which germ layer do they come from?

Answer 26

Skin Cornea of eye ECTODERM

Question 27

3 examples of interior surfaces opening to the exterior that have epithelial linings. Which germ layer do they come from?

Answer 27

Gastrointestinal tract. ENDODERM Respiratory tract. ENDODERM Genitourinary tract. MESODERM

Question 28

5 examples of interior spaces not opening to the exterior which have epithelial linings. Which germ layer do they come from?

Answer 28

Pericardial sac Pleural sac Peritoneum Blood vessels Lymphatic vessels All come from the MESODERM

Question 29

What are the two main ways of classifying epithelium? (explain both)

Answer 29

SIMPLE: one cell layer thick STRATIFIED: more than one cell layer thick

Question 30

What are the 4 types of simple epithelia?

Answer 30

Squamous Cuboidal Columnar Pseudostratified

Question 31

What are the 5 types of stratified epithelia?

Answer 31

Squamous - keratinised Squamous - non keratinised Cuboidal Columnar Transitional

Question 32

Name some locations and functions of simple squamous epithelia.

Answer 32

Locations: blood vessel lining (ENDOTHELIUM), lining of body cavities (MESOTHELIUM, pericardium, pleura, peritoneum), alveoli, Bowman's capsule, Loop of Henle. inner and middle ear. Functions: lubrication (viscera), gas exchange, barrier (Bowman's), active transport via pinocytosis (meso/endothelium).

Question 33

Name some locations and functions of simple cuboidal epithelium.

Answer 33

Locations: Glands (thyroid follicles, small ducts of many exocrine glands), kidney tubules, germinal epithelium surface of ovary. Functions: absorption and conduit (exocrine glands), absorption and secretion (kidney tubules), barrier/covering (ovary), hormone synthesis, storage and mobilisation (thyroid).

Question 34

Name some locations and functions of simple columnar epithelium. What feature might it have on its apical surface?

Answer 34

Locations: stomach lining and gastric pits, small intestine and colon, gallbladder, large ducts of some exocrine glands, uterus, oviducts, ductuli efferents of testis (epididymis) Functions: absorption, secretion, lubrication, transport. MICROVILLI

Question 35

What is a zona occludens?

Answer 35

A tight junction

Question 36

What does occludin do?

Answer 36

Binds adjacent plasma membranes together tightly, so membrane proteins can not bypass and are restricted to the apical surface, and segregate others to the lateral and basal surfaces.

Question 37

Name some locations and functions of simple pseudostratified epithelia. What other features might they have?

Answer 37

Locations: URT (lining of nasal cavity, trachea and bronchi), epididymis and ductus deferens, auditory tube, tympanic cavity, lacrimal sac, large excretory ducts. Functions: secretion and conduit (URT, ductus deferens), absorption (epididymis), mucus secretion (URT), particle trapping and removal (URT). CILIA, MUCUS SECRETION

Question 38

Name some locations and functions of stratified squamous keratinised epithelium.

Answer 38

Locations: surface of skin, limited distribution in oral cavity. Functions: prevents water loss, protection against abrasion and physical trauma, prevents ingress of microbes, shields against UV light damage.

Question 39

Name some locations and functions of transitional stratified epithelium.

Answer 39

Locations: renal calcyes, ureters, urethra, bladder Functions: distensibility, protection of underlying tissue from toxic chemicals.

Question 40

What and where is the basement membrane?

Answer 40

The thin, flexible, acellular layer which lies between the epithelial cells and the subtending connective tissue.

Question 41

What lays down the basal lamina?

Answer 41

The epithelial cells

Question 42

What is the structure of the basement membrane?

Answer 42

The basement membrane and various other layers. There is also a reticular fibre (type III collagen) layer, the thickness of which can be changed.

Question 43

What is the function of the basement membrane?

Answer 43

A strong, flexible layer to which epithelial cells adhere. Also serves as a cellular and molecular filter.

Question 44

How is the basement membrane related to prognosis of cancer?

Answer 44

The degree to which malignant cells penetrate the basement membrane is related to prognosis.

Question 45

Cell renewal rate in epithelial tissues is normally constant. What can accelerate it?

Answer 45

Injury.

Question 46

How long does it take from cell division in the basal layer of the epidermis to finally being sloughed off?

Answer 46

28 days.

Question 47

How often are small intensinal epithelial cells replaced from the base of the crypts?

Answer 47

4-6 days

Question 48

What are sterocilia? Where might they be found?

Answer 48

Very long microvilli, which may have an absorbative function. Ductus deferens and epididymis.

Question 49

What is the average size of a human cell?

Answer 49

10 to 20 micrometers

Question 50

What makes us the epithelial basement membrane?

Answer 50

Basal lamina (lamina lucida and densa) and lamina reticularis

Question 51

What are microvilli?

Answer 51

Extensions of the cell membrane, core of which is a cluster of actin fialmenets embedded in villin

Question 52

What is metaplasia? Give an example

Answer 52

Transforming to another cell type Stratified squamous epithelium is replaced by simple columnar epithelium with goblet cells

Question 53

What does the basement membrane do?

Answer 53

Molecular filter Regulates cell migration Epithelial regeneration Cell to cell interactions

Question 54

What is a zonula occludens?

Answer 54

A tight junction between cells that makes it virtually impermeable to fluid

Question 55

What is a gap junction?

Answer 55

Permits cells to communicate Can be closed Directly connects cytoplasm Analagous to plasmodesmata in plants

Question 56

What is a desmosome? What is a hemidesmosome?

Answer 56

Desmosome: macula adherens, anchoring junction for cell to cell adhesion. Lateral, help to resist shearing forces in simple and stratified squamous epithelium Hemidesmosome: mediate adherence to the basal lamina.

Question 57

How are most glands formed? What are the secreting cells of a gland called?

Answer 57

By epithelial downgrowths into surrounding connective tissue Parenchyma

Question 58

Define a gland.

Answer 58

An epithelial cell or collection of cells that are specialised for secretion

Question 59

How are glands classified by destination?

Answer 59

Exocrine: a gland with ducts that open into the lumen of an organ or onto the surface of the skin Endocrine: a gland that secretes directly into the bloodstream or lymphatic system, ductless. Arranged as cords, follicles or clusters around a profuse blood supply for transport

Question 60

How are glands classified by structure?

Answer 60

Unicellular, such as goblet cells, release secretion onto surface epithelium Multicellular: duct system, extends from surface to underlying connective tissue Uncoiled, coiled Simple, complex Unbranched, branched

Question 61

What is a mixed gland? Give an example

Answer 61

A gland with both endocrine and exocrine components Pancreas Exocrine secretes enzymes through ducts to the duodenum, D2. Acinar cells Endocrine, Islets of Langerhans, Insulin and Glucagon to the blood

Question 62

What is a goblet cell? What does it secrete? What type of epithelium is it?

Answer 62

Unicellular gland Secretes mucin which combines with water to form mucus Mucus onto the apical surface to lubricate respiratory tract, intestines etc Simple columnar eputhlium

Question 63

What is an acinus? Give an example of an organ in which acini are found in

Answer 63

Swelling of secretory glands at the end of a tube The pancreas is multi acinar

Question 64

What types of simple glands are there? Give examples

Answer 64

Simple tubular: intestinal cells Simple coiled: merocrine sweat glands Simple branched tubular: gastric glands, mucous glands of oesophagus, tongue, duodenum Simple branched acinar: sebaceoud glands. Simple acinar is only a developmental stage Acinar is aka alveolar

Question 65

What typre of compound glands are there? Give examples

Answer 65

Compund tubular: mucous glands in mouth, bulbourethral glands in males, testes in the seminiferous tubule Compound acinar: mammary glands Compound tubuloacinar: salivary, pancreas, glands of respiratory tract

Question 66

How are glands classified by their method of secretion? Give examples

Answer 66

Merocrine: exocytosis, most glands. Salivary glands, pancrease Holocrine: disintegration of the entire cell, sebaceous gland disintegrate to fill hair follicle with sebum Apocrine: Non membrane bounded lipid secretion, mammary glands, myoepithelial cells assist

Question 67

How are glands classified by their nature of secretion? How effectively are they stained by H and E?

Answer 67

Mucous: contain mucus and are high in mucins, which are highly glycosylated polypeptides. They stain poorly with H and E. Serous: often contain enzymes, are watery and free of mucus. Stain pink with H and E, so are eosinophilic.

Question 68

Describe the process of merocrine secretion

Answer 68

Membrane bound vesicle approaches cell surface Fuses with plasma membrane Contents of vesicle released into extracellular space Plasma membrane is transiently larger Membrane is retrieved which stabilises the cell surface area

Question 69

Describe apocrine secretion

Answer 69

Non membrane bound lipid particle approaches the cell surface Fuses with the plasma membrane, pushes up apical membrane Thin layer of apical cytoplsam drapes around the droplet, surrounding droplet pinches off the cell Plasma membrane transiently smaller Membrane added to regain cell surface area

Question 70

Describe holocrine secretion

Answer 70

Disintegration of entire cell Release of contents Discharge of the whole cell

Question 71

What is endocytosis?

Answer 71

Engulfing of material initially outside of the cell Opposite of exocytosis Coupled wtuih exocytosis in transepithelial transport

Question 72

What is transepithelial transport?

Answer 72

When a molecule is too large to penetrate membranes it can be shunted across from one bodily compartment to another Material is endocytosed at one surface Transport vesicle shuttles it across the cytoplasm Vesicle and material is exocytosed at the oppostie surface

Question 73

Describe the structure of the Golgi apparatus

Answer 73

Stack of disc shaped cisternae One side is flate, the other side is concave Discs have swellings at their edges where vesicles bud off: migratory Golgi vacuoles Cis face to trans face

Question 74

What is the function of the golgi apparatus?

Answer 74

Sorting into different compartments Packaging through condensation of contents Adding sugars to proteins and lipids: GLYCOSYLATION, in the cisternae, vesicles move to the flat face Transport

Question 75

What are the destinations of products from the golgi apparatus?

Answer 75

Majority extruded in secretory vesicles Some retained for use in the cell e.g lysosomes Some eneter the plasma membrane , glycocalyx Or are secreted

Question 76

How does glycosylation in the golgi apparatus increase specificity? What happens if enzymes destory the glycocalyx ?

Answer 76

SUGARS MAKE MOLECULES MORE SPECIFIC Branching sugars offer complex shapes for specific interations in the glycocalyx Destruction of the glycocalyx by enzymes alters specificity of cells: adhesions to substrates and neighbouring cells, communication with neighbouring cells, contact inhibition of movement and division, mobility of cells

Question 77

Name 4 types of control of secretion? Examples

Answer 77

Nervous: sympathetic netvous stimulate of the adrenal medulla leads to the release of adrenaline Endocrine: ACTH stimulate release of cortisol from the cortex of the adrenal glands, zona fasciculata Neuroendocrine: Nervous cells of the hypothalamus control the release of ACTH by CRH Negative feedback chemical mechanism: inhibitory effect of high t3/4 on TRH and TSH

Question 78

What are the 3 major salivary glands? What is the nature of secretion from each?

Answer 78

Parotid: serous Sub-mandibular: mixed, mucous and serous Sub-lingual: more mucous but mixed

Question 79

Classify the following glands as exocrine or endocrine Goblet cells in jejunum/colon, Pancreas, Thyroid Gland, Parotid glands, Parathyroid glands, Adrenal glands, Sub mandibular glands

Answer 79

Exocrine: Goblet cells, Parotid glands, Sub mandibular glands Endocrine: Thyroid, Parathyroid, Adrenals Mixed: Pancreas

Question 80

What is a serous demilune?

Answer 80

Artefactual structure squeezed out by conventional fixation Salivary glands A gland with this structure produces both serous and mucous secretions, mixed Mucosal and serosal cells actually aligned in the acinus

Question 81

What type of epithelium is found in the thyroid gland?

Answer 81

Simple cuboidal epithelium

Question 82

What surfaces do mucosal membranes line? Examples What cells do they have?

Answer 82

Certain internal tubes which open to the exterior Alimentary tracts Respiratory tract Mucus secreting cells to varying degrees

Question 83

What is the structure of a mucous membrane? Constitution

Answer 83

Epithelium (type depending on site) lining the lumen of a tube An adjacent layer of connective tissue, the LAMINA PROPRIA In the alimentary tract, there is a layer of smooth muscle, MUSCULARIS MUCOSAE

Question 84

What are serous membranes? What do they envelope? Examples

Answer 84

Serous membranes are two part membranes that line certain closed body cavities (do not open to exterior) They envelope the viscera/organs Examples Peritoneum envelopes the abdominal organs Pericardium envelopes the heat Pleural sac envelopes the lungs

Question 85

What is secreted by serosal membranes? What is the function of this? What are the two layers of a serosal membrane called?

Answer 85

Secretes lubricating fluid Promotes relatively friction free movement of structures that they surround Visceral (inside) and parietal (outside)

Question 86

What does a serosal membrane consist of?

Answer 86

Simple squamous epithelium MESOTHELIUM which secretes a watery lubricating fluid A thin layer of connective tiossue which attaches to epithelium of adjacent epithelium, and carries blood vessels and nerves

Question 87

What is the gut mesentry?

Answer 87

Double layer of peritoneal membrane which supports the small intestine

Question 88

Describe the layer structure of the alimentary tract

Answer 88

Mucosa: epithelium, basement membrane, lamina propria (aggregrates of lymphocytes, Peyers patches, loose connective tissue), muscularis mucosae Submucosa: connective tissue layer, arteries, veins, nerves Muscularis externae: circular muscle inside, longitudinal muscle outside, peristaltic waves Serosa: mesothelium if peritoneal OR Adventitia: loose connective tissue if retroperitoneal (behind)

Question 89

Describe the layer structure of the oesophagus

Answer 89

Epithelium: stratified squamous non-keratinised Lamina propria: loose connective tissue with blood and lymph vessels, some smooth muscle and immune cells Muscualris mucosae: smooth muscle thin layer Submucose: subtending layer of connective tissue with mucus secreting glands Muscularis externa: circular and longitudinal smooth muscle, peristalsis Adventitia: thin outermost layer of connective tissue

Question 90

Describe the layer structure of the stomach?

Answer 90

Gastric mucosa: secretes acid, digestive enzymes and gastrin. Simple columnar epithelia for absorption. RUGAE: folds of the gastric mucosa forming longitudinal ridges in an empty stomach. Muscularis mucosae Sub mucosa Muscularis externa: oblique, circular and longitudinal layers of smooth muscle

Question 91

Describe the layer structure of the jejunum

Answer 91

Pilicae circulares: circular folds of mucosa and submucosa that project into the gut lumen. Jejunal mucosa: epithelia (simple columnar), lamina propria, muscularis mucosae Submucosa Muscularis externa: circular and longitudinal smooth muscle

Question 92

Describe the layer structure of the large intestine/colon

Answer 92

Epithelium: simple columnar for absorption Crypts of lieberkuhn producing lots of mucus and supplying cells to the surface. Absorbs water and electrolytes on the surface. Structure same as rest of GI tract: mucosa, submucosa, muscularis externae, serosa

Question 93

What makes up the conducting portions and respiratory portions of the respiratory tract?

Answer 93

Conducting: nasal cavity to the bronchioles Respiratory: Bronchioles to the alveoli

Question 94

What is the layer structure of the trachea?

Answer 94

Epithelium: pseudostratified ciliated Submucosa: connective tussue with sero mucous glands which decrease as they go closer to the bronchioles Fibroelastic membrane with trachealis muscle C shaped Hyaline cartilage: C shaped to prevent oesophageal collapse, also in bronchus but no further. Adventitia: loose connective tissue.

Question 95

Describe the layer structure of the bronchus

Answer 95

Pseudostratified epithelium Smooth muscle Submucosa Crescent shaped cartilage

Question 96

Describe the layer structure of a bronchiole

Answer 96

Simple columnar/cuboidal/ciliated. Samller bronchioles are not cilitaed. In terminal bronchioles small sacs extend, lined by ciliated cuboidal epithelium Smooth muscle Alveoli: no cartilages because surrounding alveoli keep the lumen open

Question 97

What are the cell types of the alveoli? What are their functions?

Answer 97

One cell thick, purely epithelial Type 1 cells: squamous, cover 90% of surface area and permit gas exchange with capillaires Type 2 cells: cuboidal, cover 10% of the surface area. Produce surfactant. Numeroud macrophages line the alveolar surface, phagocytose particles Gas exchange across blood air barrier Alveoli are surrounded by a basketwork of capillaries and elastic fibres

Question 98

Describe the layer structure of the ureter in the urinary tract

Answer 98

Transitional epithelium Lamina propria: fibroelastic Muscularis externa: circular

Question 99

Describe the layer structure of the bladder wall

Answer 99

Transitional epithelium, impermeable to urine due to thick plasma membrane and intercellular tight junctions Smooth muscle in the lamina propria Muscularis externae, three interwoven layers

Question 100

Describe the layer structure of the urethra How long is it in males and females?

Answer 100

Transitional epithelium. In penile urethra the epithelium is stratified columnar. Lamina propria Muscularis externae, circular and longitudinal Adventitia Stellate (star shaped) urethral lumen becomes ovoid as urine passes through

Question 101

Describe the regenerative capabilites of various glands

Answer 101

Glandular cells of the mucous membranes of the digestive, respiratory and urinary tractscontinue to multiple throughout life, cells from the apical surface are continually replaced Liver, thyroid and pancreatic cells cease to multiply at puberty, but can regenerate in the case of tissue injury

Question 102

What is neoplasia?

Answer 102

A malignant neoplasm derived from glandular epithelium is called an adenocarcinoma

Question 103

# Define the term limit of resolution

Answer 103

The minimum distance at which two objects can be distinguished at

Question 104

Why are electron microscopes capable of finer resolution than light microscopes? What is the theoretical limit of resolution of light and electron microscopes?

Answer 104

The limit of resolution is proportional to wavelength Electrons, much shorter wavelength than visible light Light: 0.2mm Electron: 0.002nm

Question 105

What are the main differences between prokaryotic and eukaryotic cells?

Answer 105

Prokaryotic: no internal membranes, all processes in one compartment Eukaryotic: compartmentalised by internal membranes, ordely biochemical processes

Question 106

Describe the properties and functions of membranes

Answer 106

Phospholipid (amphipathic molecules) bilayer Proteins are freely mobile, fluid mosaic Some proteins within the membrane are attached to the cytoskeleton Some proteins are glycosylated, pointing outwards, forms the glycocalyx FUNCTIONS: intercellualr adhesion, recognition, signal transduction, compartmentalisation, selective permeability, exocytosis and endocytosis

Question 107

Describe the nucleus

Answer 107

Contains DNA, nucleoproteins and RNA Dense heterochromatin and lucent euchromatin Inactive: small and dense Active: large and sparse

Question 108

Describe the nucleolus

Answer 108

Electron dense structure Site of ribosomal RNA synthesis for ribosome assembley, sub units exported Disappears in cell division

Question 109

Describe the nuclear envelope

Answer 109

Double layer of membranes Nuclear pores Type of special ER, the perinuclear cisterna between inner and outer nuclear membranes, is continuous with the ER

Question 110

Describe the rough ER

Answer 110

Ribosomes on surface Protein synthesis site Generates proteins for transport out of cell or to lysosomes Flattened cisternae Extensive Interconnecting membranes, vesicles Lysosomal enzymes made here, N linked glycosylation, intial

Question 111

Describe the structure of cilia

Answer 111

Nine pairs of peripheral microtubules Two single central microtubules Plasmolemma covered extensions of cytoplasm Move material along the cell surface

Question 112

Describe the smooth ER

Answer 112

No ribosomes Lipid and steroid synthesis: liver, mammary glands, testis, adrenals Not as flat as rough ER, less extensive Intracellular transport Continous with rough ER enclosing single lumen

Question 113

Describe the golgi apparatus

Answer 113

Stacks of cisternae, cis and trans face Prioteins from the rough ER bud off and fuse with the convex cis face Proteins migrate to the concave trans face Sort, concentrate, package and modify proteins O linked glycosylation, add mannose 6 phosphate marker for lysosomal enzymes

Question 114

Describe lysosomes

Answer 114

Generated by the Golgi apparatus Hydrolytic enzymes pH 5 Highly glycosylated membrane for protection Diverse in shape Primary and secondary - phagolysosome Many found in neutrophils and macrophages

Question 115

Describe peroxisomes

Answer 115

Roughly spherical Granualr matricx bound by single membrane Self replicating, no genome in all cells, especially the liver and kidney Major sites of o2 utilisation and H2O2 production Detoxification Oxidises phenols, alcohols, fomic acid, formaldehyde

Question 116

Describe mitochondria

Answer 116

Double membrane with inner membrane in ditinct folds, cristae Generation of ATP by oxidative phosphorylation Main substrates are glucose and fatty acids Matrix: enzymes and mitochondrial DNA, own genetic info, can divide. Female lineage Inner membrane is impermeable to small ions ATP synthase enzymes Endosymbiosis theory Many found in the liver and skeletal muscle

Question 117

Describe the cytoskeleton

Answer 117

Maintains and changes cell shape Structural support for the plasma membrane and organelles Means of movement inside the cell Contractiblity in muscles Locomotor mechanisms for amoeboid movements like lymphocytes, and also for cilia and flagella

Question 118

Describe microfilaments

Answer 118

Part of the cytoskeleton 5nm diameter Two strings of actin twisted together Associated with ATP - contractile Can assemble and dissociate, so is dynamic Core of actin filaments maintains microvilli

Question 119

Describe intermediate filaments

Answer 119

Part of cytoskeleton Not dynamic, 10nm diameter Commonn in nerve and neuroglial cells Also common in epithelial cells that are made of cytokeratin. Tough supporting meshwork in cytoplasm and atr anchored to plasmamebrane at strong intracellular junctions - desmosomes Forming nuclear lamina

Question 120

Describe microtubules

Answer 120

Part of cytoskeleton 13 alpha and beta subinits polymerise to form the wall of the hollow microtubules Originate from the centrosome Found at sites where structures in crlld are moved Long hollow cylinders of tubulin, 25nm diameter 9+2 arrangement in cilia and flagella Attachment proteins can attach to organelles and move them along microtubules

Question 121

# Define the term connective tissue Explain some functions

Answer 121

A tissue of MESODERMAL origin With three basic components: cells, extracellular fibres and ground substance If forms a huge continnum throughout the body, linking together muscle, nerve and epithelial tissue, in a strcutural, metabolic and physical way Its functions include supporting organs, filling spaces between them and forming tendons and ligaments

Question 122

What are the main functions of connective tissue?

Answer 122

Provide substance and form to body and organs Medium for nutrient and waste diffusion Attach muscle to bone, and bone to bone Cushion between tissues and organs Defend against infection Aid in injury repair

Question 123

What are the main resident cell types in connective tissue?

Answer 123

Fibroblasts: synthesise and maintain extracellular components. Synthesise collagen, elastin and reticular fibres and ground substance. Fibrocytes are mature and less active cells. Mesenchymal cells: undifferentiated cells, differentiate into other cells and maintain extracellular materials Macrophages: tissue histocytes derived from monocytes. Ingest foreign material such as bacteria, dead cells and cell debris. Specific names, in liver KUPFER cells, in CNS MICROGLIAL cells, in bone OSTEOCLASTS.

Question 124

How do different connective tissue types vary in their composition?

Answer 124

Cell type Abundance and densitry of cells Constitution of extracellular matrix Ground substance composition Fibre type, abundance and arrangement

Question 125

What are the main visitant cell types in connective tissue?

Answer 125

Mast cells: seen near blood vessels containing granules with histamine and heparin. They release phamacologically active molecules. Plasma cells: derived from lymphocytes. Fat cells - adipocytes: occur in small clusters or aggregates acting for storage. They store lipids and act as an insulator and shock absorber, cushioning organs and joints. Leukocytes (WBCs) - derived from blood vessels, responsible for the production of immunocompetent cells

Question 126

What does the extracellular matrix of connective tissue define?

Answer 126

Whether the function is of primary mechanical importance or if it is loose packing material

Question 127

What are the classes of connective tissue?

Answer 127

Embryonic: mesenchyme (gives rise to others) from mesoderm, mucous connective tissue Connective tissue proper: loose (areolar), dense (regular/irregular) Specialised: adipose, blood, cartilage, bone, lymphatic tissue, haeemopoietic tissue

Question 128

What makes up ground substance in connective tissue?

Answer 128

Gel like matric which the fibres and cells are embedded in, and the ECF diffuses through it Core proteins with glycosaminoglycans attached (GAGs) , proteoglycans and glycoproteins Hyaluronic acid molecules with many proteoglycan molecules, incterweave with collagen fibrils Negative charges on GAGs attract water, forming a hydrated gel

Question 129

What fibres are found in connective tissue, explain a bit about each

Answer 129

Collagen: occurs as bundles of non elastic fibres of varied thickness. Lots of different types but most commonly type 1, synthesis is on RER of cells. Reticular fibrils: type III collagen, thin branching fibres. Delicate network around smooth muscle cells, some epithelial cells, blood vessels, adipocytes and nerve fibres. Also makes the structural framework around organs such as the spleen, liver, bone marrow and lymphoid organs. Elastic: highly elastic, able to stretch 150% of resting length due to lysine content. Composed of amorphous protein, elastin and surrounded by fibrillin.

Question 130

Explain types of collagen and its distribution in the body

Answer 130

Type I: 90% of collagen, tendons, skin dermis, organ capsules, fribrils, fobres, fibre bundles Type II: no fibres, hyaline and elastic cartilage Type III: RETICULIN, fibres around muscle and nerve cells, within lympathic tissues and organs Type IV: basal lamina of the basement membrane Most common protein in the body Tunica adventitia 28 types

Question 131

Describe the type I collagen fibril structure

Answer 131

Periodic banding every 68 nm Each fibril, staggered collagen molecules Each molecule is a triple helix of alpha chains, every third amino acid is glycine, 1.5nm wide Left handed helices into right handed super helix

Question 132

What do fibroblasts secrete?

Answer 132

PROCOLLAGEN Intamitely associated with collagen fibrils

Question 133

Describe the properties and distribution of elastin

Answer 133

Occurs in most connective tissue to varying degrees Primary component of elastic fibres, surrounded by microfibrils called fibrillin Low electron density Found in the dermis of the skin, tunica media of the arteries, elastic cartilage in the epiglottis, ear pinna and eustachian tube

Question 134

What condition is caused by abnormal fibrillin? What are the symptoms of the condition?

Answer 134

Marfan's Tall, arachnodactyly, joint dislocation, aortic rupture

Question 135

What are the different types of loose connective tissue and where are they found?

Answer 135

Blood Mucous connective tiissue e.g. Wharton's jelly Areolar connective tissue, in skin, submucosa, below periteoneal mesothelium, adventitia of blood vessels, surrounding gland parenchyma Adipose Reticular tissue: framework of lymphoid tissues and the liver

Question 136

What are some examples of dense regular connective tissue?

Answer 136

Tendons Ligaments Aponeuroses

Question 137

What are some examples of dense irregular connective tissue?

Answer 137

Skin dermis, periosteum, perichondrium, dura mater, capsules, large septa and trabeculae of organs, deep fascia of muscles

Question 138

What does loose connective tissue do? What is it made up of? What happens to it in oedema?

Answer 138

Forms the septa and trabeculae that make up the framework inside organs and adipose tissue. Divides glands into lobules. Loosely packed fibres that are seperated by amorphous ground substance. Lots of hyaluronic acid, sparse collagen In oedema it becomes greatly distended with ECF

Question 139

What is mucous connective tissue? Where is it found? What it is its composition?

Answer 139

Loose connective tissue: Such as Wharton's Jelly Only found in the umbilical cord and subdermal CTof the embryo Made up of large stellate fibroblasts, which fuse with similar adjacent cells. Some macrophages and lymphocytes are present. The ground substance is soft and jelly like with lots of hyaluronic acid. Delicate mesh of collagen fibres

Question 140

What is areolar connective tissue? Where is it found? What is its composition?

Answer 140

Loose connetive tissue Found deep under the skin, in the submucosa, below the mesothelium of the peritoneum, associated with adventitia of blood vessels, surrounds the parenchyma of glands Contains fibroblasts, macrophages and some mast cells Collagen fibres are the most abundant, but there are some elastic fibres present

Question 141

What is reticular connective tissue? What is it made up of? Where is it found?

Answer 141

Loose connective tissue Made up of type III collagen Forms the framework of lymphoid tissues and the liver

Question 142

What is adipose tissue? What are its properties?

Answer 142

Loose connective tissue Composed mostly of adipocytes, occuring singly or in groups Between collagen fibres Nuclei are often compressed against the cell membrane

Question 143

What is the constitution of dense connetive tissue? What are some properties?

Answer 143

Close packing of fibres Proportionally fewer cells Less ground substance Achieves mecahnical support and transmit forces (tendons)

Question 144

How are fibre bundles in dense regular connective tissue organised?

Answer 144

Fibres in parallel to provide maximum tensile strength

Question 145

What is the composition of ligaments? What do they do?

Answer 145

Collagen fibres interspersed with fibroblasts Less regularly arranged than tendons Elastic ligaments are mainly composed of elastin Connects bone to bone

Question 146

What does a tendon do? What is its composition?

Answer 146

Connects muscle to bone Collagen fibres interspersed withflattened fibroblasts, fascicles (bundles of collagen and fibroblasts), seperated by endotendium (loose CT) and held together by peritendium. A fibrous sheath surrounds the whole tendon

Question 147

What are aponeuroses?

Answer 147

Flattened tendons

Question 148

What is the make up of irregular dense connective tissue? What is its function?

Answer 148

Interwoven bundlesof colagen Small amount of reticular and elastic fibres Counteracts multidirectional forces to which the tissues are subjected

Question 149

Where is irregular dense connective tissue found?

Answer 149

Dermis of the skin, to withstand multidirectional forces and prevent tearing, elastic fibres allow a degree of stretch Capsules of some organs Large septa and trabeculae of many organs Deep fascia of muscles Periosteum Preichondrium Dura mater

Question 150

What is heparin?

Answer 150

An anticoagulant

Question 151

What i histamine and what does it do?s

Answer 151

Increases blood vessel wall permeability Substance attracting neutrophils and eosinophils Secretions for reactions

Question 152

What are the two types of adipose tissue? What are the functions of adipose?

Answer 152

White: single fat droplet in cells Brown: seperate droplets

Question 153

What are some disroders of connective tissue?

Answer 153

Systemic sclerosis: all organs have excessive accumulation of collage: fibrosis, hardening and functional impairment of skin, digestive tract, muscels, kidneys etc Keloid: forms scars on skindue to abnormal amounts of collagen Scurvy: vitamin D deficiencvcy, defective collagen synthesis as cofactor for prolyl hydroxylase. Degeneration of connective tissue, periodontal ligament affected, loosengng of teeth with loss, bleeding gums. Marfan's: defect in gene coding for fibrillin, which affects elastic fibres. Large elastic arteries like the aorta rupture due to bulging caused by a smaller lumen. Ehlers danlos: deficiency in reticular fibres (type III collagen) causing rupture in tissues with high reticulin

Question 154

What are types of variation in the macroscopic structure of human skin?

Answer 154

Colour: ehinicity, site (lips/areolae), UV exposure Hair: site (palms, soles, lips have none), sex (more body hair in men),, age (male baldness, greying), ethinicity (colour, character) Thickness Laxity: site, age, UV exposure (injury to dermal collagen/elastin) Oiliness: puberty, site

Question 155

How do some variation in the macroscopic structure of skin influence the susceptiibility/ manifestations of some skin diseases?

Answer 155

VITILIGO (autoimmune depigmentation): less of a problem in fair skin, hardly noticeable. Psychosocial effects in dark skinned as obvious. ALOPECIA AREATA/TOTALIS (autoimmune hair loss): More impact in women, psychosocial, especially if on scalp. ACNE: common in puberty UV INDUCED: more susceptible in fair skinned, to UV induced acute sunburn, freckling, ageing and skin cancer, especially if red hairded and blue eyed. No sunburn in blacks. Low basal cell carcinoma and malignant melanoma in blacks

Question 156

What is the epidermis made of? What are the different layers of the epidermis?

Answer 156

Stratified squamous keratinsied epithelium, made up mainly of keratinocytes and their products 4 layers Horny layer: stratum corneum Granular layer: stratum granulosum Prickle cell layer: stratum spinosum Basal layer: stratum basale

Question 157

What is the process of keratinocyte differentiation in each of the 4 layers of the epidermis?

Answer 157

Keratinocyte mitosis mainly in the basal layer, the daugther cells then move up to the prickle cell layer. In the prickle cell layer terminal differentiation begins and they lose the ability to divide. Keratinocytes synthesise keratins for strength. Joined by prickle like desmosomes. In the granular layer they lose their plasma membrane and begin to differentiate into corneocytes. This layer contrains keratohyalin granulesm, which are aggregations of keratins, other fibrous proteins (filaggrin and involucrin) and enzymes which degrade membranes. The horny layer is made up of layers of flattened corneocytes, highly keratinised squams, they have a major role in skin barrier function.

Question 158

What are keratins? What are they found in?

Answer 158

Heterodimeric fibrous proteins Epidermis Hair Nails

Question 159

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

Answer 159

30 to 40 days

Question 160

What other epidermal cells are there besides keratinocytes? What do they do and where are they found?

Answer 160

MELANOCYTES: dendritic cells of neural crest origin. Occur at invtervals along the basal layer. DIfficult to see without special stains. They produce melanin, the main skin pigment, more melanin is produced in dark skin. LANGERHANS CELLS: dendritic cells of bone marrow origin. Scatted throughout the prickle cell layer. Difficult to see without special stain. Specialised capacity to present antigens to T lymphocytes and mediate immune reactions - allergic contact dermatitis

Question 161

What are some disorders of the epidermis?

Answer 161

Psoriasis Akkergic contact dermatitis Malignant melanoma Vitiligo

Question 162

Describe psoriasis

Answer 162

A disorder of abnormal epidermal growth and differentiation Common: 1 in 50 people Cause is unknown, but runs in families Autoimmune and T cell mediated Extreme proliferation of epidermal basal layer, causing gross thickening of the prickle cell layer Production of excessive stratum corneum Clinically manifests as excessive scaling Treat with immunosuppresant Often causes psychosocial issues

Question 163

Describe allergic contact dermatitis

Answer 163

Mediated by Langerhans cells Present antigens to T lymphocytes Often in response to nickel

Question 164

Describe malignant melanoma

Answer 164

Aggressive neoplasm of melanocytes Retention above basement membrane of epidermis is associated with good prognosis More penetrating nodular melanomas have a poor prognosis Common moles are benign growths of melanocytes, sometimes hard to distinguish from melanomas clinically

Question 165

Describe vitiligo

Answer 165

Autoimmune attack of melanocytes Causes depigmentation Often symmetrical, may be due to neural control down to neural crest embryological origin of melanocytes Much more visible in dark skin, psychosocial issues

Question 166

What is alopecia areata?

Answer 166

Autoimmune attack of hair follicles

Question 167

Describe the dermo-epidermal junction

Answer 167

Basement membrane below the basal layer of the epidermis Best seen with a PAS stain: Period Acid Schiff InterdigitatingB asal cells connected by hemidesmosomes

Question 168

What is the structure of the dermis?

Answer 168

Dense irregular connective tissue: spiindle shaped fibroblasts. ECM main constituent with mainly type 1 collagens and elastins Blood vessels: small in the superficial dermis, large in deeper dermis. Lymph vessels Mast cells: arround blood vessels, histamine release in allergic reaction, leakage of plasma causing oedema. Nerves: cutaenous sensory nerves transmit sensation

Question 169

What is the main component of scar tissue?

Answer 169

Collagen

Question 170

What causes birthmarks and port wine stains?

Answer 170

Birthmarks: malformation of blood vessels Port wine stain: congenital malformation of blood vessels, always dilated

Question 171

What is the result of damage to collagen and elastin?

Answer 171

Solar elastosis Stretch marks: straie Scars: keloids

Question 172

What are examples of skin appendages?

Answer 172

Hair follicles and sebaceous glands: pilosebaceous unit Sweat glands: eccrine/apocrine Nails

Question 173

Describe a pilosebaceous unit

Answer 173

Sebaceous gland feeds into the hair follicle, side of hair shaft Sebaceous glands are a branched type of acinar gland Holocrine secretion of sebum, cell distintegration Arrector pili muscle for goosebumps Large on face, produce lots of sebum, obstructed in acne- infection

Question 174

Describe eccrine and apocrine sweat glands

Answer 174

ECCRINE: major sweat glands, found in skin and porduce clear odourless substance of water and NaCl which is reabsorbed in the duct. Active in thermoregulation, controlled by the hypothalamus. Composed of intraepidermal spiral duct, stright dermal portion and coiled acinar portion in the dermis APOCRINE: large sweat glands, most abundant in axillae (underarms), genital and submammary areas. No function of value, produce odourless protein rich apocrine secretion. Digestion by cutaneous microbes produces odour.

Question 175

What are the main functions of the skin?

Answer 175

Barrier function: stratum corneo prevents exogeneous absorption. Much studies as most be overcome by percutaneous absorption of drugs, can be disrupted in disorders like psoriasis (loss of fluid, protein, nutrients, heat. Excessive exogeneous absorption) Sensation: sensory nerves allow sense of touch, temperature, tissue damage. Disrupted in leprosy (peripheral nerves disorder) and diabetic sensory neuropathy Thermoregulation: vascular dilation leading to heat loss, contriction retains heat, gives pallor. Failure leads to serious consequences. Eccrine sweating, evaporation. Psychosexual communication: manipulated as a means of communication and expression, tattoos and piercings

Question 176

What are some properties and functions of cartilage?

Answer 176

Non-vascular, strong, pliable Semi solid, firm, tough jelly Support of organs, articulating surfaces of bones, greater part of the fetal skeleton

Question 177

Describe the composition of cartilage generally

Answer 177

Originates from mesenchyme which differentiates into chrondorblasts, which secrete the matrix The matrix surround and entraps these cells in lacunae, they are then referred to as chondrocytes Isogenous clusters of cells Ground substances made up of type I collagen, glycosaminoglycans, gproteoglycans Lots of hyaluronic acid for resistance to pressure No inorganic substances Mesenchymal cells

Question 178

What usually surrounds cartilage? What type of connective tissue is this? What are its layers?

Answer 178

Perichondrium Dense irregular connective tissue Couterfibrous layer, and inner cellular (CHONDROGENIC) layer with chondroblasts

Question 179

How does cartilage develop in the embryo?

Answer 179

Cartilage first appear in the 5th week of development Embryo skeleton composed of hyaline cartilage, until it is replaced by bone Hyaline cartilage remains in the epiphyseal growth plates and articular cartilage

Question 180

Describe where hyaline cartilage is found

Answer 180

Respiratory passages: C shaped cartilage Articulating surfaces of long bones Anterior ends of the ribs Fetal skeleon Nose Epiphyseal growth plates

Question 181

Describe the structure and function of hyaline cartilage

Answer 181

Matrix with proteoglycans, hyaluronic acid and type II collagen, bound to fine collagen matrix fibres Has perichondrium except on articular surfaces Avascular so must rely on diffusion for nutrient supply Offers firm and flexible support Only singular chondrocytes

Question 182

Describe where elastic cartilage is found

Answer 182

Ear (pinna) Eustachian tube Epiglottis

Question 183

Describe the structure and function of elastic cartilage

Answer 183

Matrix is like hyaline cartilage With collagen and many elastic fibres Has perichondrium and is avascular Provides support and maintains the shape of structures Gives extra flexibility, easier rebound

Question 184

Describe where fibrocartilage is found

Answer 184

Intervertebral discs Menisci of the knee Pubic symphysis Portions of the tendons Temporomandibular joint Sterno clavicular joint

Question 185

Describe the structure and function of fibrocartilage

Answer 185

Matrix like hyaline cartilage Abundant type I collagen in thick bundles Gives support and rigidity, strongest cartilage Very strong and resistant to stretching and compression, weight bearing Cells in rows in isogenous groups No perichondrium

Question 186

What is an articular surface?

Answer 186

Where bones and joints meet

Question 187

Describe how cartilage grows

Answer 187

Appositional growth inwards from the periphery, perichondrium Deeper in cartilage, interstitial growth from isogenous groups

Question 188

What clinical conditions can arise concerning hyaline cartilage?

Answer 188

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

Question 189

How does elastic cartilage differ from hyaline cartilage when an individual ages?

Answer 189

It does not calcify/ossify in old age

Question 190

What clinical conditions can arise concerning fibrocartilage?

Answer 190

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

Question 191

What are the characteristics of bone?

Answer 191

Hardest tissue in the bone: can withstand compression, stress and deformation High vascular and well supplied with lymphatics and nerves (especially sensitive to pain in the periosteum) Contains cells, fibres and ground substance (calcified matrix)

Question 192

What are the main functions of bone?

Answer 192

Support Protection Mineral storage (calcium and phosphate) Haemopoiesis

Question 193

What are the two types of bone?

Answer 193

Spongey/cancellous/trabecular/medullar bone Compact/dense/cortical bone

Question 194

What is the structure of compact bone?

Answer 194

Hard, outer bone layer 80% of skeletal mass Covered and lined by connective tissue, PERIOSTEUM, tough, vascular fibrous layer Concentric lamellae with central neurovascular Haversian Canal, which communicate via Volkmann's canals Concentric circles are osteons

Question 195

What is the structure of spongey bone?

Answer 195

Deep, porous, highly vascular Meshwork of trabeculae filled with marrow, fine bony columns No haversian or volkmann's canals Irregular lamellae remodelled by osteoblasts and osteoclasts Osteocytes in lamellae

Question 196

What is marrow made up of?

Answer 196

Red marrow: RBC synthesis Yellow marrow: WBC synthesis Marrow cavity is lined with a thin cellular layer: ENDOSTEUM

Question 197

What is the difference in structure of immature and mature bone?

Answer 197

Immature bone: random arrangement of osteocytes - woven bone Mature bone: osteocytes arranged in concentric lamallae of osteon. Reabsorption cancals parallel with long axis

Question 198

What cells are found in bone? Describe each type

Answer 198

Osteogenitor - OSTEOBLASTS: synthesise the organic components of bone, making bone. They produce the osteoid matrix. OSTEOCYTES: found in lacunae cavities, maintaining bone. Trapped osteocytes. Slender cytoplasmic process, reach out to adjacent osteocytes via canaliculi. Nutrient transfer, also connect with central Haversian canal. OSTEOCLASTS: large multinucleated cells from monocytes, which digest bone. Release H+ ions, lysosomal enzymes.

Question 199

Describe the composition and properties of the bone matrix

Answer 199

65% inorganic, 35% organic Calcium hydroxyapatite crystals, calcium phosphate, calcium carbonat 23% Type 1 collagen, 10% water, 2% non collagen proteins Hardness and rigidity is due to interactions between calcium salts and collagen Flexibility is due to collagen

Question 200

What is the primary microstructure of bone - woven, immature bone

Answer 200

First bone to appear in development and repair, then replaced by mature bone Collagen fibrils arranged randomly in an interwoven fashion More cells and less minerals

Question 201

What is the secondary microstructure of bone - lamellar, mature bone

Answer 201

Compact dense bone: series of haversian canals, osteon, consisting of concentric lamellae of bone laid around a central canal containin blood vessels Spaces between Haversian systems are filled with bony lamellae (interstitial lamellae) Outer surface has extended lamellae (circumferential) Songey bone: meshwork of bone plates which are filled with marrow,. ALways surrounded by compact bone

Question 202

Briefly explain endochondral ossification

Answer 202

Cartilage to bone Cartilage is reabsorbeds and replaced with bone Begins at the primary centre in the diaphysis Later at each end at the seconday centre in the epiphyses Growth in length is at the epiphyseal growth plates

Question 203

Briefly explain how loose connective tissue or mesenchyme becomes bone

Answer 203

Intramembranous ossification Bone begins as highly vascularised loose connective tissue Mesenchymal cells differentiate to osteoblasts, surrounded by collagen fibres and ground substance Secrete uncalcified osteoid and then become osteocytes

Question 204

Briefly explain how bone is remodelled and repaired

Answer 204

ACtions of osteoblasts and osteoclasts Release and incorporation of calcium into and from the matrix

Question 205

what is a fracture?

Answer 205

Bleeding from multiple bleeding blood vesselsHa emotoma between broken bone ends

Question 206

Describe the cellular processes involved in bone repair following a fracture

Answer 206

Bone breaks, bone matrix is destroyed and bone cells adjoining the fracture will die . Blood vessels in periosteum and bone break. Haemtoma forms with fibrous tissue (PRE CALLUS or PRO CALLUS if periosteum is intact). Inflammatory cells invade to form this. New blood vessels into haemotoma, collagen spans break, hyaline cartilage forms. Osteoblsats start to reconstruct spngey bone, OSTEOCALLUS. Calcified to primary then secondary bone. New cancellous bone formed for about two months Bone remodelled via tendons, mechanical stress. Osteoclasts. Mature bone forms Bone heals without forming a scar

Question 207

Describe 5 steps in healing of a fracture

Answer 207

Break Haemotoma PRE/PRO CALLUS Cartilage callus Primary Bone Secondary Bone

Question 208

What are the three types of bone grafts used from bone banks?

Answer 208

AUTOGRAFT: donor is recipient, most successful HOMOGRAFT: donor is different human, may be rejected as foreign HETEROGRAFT: donor is of a different species, least successfulm although calf bone loses antigenicity with refridgeration

Question 209

What are the two types of ossification? Briefly explain the difference

Answer 209

Endochondral: from cartilage Intramembranous: from mesenchyme or loose connective tissue sheet

Question 210

Describe endochondral ossification

Answer 210

Bone formation in hyaline cartilage model, which is reabsorbed and replaced by bone = mineralised Most bones formed in this way, long bones such as femur and humerus STEPS: initial cartilage model, collar of periosteal bone in shaft Central cartilage in diaphyses calcifies, nuterient artery penetrates, osteogenic cells. Primary ossification centre medulla to cancellous bone. Secondary ossification centre at the epiphyses. Epiphyses ossify and growth plates move further apart, increased length Growth in diameter by depostion of bone at periphery of shaft, external modification by osteoblasts to create narrow diaphysis Epiphyseal growth plates replaced by bone when growth stops, hyaline cartilage at articular surface

Question 211

Where does intramembranous ossification occur?

Answer 211

Within condensations of mesenchyme Flat bones: skull (parietal, occipital, temporal, frontal), maxilla, mandible, pelvis, clavicle Also thickens long bone

Question 212

Describe the process of intramembranous ossification

Answer 212

Bone development starts in highly vascularised connective tissue e.g. flat skull bones Focus of activity is primary ossification centre Mesenchymal cells differentiate into osteoblasts, surrounded by collagen fibres and ground substance Osteoblasts secrete osteoid which later calcifieds Osteoblasts become osteocytes, embedded in osteoidMineral depostis in trabeculae radiate outwards from POC

Question 213

How is compact bone formed?

Answer 213

Initially spongey bone is formed Later transformed to compact Structure changes constantly by remoedelling

Question 214

Describe osteogenesis imperfecta (brittle bones)

Answer 214

Group of rare genetic disorders, affecting synthesis of type I collagen by osteoblasts and fibroblasts Weaknesses in structure which rely on collagen for strength: sclearae, skin, tendons, ears, skeleton, teeth, joints Various types: one of which is lethal before birth. Multiple fractures, bone deformities due to weak callus, bowing of bones, thin bones, some have blue sclearae Medicolegal importance as multiple fractures can be confused with deliberate injury = abuse

Question 215

Decribe osteoporosis

Answer 215

Loss of bone mass as age increases, reduced so there is a increased risk of fracture, as no longer provides adequate mechanical support Osteoclasts\> osteoblasts. Inadequate filling of osteoclasts resorption bays Risk areas: neck of femur, vertebral column, distal radius 2 types: Type 1 post menopausal due to loss of osteoclast inhibition by oestrogen. Type 2 senile, after age 70, lss of osteoblast function Risk factors: insufficient calcium intake, insufficient vitamin D, lack of physical activity, cigarette smoking, being female, genetic, blacks have high bone mass peak

Question 216

Describe the consequences of vitamin D and calcium deficiency on bone

Answer 216

Needed for normal ossification, promotes mineralisation of bone Rickets in children: bone matrix does not calcify normally, epiphyseal plate distorted by strains of body weight, bones grow slowly and become deformed. Pliable osteoid, bendy bones, fractures. Bowing of femur, enlarged chostochondral rib junctions, bossing of skull. Osteomalacia in adults: softening of bones. Deficient calcifcation of recently formed bone, partial decalcification of older matrix, causing fragility anf increased risk of fractures. Bone pain, back ache, muscle weakness

Question 217

Explain the importance of vitamin D in normal bone development

Answer 217

Both dietary and skin synthesised, essential for normal ossification As involved in calcium and phosphate absorption in small intestine In its absence, bone is poorly mineralised, a pliable matrix called osteoid (uncalcified, secreted by osteoblasts) Affected bones can't support weight and bend. Common cause of osteomalacia

Question 218

Hoow can osteomalacia be prevented?

Answer 218

Adequate intake of calcium, vitamin D and phosphate Adequate sun exposure (especially in dark skinned individuals)

Question 219

Outline the cause and features of achondroplasia

Answer 219

Congential and often hereditary skeletal disorder, caused by failure of proliferation and column formation of epiphyseal cartilage cells Defect in endochondral bone formation impirs longitudinal growth of the tubular bones, short limbs Skull unaffected as formed by intramembranous ossification Autosomal dominant, gain of function in fibroblast growth factor, increased proliferation of chondrocytes in growth plates, less matrix Epiphyseal growth plates are thin, few cells in the proliferating zone, hypertrophic cartilge cells form irregular columsn, zone of provisional calcified cartilage is smalll and does not provide adequate scaffolding for bone matrix depostion by metaphyseal osteoblasts

Question 220

What is the effect of growth hormone on bone?? Lack and excess

Answer 220

Lack of GH affects epiphyseal cartilage causing pituitary dwarfism if before puberty. After, no effect, no growth plates in epiphyses Excess before pubery, excess long bone growth, gigantism. In an adult, periosteal growth, acromegaly. Usu ally due to benign anterior pituitary tumour

Question 221

What is the effect of sex hormones on bone?

Answer 221

Influence time and appearance of ossification centres Precocious sexual maturity close epiphyseal growth plates prematurely retarding bone growth Sex hormone deficiencies delay plate closure causing tall statuere, later puberty. Androgens and oestrogens influence pubertal growth spurt.

Question 222

What is the effect of thyroid hormone deficiency on bone?

Answer 222

In newborn hypothyroidism causes cretinism Stunted physical and mental development Short stature

Question 223

What are the three types of muscle?

Answer 223

Striated: cardiac and skeletal Non striated: smooth

Question 224

What is the banding structure of muscle?

Answer 224

MHAZI M line is in the H band, which is in the A band Z line is in the I band

Question 225

Describe actin and myosin simply, and where they are

Answer 225

Thin filament is ACTIN, mainly in I band Thick filament is MYOSIN, mainly in A band so H and M too

Question 226

What is a sarcomere?

Answer 226

Z line to Z line distance

Question 227

What forms the thin filaments in skeletal and cardiac muscle?

Answer 227

Actin and tropomyosin molecules wrap around each other Troponin complex attached to each tropomyosin molecule, covering the binding sites for the myosin filament TnI binds to Actin TnC binds to clcium TnT binds to tropomyosin

Question 228

What makes up the thick filament?

Answer 228

Many myosin molecules Heads protrude at opposite endsCent Centre of sarcomere is devoid of heads

Question 229

Describe the sliding filament theory of muscle contraction

Answer 229

A band length is constand Length of the H and I bands decrease Actin filaments move in to overlap with myosin

Question 230

Describe the sarcotubular system of skeletal muscle

Answer 230

AI junction, one transverse (T) tubule T tubule extends from sarcolemma 2 terminal cisternae per tubule, TRIAD

Question 231

Explain the mechanism of the sliding filament model of muscle contraction

Answer 231

Troposmyosin blocks actin binding site for myosin. Calcium ions bind to TnC, moving tropomyosin away, allowing myosin heads to bind actin and begin contraction. 1. Myosin head is tightly bound to actin in rigor conformation. Lack of ATP. 2. ATP binds to the myosin head causing it to uncouple from actin. 3. Hydrolysis of ATP causes uncoupled myosin head to bend and advance 5nm 4. Myosin head binds weakly to actin releasing Pi, causing power stroke. in which myosin head returns to former position. Actin moves to M line, binds to myosin head tightly again. Myosin heads attach at different times causing movement

Question 232

Describe the mechanism of muscle innervatio and excitation contraction coupling

Answer 232

ACtion potential at presynaptic neron terminal, calcium infklux from ECF to ICF Influx causes presynaptic vesicles to release ACh in synaptic cleft ACh binds to nicotinic acetyl choline receptors bound to motor end plate, ligand gated ion channels open allowing sodium ions to diffuse in, depolarising the sarcolemma, spreading to the T tubules Voltage senor proteins of T tubule membrane change their conformation. Gated calcium ion release channels in adjacent terminal cisternae of SR are activated by this Rapid release of calcium into sarcoplasm Calcium binds to TnC, initiating the contraction cycle Calcium ions return to the terminal cisternae of the SR

Question 233

Describe the structure of skeletal mucl from the epimysium to the muscle fibres

Answer 233

Epimysium: thick connective tisssue around muscle, sheath Perimysium: around fascicles, a group of fibres, carries nerves and blood vessels Endomysium: surrounds individual muscle fibresIn Interdigitation of muscle fibres with surrounding connective tissue such as tendon at myotendonous junction - sarcolemma always between collagen bundles and muscle fibres microfilaments

Question 234

What connective tissue is associated with skeletal muscle?

Answer 234

Tendons connect muscle to bone Aponeuroses: muscle to bone or adjoining structures, flat and broad Layers of dense connective tissue bind muscles into functional groups, DEEP FASCIA. Contain large blood vessels, nerves, and some fat.

Question 235

What are muscle fibres (cells) composed of?

Answer 235

Myofibrils, which are composed of myofilaments, actin and myosin Sarcolemma Mitochondria Nucleus

Question 236

How do the A band and I band of skeletal muscle appear under a microscope?

Answer 236

A is dark I is light

Question 237

How are skeletal muscle cells formed?

Answer 237

Derived from the mesoderm, from multipotent myogenic stem cells Give rise to myoblasts, which fuse to form a primary myotube, a chain of multiple central nuclei The nuclei are displaced to the cell periphery by myosin and actin filaments

Question 238

Describe the features of red muscle

Answer 238

Would fnid lots in a marathon runner Smaller Rich vascularisation Rich myoglobin Numerous mitochondria Slow, weak contraction SLow fatigue Rich in oxidative enzymes, poor in ATP ase Few neuromuscular junctions

Question 239

Describe the features of white muscle

Answer 239

Wider Poor vascularisation Little myoglobin Few mitochondria Fast, strong contraction Rapid fatigue Poor in oxidative enzymes, rich in ATPase More NM junctions

Question 240

Describe the main features of skeletal muscle?

Answer 240

Long fibres, cylindrical Many peripheral nuclei Fascicle bundles, tendon connect to bone Somatic neuronal voluntary control Rapid forceful contraction Striated

Question 241

Describe the main features of cardiac muscle

Answer 241

Short branched cylindrical fibres Single central nucleus, 1 or 2 Striated Adherens type junctions join cells end to end, anchor cells and provide achorage for actin Gap junctions for electrical coupling with adjacent cells, intercalated discs, Z bands Intrinsic rhythm, involuntary, autonomic Life long variable rhythm T tubules on Z disc SR less developed, diad not triad

Question 242

Descibr the main features of smooth muscle cells

Answer 242

Spindle shaped with tapering ends Central single nucleus Gap and desmosome type junctions Not striated, no sarcomeres or T tubules Contraction still actin myosin based Slower more sustained contraction, longer Involuntary, autonomic, local stimuli Form sheets, bundles or layers Thick and thin filmaents are arranged diagonally, spiralling down the long axis for a twisting contraction

Question 243

What is the term to describe the spontaneous and rhythmic contractile capabilites of the heart? What sort of cells transmit action potentials from the atrioventricular node to the ventrical walls?

Answer 243

Myogenic Purkinje fibres

Question 244

Describe the microscopic structure of a cardiac muscle cell

Answer 244

T tubules on Z disc Sarcoplasmic reticulum less developed Diad not triad

Question 245

Describe the conduction of the action potential in cariac muscle Describe how purkinje fibres are involved

Answer 245

Action potential in sino atrial node To atrioventricular node Carried to ventricles by purkinje fibres by rapid conduction, enabling the ventricles to contract in a synchronous manner

Question 247

Describe the structure of purkinje fibres

Answer 247

Large cells, modified monocytes ABundant glycogen Sparse myofilaments Extensive gap junction sites

Question 248

Compare the regenerative capabilities of the three muscle types

Answer 248

SKELETAL: cells can not divide by tissue can regenetate by mitotic activity of satellite cells, so that hyperplasia follow muscle injury. Satellite cells fused with existing muscle cells to increase mass, hypertrophy. Gross damage repaired by connective tissue leaving a scar. If nerve or blood supply is interrupted, muscle fibres degenerate and are replaced by fibrous tissues CARDIAC: incapable of regeneration, following damage, fibroblasts invade and divide, laying down scar tissue SMOOTH MUSCLE: reatin mitotic capabilities, can form new smooth muscle cells. Evident in pregnant uterus, muscle wall becomes thicker with hypertrophy and hyperplasia of individual cells

Question 249

Where is smooth muscle found? How is it innervated?

Answer 249

Found in contractile walls of cavities, passageways, vasculature, gut, airways, genitourinary, uterus, ducts, glands, iris Innervated by autonomic, unmyelinated nerves

Question 250

What is the clinical significance of smooth muscle? How can smooth muscle be modified for different functions?

Answer 250

Hypertension, dysmenorrhoea, asthma, atherosclerosis Modified in myoepithelial cells in acini of gland, myofibroblasts producing collagen and contract

Question 251

Explain the use of troponin assays

Answer 251

TnI and TnT are useful markers Cardiac ischaemi Release in one hour Must measure within 20 hours Smallest change in troponin is MI

Question 252

How often are contractile proteins replaced in skeletal muscle?

Answer 252

Every 2 weeks

Question 253

What is atrophy? What problems can it cause and how does it arise?

Answer 253

Wasting of muscle due to lack of use, in the aged, loss of nerve supply following injury. Muscle cell shrinks in size. Disuse atrophy: maintenance requires frequent movement against resistance or fibres shrink and weaken Loss of protein so reduced fibre diameter, loss of power More atrophy with age Destruction is greater than replacement of myofibrils Can also be caused by denervation

Question 254

Describe how atrophy occurs with age

Answer 254

Above the age of 30, muscle mass decreases 50% loss of muscle by age 80 Important in temperature regulation, so loss of non shivering thermogenesis

Question 255

What are the general functions of skeletal muscle?

Answer 255

Movement Posture Stability of joints Heat generation

Question 256

How does muscle atrophy occur due to denervation?

Answer 256

Muscle no longer receives contractile signals which are required to maintain normal size Indications of lower motorneurone lesions include: weakness, flaccidity, muscle atrophy with fasciculatations (spontaenous twitiching of small groups of muscle fibres), and degeneration of muscle fibres 10 to 14 days after injury. Reinnervation within 3 months for good recovery, completely lost after 2 years Muscle fibres are replaced with fibrous and fatty tissue which requires daily stretching as it causes shortening

Question 257

What occurs in hypertrophy of skeletal muscle?

Answer 257

Replacement of fibrils is greater than destruction Increase in muscle mass from work performed against load leads to More contractile proteins, increase in fibre diameter Metabolic changes: enzyme activity for glycolysis, mitochondria, stored glycogen, blood flow Increased muscle length, addition of sarcomeres

Question 258

Outline the physiology of the neuromuscular junction

Answer 258

Motor neurone synaptic knob releases acetyle choline into synapse as a result of calcium influx ACh binds to nicotinic receptor on folded end plate region Sodium ion channel opens, action potential down T tubules Causes calcium ion release from SR, muscle contraction Only 25% of ACh receptors need filling for a contraction

Question 259

What is ACh terminated by? At high motor neurone firing rates, what happens?

Answer 259

ACh is terminated by acetylcholinesterase ACh release decreases at high neurone firing rates

Question 260

Describe the pathophysiology of myasthenia gravis

Answer 260

Automimmune destruction of the end plate ACh receptors and loss of end plate junctional folds Widening of the synaptic cleft

Question 261

Describe the symptoms of myasthenia gravis and when the crisis point occurs

Answer 261

Fatigability and sudden falling due to reduced ACh release, muscle relaxes Drooping eyelids Double vision Affected by general state of health and emotion Test: hold out arm when sat down, see if it collapses quickly Crisis when it affects respiratory muscles

Question 262

How is myasthenia gravis treated?

Answer 262

Acetylcholinesterase inhibitors Stops it beraking down ACh Neostigmine, physostigmine Also can place eyes on the eyelids to decrease acetylcholinesterase activity

Question 263

How is neuromuscular transmission affected in botulism?

Answer 263

Toxins block ACh release Clostridium botulinium bacteria in soill Can not breath properly Used in botox

Question 264

How is neuromuscular transmission affected in organophosphate poisoning?

Answer 264

Inhibits acetylcholinesterase irreversibly ACh remains in the receptors Muscle stays contracted

Question 265

What are muscular dystrophies?

Answer 265

Genetic disorders group Progressive muscle wasting and weakness Failure of body to produce proteins, or not enough, in the muscle cell membrane

Question 266

What is dystrophin?

Answer 266

Long rod shaped protein Anchors sarcolemma to actin and myosin fibrils

Question 267

Describe the pathophysiology of duchenne muscular dystrophy

Answer 267

Complete absence of dystrophin Actin not anchored to sarcolemma, so fibres tear themselves apart on contraction Creatine kinase liberated into serum Calcium enters cell causing necrosis Pseudohypertrophy (swelling), before fat and connective tissue replace muscle fibres

Question 268

Describe the symptoms of duchenne muscular dystrophy Describe some possible treatments

Answer 268

Early onset, Gower's sign, push hands on knees to push strength up Slow, late walking, falls Contractures: stiff joints. Imbalance between agonist and antagonist muscles Steroids: prednisolone, helps to build up muscle fibres Genetic reseatch, to make dystrophin with stem cells, gene therapy. Ataluren drug trials, ribosomal interaction to make dystrophin

Question 269

Give examples of myopathies

Answer 269

Inflammatory: poliomyostitis (chronic inflammation, viral/autoimmune), myalgia (muscle pain) and influenza Electrolyte imbalances: cramps, diuretic therapy (hypokalaemia) Thyrotoxicosis: increased BMR and protein catabolism Hypoparathyroidism: hypocalcaemia causing tetany Channelopathies: malignant hyperthermia

Question 270

Describe the pathophysiology of malignant hyperthermia

Answer 270

Rare, autosomal dominant condition, life threatening reaction to some general anaesthetics Volatile anaesthetic agens and NM blocking agent succinylcholine, which is a non competitive inhibitor of ACh on muscle nicotinic receptors. It is degraded by butyrlcholinesterase much more slowly than ACh by acetylcholinersterase Uncontrolled increase in calcium release in the muscle, and uncontrolled increase in oxidative metabolism, overwhelming body's capactiy to supply o", remove co2 and regulate body metabolism. Heat production, circulatory collapse and death. Can be treated with dantrolene a muscle relaxant

Question 271

How are nerve fibres structured outside the CNS?

Answer 271

Bound together by connective tissue To form the peripheral nerves

Question 272

What are fibres that carry impulses towards the CNS called?

Answer 272

Afferent or sensory fibres

Question 273

What are fibres that carry impulses away from the CNS called?

Answer 273

Motor or efferent fibres

Question 274

What is an entire nerve sheathed by?

Answer 274

Epineurium

Question 275

What is a nerve fascicle ensheathed by? And what travels in this? What is the clinical relevance?

Answer 275

Perineurium Point where blood vessels travel within the nerve Potential malignancy transport

Question 276

What is a single nerve axon ensheathed by?

Answer 276

Endoneurium

Question 277

Describe the structure of a neuron

Answer 277

All neurones have one axon Cell body with or without dendrites Myelinated or unmyelinated Axonal terminal

Question 278

Describe the basic neuron types

Answer 278

Multi polar: multiple dendrites, one axon, motoneuron Bipolar: one dendrite and one axon, interneuron, rare, in retina of eye Unipolar/ pseudounipolar: no dendrites, one axon, sensory neuron

Question 279

Describe how peripheral nerves are myelinated

Answer 279

Sleeve of Schwanna cells, the neurolemma Wound in several concentric layers Discntionous, with gaps called nodes of ranvier To increase the speed of conduction, correlates to level of axonal myelination

Question 280

How are myelin sheaths histologically processed?

Answer 280

Myelin is mainly lipid, so poorly preserved in routin processing techniques Special fixatives and stains Osmium tetroxide

Question 281

How are axons myelinated in the CNS?

Answer 281

Glial cells called oligodendrocytes Produce and maintain the myelin coating Covering up to 250 axons

Question 282

Describe the myelination in the autonomic and somatic nervous systems

Answer 282

Autonomic (involuntary): myelinated (CNS) and unmyelinated (PNS) neurones Somatic (voluntary): all myelinated neurones for faster action potentials

Question 283

What neurotransmitters do excitatory neurones use? What to they do to the next neuron?

Answer 283

Glutatmate/aspartate Depolarise next neuron

Question 284

What neurotransmitters to inhibitroy neurones use? What do they do to the following neuron?

Answer 284

Glycine or GABA (g amino butyric acid) hyperpolarises the next neuron

Question 285

What causes neurotranmitters to be released?

Answer 285

Depo[Add](../new)larisation of the axon terminal Influx of calcium ions Presynaptic vesicles release contents

Question 286

What is the neuron proximal to the synapse called? What is the neuron distal to the synapse called?

Answer 286

Pre synaptic is proximal Post synaptic is distal

Question 287

How does demyelination cause a slowing of conduction veloctiry within a nerve?

Answer 287

Impulse has further to travel as saltatory propagation is inhibitied, slower response EG Multiple Sclerosis

Question 288

Describe multiple sclerosis

Answer 288

The myelin sheath is destructively removed from the axon and replaced by scar tissueOligodendrocytes and axons can also be damaged Condction velocity and saltatory propagation is impaired Scar tissue does not permit conduiction therefore the axon is useless

Question 289

Describe the structure of a nerve cell body (perikaryon)

Answer 289

Engine of neurone, 4 to 120 micrometres in diameter Varies in shape, may have dendrites, axonal hillock last site of summation Nissl substane, aggregration of RER for protein synthesis Golgi packages neurotransmitters into vesicle

Question 290

Describe dendrites

Answer 290

Specialisations to increase cell body surface area From cell body, proximal, further away, distal Dendritic tree Dendritic spines for learning experiences, Down's can't express Does not matter where the signal is received, it is maintained

Question 291

Describe the variety of connections between neurones

Answer 291

Lightly (one cell to one cell) to heavily (one nerve cell to thousands)

Question 292

How many pairs of spinal/segmental nerves are there?

Answer 292

31

Question 293

What s the nervous system made up of? What are nerves from the brain called?

Answer 293

Brain, spinal cord and nerves Cranial nerves

Question 294

How is the central nervous system encased?

Answer 294

3 layers of connective tissue Meninges

Question 295

What are the 3 meninges, from outside to inside?

Answer 295

Dura Mater Arachnoid Mater Pia Mater

Question 296

What is CSF?

Answer 296

Cerebrospinal fluid Equivalent to arterial and venous fluid of the CNS Formed by choroid plexus of arteries Butrition and oxygenation of CNS neurones, carries away metabolites

Question 297

What are the clinical implications of too much CSF?

Answer 297

Brain death High hydrostatic pressure

Question 298

What are the leptomeninges?

Answer 298

Arachnoid mater and pia mater

Question 299

What is the sub arachnoid space?

Answer 299

The space between the pia mater and arachnoid mater

Question 300

What is within the subarachnoid space? How does it arise?

Answer 300

Cerebral spial fluid flows here, and blood vessels Dilations occur floowing failures of arachnoid mater to follow brain furrows, and adher to pia mater Dilations are CSF cisterns Important clinically to confine brain bleeds

Question 301

What are the two major cell types in the CNS?

Answer 301

Neurons, functional 10% Glial cells, make sure neurones thrive, 90%

Question 302

What is the function of glial cells generally?

Answer 302

Support neurones, help maintain homeostasis, form myelin, insulate neurones, destroy pathogens

Question 303

What are various glial cell types? What are their functions? Where are they found?

Answer 303

Astrocytes: blood brain barrier, assist in transfer of nutrients and waste, in the CNS Oligodendrocytes: myeliantion, up to 250 axons per cell, in CNS Microglia: immune and inflammatory reactions, macrophages, in CNS and PNS Schwann cell: myelination, many cells per axon, in PNS Satellite cells: physical support of peripheral neurones (afferent and efferent), PNS

Question 304

What are the types of input summation?

Answer 304

+ excitatory - inhibitory SPATIAL: summated with respect to spatial location on cell Temporal: summated with respect to time of arrival on cell body

Question 305

What are the functions of an axon?

Answer 305

Summates all inputs to the neuron Initiates action potentials Conducts action potentialsm away from the cell body to the terminals Depolarisation of terminals leads to release of neurotransmitters Communicates with follower cell

Question 306

What are the functional classes of neurone? Explain each

Answer 306

Sensory, pseudounipolar: receptros that transduce to electrical impulses . Conduct to cell body, then spinal cord/brain , some are fastest conducting neurones in body, AFFERENTS Motor, multipolar: carry out brain instructions to move muscles, conduct from brain to muscle, largest neurones, integrate large array of inputs to one output, clinically very important. EFFERENTS Inter, multipolar: 95% of nervous system, smallest, wholly in CNS, info relays between sensory and motor neurones, probably most complex neurones in the body. RELAYS

Question 307

Describe the cell membranes of neurones

Answer 307

Bilipid, selectively permeable to certain ionic species. Development of ionic concentration gradients between inside and outside of cells. ELECTROCHEMICAL GRADIENT Makes the neurone electrically charged

Question 308

How are ion channels gates on neurones?

Answer 308

Voltage gates: opened or closed by voltage changes Others opened by nurotransmitters: ligand gated

Question 309

What value is the neuron hyperpolarised at? resting potential

Answer 309

-70mV

Question 310

Describe the charges of the neuron at rest

Answer 310

Net negartive inside, net negative outside Active transport of Na+/K+ pumps More sodium out, potassium in 3:2, potassium can get back out, sodium can't get back in

Question 311

Describe how an action potential is generated?

Answer 311

Stimulus above threshold -55mV, causes Na+ channels to open, Na+ flows back in, membrane is depolarised, local area positive Depolarisation moves along membrane After actional potential, K+ channels open, flow out and restore the resting potential Goes too far: refractory period

Question 312

What is a ganglion?

Answer 312

Accumulation of nerve cell bodies outside the CNS Afferent cell bodies are in the spinal or cerebral ganglia in the dorsal root of spinal nerves

Question 313

What is the autonomic nervous system?

Answer 313

The involuntary nervous system

Question 314

What are the two main divisions of the autonomic nervous system?

Answer 314

Sympathetic Parasympathetic

Question 315

TheANS is comprised of a series of how many neurones? Describe

Answer 315

Series of 2 neurone, pre-ganglionic and post-ganglionic 1 cell has a cell body in the CNS, the other cell has a cell body in the PNS

Question 316

What to ANS neurones exert actions on?

Answer 316

Viscera Smooth muscle Secretory glands

Question 317

What is grey matter? What is white matter? What is in the central canal? What is used to stain a TS spinal cord?

Answer 317

Grey matter: neuronal cell bodies White matter: neuronal axons CSF in the central canal Cresyl violet stain

Question 318

In the CNS, what is the name for collections of: Neuronal cell bodies? Neuronal axons?

Answer 318

Nuclei Fibre tracts

Question 319

In the PNS, what is the name for collections of: Neuronal cell bodies? Neuronal axons?

Answer 319

Ganglia Nerves

Question 320

How is the nervous system divided into different levels and areas?

Answer 320

CNS and PNS to Afferent and Efferent Efferent to Somatic and Autonomic Autonomic to Sympathetic, Parasympathetic and Enteric

Question 321

Describe somatic efferents

Answer 321

Voluntary Simplest possible layout 1 neurone carries output, terminates directly on effector organs Activate when needed, otherwise inactive Efferents undeveloped at birth, fully developed at puberty

Question 322

What are the functions of the autonomic nervous system?

Answer 322

Fundamental life functions, non stop Balance of opposing systems, sympathetic and parasympathetic Maintains constant homeostasis Promotes excretory mechanisms intermittently

Question 323

Describe autonomic innervation

Answer 323

Most innervated by ANS dually, PNS and SNS Dominance of each depends Exception: sweat = SNS only

Question 324

What happens when the sympathetic or parasympathetic nervous systems are overactive?

Answer 324

SNS overactive: constriction of blood vessels (oreserve heat) , shortage of substrate to body tissues PNS overactive: dilated blood vessels, shortage of substrate to brain

Question 325

Describe CNS and PNS neurones in the autonomic nervouse system

Answer 325

CNS: pre-ganglionic, myelinated, white rami communicantes PNS: post-ganglionic, not myelinated, Grey rami communicantes

Question 326

What is the main function of the sympathetic nervous system?

Answer 326

Involved in the fight/flight/fright response Expressed mainly in stress situations Diversion of blood to muscles and heart, increase in heart rate, increase in blood pressure, reduced blood floow to GIT and skin, pale, hyperventilation.

Question 327

Describe the outflow of the sympathetic nervous system

Answer 327

Thoraco-Lumbar Nerve fibres have cell bodies in all 12 thoracic sections, and first 2 lumbar sections Dorsal, LATERAL and ventral horns in TS spinal cord

Question 328

Describe the two nerve fibres of the sympathic nervous system and their synapsing

Answer 328

Short pre ganglionic, long post ganglionic Paravertabral chain of ganglia along sympathetic trunk, parallel to vertebrae, skull to sacrum May synapse at same levels as origin (paravertebral origin) May synapse a different level to origin May not synapse in the paravertebral chain (splanchnic nerves)

Question 329

Describe the neurotransmitters and receptors in the sympathetic nervous system

Answer 329

Preganglionic neurones are CHOLINERGENIC (Acetylcholine) So post ganglionic receptors are NICOTINIC Post ganglionic receptors are NORADRENERGENIC (noradrenaline) Two classes of adrenoreceptors: alpha 1 and 2, and b 1 and 2 Exceptions: some synapses are cholinergenic, perspiration and ejaculation pathways

Question 330

In the ejaculation pathway, which division of the ANS is responsible for erection? ejaculation?

Answer 330

Erection: Parasympathetic POINT Ejaculation: Sympathetic SHOOT

Question 331

What are the main functions of the parasympathetic nervous system?

Answer 331

BASAL, relaxation, calm Reduced heart rate and force of contraction Promotes digetion Promotes bodily functions such as bladder emptying Promotes sleep

Question 332

Describe the outflow of the parasympathetic nervous system

Answer 332

Cranio sacral outflow

Question 333

Describe the two nerve fibres of the parasympathetic nervous system

Answer 333

Long pre ganglionic Short post ganglionic Post ganglionic neurones in walls of effector organs

Question 334

Describe the neurotransmitters and receptors in the parasympathetic nervous system

Answer 334

Pre ganglionic neurones are CHOLINERGENIC (acetyl choline) Post ganglionic receptors are NICOTINIC Post ganglionic neurones are CHOLINERGENIC Effector organs are MUSCARINIC

Question 335

How can neurotransmitters be exploited in the therapeutic domain?

Answer 335

Agonist (triggers response) and antagonists (block agonists) Beta blockers in heart stop sympathetic stimulation

Question 336

What are blood cells initially produced by in the foetus?

Answer 336

Mesoderm of the yolk sac Liver Spleen Bone marrow

Question 337

What is haemopoeisis?

Answer 337

The production of red and white blood cells, and platelets

Question 338

Describe the process of haemopoeisis

Answer 338

PROLIFERATION:stem cell divides into 2, one replaces the original step cell (self renewal) and the other cell differentiates DIFFERENTIATION: Haemopoetic progenitor will first differentiate to form either a myeloid blast (RBC, WBC, platelets) or a lymphoid blast (immunoresponse cells) The progenitor will differentiate into a certain cell type under the influence of a particular cytokine

Question 339

What is a cytokine? Give some examples

Answer 339

A hormone, signalling molecule Some types cause differentiation of blood cells Erythropoietin: RBCs when pO2 is low Thrombopoeitin: platelets G-CSF, GMCSF, IL-6: colony stimulating factors

Question 340

How many types of white blood cell are there? Where do they circulate?

Answer 340

5 types Blood and lymphatic systems

Question 341

Where do T cells mature?

Answer 341

Thymus

Question 342

Describe Neutrophils

Answer 342

Multilobed nucleus, small granules in cytoplasm (polymorphonuclear granulocyte) Most common circulating WBCs, inactive in circulation, 10 hour lifespan Migrate out to site of infection CHEMOTAXIS PHAGOCYTOSIS G-CSF (granulocyte CSF) increases production

Question 343

Describe eosinophils

Answer 343

Bi lobed nucleus, large granules (polymorphonuclear granulocytes) PHAGOCYTOSIS, of antigen antibody complexes, releases cytotoxic particles Hypersensitivity reactions Lifespan 8 to 12 days Migration to serosa

Question 344

Describe basophils

Answer 344

Quite rare, bi or tri lobed nucleus, dense granules, polymorphonuclear granulocytes Mediate acute inflammatory reactions with histamin and heparin: oedema Also hyaluronic acid and seratonin Half life 2.5 days

Question 345

Describe monocytes

Answer 345

Large kidney shaped single nucleus, mononuclear cells, no granules Migrate to tissues to become macrophages PHAGOCYTOSIS, interact with T cells, CHEMOTAXIS DIAPEDESIS: intact through capillaries Response to inflammatio and antigenic stimuli

Question 346

Describe lymphocytes

Answer 346

Large deep staining nucleus, mononuclear cells B: humoral immunity, stimulated by antigens, transform to plasma cells, secrete immunoglobulins, antibody forming T: express CD4 on surface (helper), can be killer cells, permit transformation of B cells into plasma cells, CD8+ suppressor cells. Mature in thymus Natural killer cells too

Question 347

Describe the structure of erythrocytes

Answer 347

8 micrometre diameter , biconcave disc Carries haemoglobin, 4 globin chains, 2 alpha, 2 beta, each with a haem group Spectrin and actin affect shape Membrane with glycoproteins and antigens If changes in shape, congenital or acquired, removed by spleen

Question 348

What is the lifespan of a red blood cell?

Answer 348

120 days

Question 349

What is the function of an erythrocyte?

Answer 349

Carrie oxygen to the tissues from the lungs, and carbon dioxide to the lungs Maintains osmotic eqbrm of the circulation Generates ATP from glucose making lactate Flexible to pass through narrow capillaries Provides oxygen when low, increase RBC production in response to hypoxia

Question 350

What are the two main metabolic pathways in RBCs?

Answer 350

Glucose to lactate and ATP, glycolysis and lactate dehydrogenase Hexosemonophophate - G6P to ribose sugars by glucose 6 phosphate dehydrogenase to generate NADPH

Question 351

Describe haem catabolism

Answer 351

RBCs broken down in spleen, Hb to Haem The iron is conserved Unconjugated bilirubin yellow Bilirubin conjugated in the liver, more watersoluble with glucaronic acid, less toxic Liver to kidney, urobilinogen, yellow Liver, gall bladder, in bile through bile duct, into intestines stercobilin, brown, egested

Question 352

What does bilirubin in the blood cause?

Answer 352

Yellow colour, in the skin and sclearae Bilirubin produced when prophyrin opens up Toxic Attaches to albumin as not very water soluble

Question 353

Describe the structure and fucntion of reticular cells

Answer 353

Synthesise reticular fibres and surround them with cytoplasm Type of fibroblast, type III collagen Direct T and B lymphocytes to specific regions with the lymphatic tissues

Question 354

What is the structure of platelets? How are they formed?

Answer 354

Small round blue particles Cell fragments, stored in the spleen Produced from megakaryocytes in the bone marrow Complex surface membrane Alpha granules with fibrinogen and von Willebrand's factor Dense granules with ADP and calcium ions

Question 355

What is a reticulocyte?

Answer 355

An immature RBC

Question 356

What is the function of platelets?

Answer 356

Adhesion to damaged cell walls and aggregate together Provides phospholipid surface as a binding site for clotting factors in the cascade Aggregation: release of ADP from granules, glycoprotein receptors exposed Interacts with factors VII, IX and X Fibrin mesh traps platelets and RBCs

Question 357

What does the bone marrow do? Where is it found?

Answer 357

Produces RBCs, platelets and WBCs Extensive bone marrow in infant More limited in adult, mainly pelvis, sternum, skull, ribs and vertebrae Blood cells released into sinusoids then the blood stream

Question 358

What is the reticuloendothelial system?

Answer 358

Part of the immune system, containing phagocytic cells: Monocytes, kupffer cells, macrophages, tissue histiocytes, microglial cells Cells of RES identify and mount an appropriate immune resposne to antigens Main organs: spleen, liver and LN

Question 359

What are the types of T cells?

Answer 359

CD4 helper cells CD8 suppressor cells

Question 360

Describe the components of the innate humoral immune system

Answer 360

Transferrin and lactoferrin, deprive microorganisms of iron Interferons, inhibit viral replication Lysozyme, breaks down petptidoglycan in cell walls of bacteria Antimicrobial peptides Fibronectin: opposes bacteria and promotes their phagocytosis Complemet: causes microbe destruction directly with or without phagocytic help TNF a: suppresses viral replication and activates phagocytes

Question 361

Describe the cellular components of the innate immune system

Answer 361

Macrophages/monocytes: phagocytosis and antigen presentation to lymphocytes Neytrophils: phagocytic and antibacterial Eosinophils: anti parasite and allergic respoinse Basophils and mast cells, allergic response Natural killer cells, recognise and kill abnormal cells such as tumours

Question 362

Describe the humoural components of the adaptive immune system

Answer 362

Cytokines: promote differentation and proliferation of lymphocytes Perforin: released by T killer cells to destroy cell walls Antibodies: protect host by neutralisation, prevents binding to epithelia, opsonisation and complement activation

Question 363

Describe the cellular components of the adaptive immune system

Answer 363

T cells: T helpers which become activated when CD4 binds to a specific antigen on MHC/antigen complex of an antigen presenting cell. Once activated, it clones itself to form active T helper cells and T memory cells T killer, releases perforin when cell is already infected B cells: divide to form plasma cells and memory cells when activated by a T helper, and release cytokines. Plasma cells produce specific immunoglobulins for a non self antigen

Question 364

What are the roles of proteins in pathogens?

Answer 364

Nutrient acquisition Reproduction Respiration Locomotion

Question 365

How is the immune system alerted to damage?

Answer 365

By causing damage, breaking barriers to prosperous regions Detect differences in proteins, different amino acid sequences

Question 366

What does epithelial tissue do as the first barrier to pathogens?

Answer 366

Innate immune system Adaptations to clear pathogens from the surface, cilia, regeration, tears, nasal hairs, coughin, enzymes etc Natural antibiotics Cytokines Chemokines (attracts other cells) When pathogens break through, endothelium is leaky to let cells out, phagocytosis, opsonisation

Question 367

What is opsonisation?

Answer 367

Pathogen marked for ingestion and destruction by phagocyte

Question 368

Describe the features of the innate immune system

Answer 368

Present from birth Non specific Not enhanced by second exposure No memory Poorly effective without adaptive response Cellular and humoral Triggers and amplifies adaptive response Importance shown by rarity of innate inherited disorders

Question 369

Describe features of the adaptive immune system

Answer 369

Arises from exposure to microorganisms Specific pathogen immunity Enhanced by second exposure Acquires memory (memory cells) Poorly effective without innate immunity Cellular and humoral Antibodies reflect infections to which they have been exposed, diagnostic tool

Question 370

When do the innate and adaptive immune systems start to work?

Answer 370

Innate: immediate, quicker to respond Adaptive: slower to respond, multiplication of cells, but lasts much longer after infection

Question 371

What happens if innate or adaptive immune systems are lacking?

Answer 371

Innate lacking: does not respond well at all, microbes quickly multiply Adaptive lacking: innate initially responds, then microbes proliferate