4) Tissues Of The Body

Question 1

What is the function of cilia and flagellate

Answer 1

Allow cells to move

Allow cells to waft substances across their surface eg Fallopian tube, trachea

Question 2

What are centrioles

Answer 2

Cylindrical structures found in animal cells- groupings of microtubules arranged in a 9 + 0 pattern like MTOC (microtubule organising centre- where microtubules emerge).

They help to organise the assembly of microtubules which help the movement of chromosomes or chromatids during cell division.

Question 3

What are the 4 main types of cell junction

Answer 3

Occluding junctions- zonula occludens or tight junctions
Adhering junctions- zonula adherens
Desmosomes- macula adherens - there are also hemidesmosomes that lie on the basal membrane to help stick the cells to the underlying basal lamina
Gap junctions- communicating junctions

Question 4

What are the characteristics of tight junctions (zonula occludens)

Answer 4

• pentalaminar (5 layer structure)
• continuous lines of intramembranous particles- occludins
• prevents the movement of membrane (lipids, proteins and signalling molecules) from apical surface to the lateral surface of the cell.
• limits the movement of water and other molecules through intercellular space

Question 5

What are the characteristics of adherent junction - zonula adherens

Answer 5

• 20nm gap
• cell adhesion molecules- Cadherins, integrins, selectins, immunogobulin superfamily etc
• E cadherin binds to catenin, vinculin, and a-actin
• a actin binds to tonofilaments of actin in cytoskeleton
• E cadherin link to E cadherin require Ca++
• provides mechanical stability by linking cytoskeleton of adjacent cells

Question 6

What are the characteristics of desmosomes - macula adherens

Answer 6

*20nm gap
Discoid
* desmocollin and desmoglein between cells
* intracellular attachment plaques
*link to immediate filaments in cytoplasm
* perpendicular to basement membrane

Question 7

What are hemidesmosomes

Answer 7

They face the basement membrane

Question 8

What are the characteristics of the gap junction - communicating junction

Answer 8

• allow direct communication between adjacent cells
• allow passage of ions, AA, sugars, second messengers, metabolites
• permits co-ordinated cell activity
• made of proteins (connexions) which assemble into channels called connexons

Question 9

What is the function of the extracellular matrix

Answer 9

Helps cells interact with their surroundings

Question 10

What is the extracellular matrix made up of

Answer 10

• ground substance
• fibrous molecules
• structural glycoproteins

Question 11

What is the ground substance of the extracellular matrix

Answer 11

• occupies large volume for small mass
• hydrophilic- attracts water and Na+
• embedded with glycosaminoglycans (GAGs)
• acidic
• negatively charged hydroxyl, carboxyl and sulphydryl groups

Question 12

What are the fibrous molecules of the extracellular membrane

Answer 12

• collagen
• tensile strength
• secreted as tropocollagen and polymerised extracellularly to form collagen - at least 11 different types :
• reticulin - type III collagen - branched
• elastin- stretching and elastic recoil, tropoelastin polymerises to elastin, requires fibrillin for assembly

Question 13

What are the structural glycoproteins in the extracellular membrane

Answer 13

*filamentous
- fibrillin- microfibrils 8-12nm links to elastin
Fibronectin- deposition and orientation of collagen and its links to cells via integrin

• non filamentous- link cells and ECM
• laminin- major component of basement membrane
• entacin- binds laminin to type IV collagen
• tenascin- binds to integrins

Question 14

Summarise simple squamous as : epithelium, mesothelium and endothelium

Answer 14

Simple squamous epithelium- terminal air sacs, part of kidney tubules

Simple squamous mesothelium- linings of body cavities and covering organs that are within them (pleura, pericardium, peritoneum)

Simple squamous endothelium- lining of blood vessels and lymphatics

Question 15

Summarise simple cuboidal epithelia

Answer 15

Found in many glands eg sweat and thyroid glands and portions of their ducts

Question 16

Summarise simple columnar epithelia

Answer 16

Found in gall bladder, surface of stomach, uterus and oviducts

Question 17

What are the surface specialisations of simple epithelia

Answer 17

• cilia (oviduct)
• microvilli - striate border (small intestine)
• microvilli - brush border (proximal kidney tubules)

Question 18

Outline the 3 types of stratified epithelium

Answer 18

1) squamous - may be keratinised or non keratinised (cells flatten, lose their nuclei and are filled with keratin as they approach the surface)
2) cuboidal- found in a few ducts of sweat glands
3) columnar - found in ducts of mammary glands and larger ducts of salivary glands

Question 19

Where is transitional epithelium found

Answer 19

Urinary tract, pelvis of kidney, ureter, bladder and part of urethra

Question 20

What are the functions of epithelia

Answer 20

Simple epithelia- absorption eg kidney , gut
Stratified epithelia- protective eg skin, lining of oesophagus
Other functions:
- secretion, sensory perception, movement of materials eg cilia, wound repair

Question 21

What are the cell surface specialisations of microvilli

Answer 21

• apical plasma membrane
• Increase SA
• core of microfilaments
• anchored in terminal web

Question 22

What are the cell surface specialisations of cilia

Answer 22

• apical surface
• very numerous
• transports material across a surface
• microtubules

Question 23

What are the cell surface specialisations of stereocilia

Answer 23

• non motile

- microfilament core - modified microvilli

Question 24

What is the cell surface specialisation function of basal infoldings

Answer 24

Increased SA

Question 25

Define exocrine and endocrine

Answer 25

Exocrine- glands secrete ‘out of’ the body via ducts | Endocrine- glands do not have ducts, but secrete directly ‘into’ the body, into blood capillaries

Question 26

What is the structure of exocrine glands

Answer 26

Tubular, alveolar Simple- where the secretion is conveyed to the surface via an unbranched duct Compound- where the duct branches to form a ductal system

Question 27

What are the 3 different types of secretion

Answer 27

Serous- glands produce a watery fluid Mucous- glands produce a more viscous fluid containing mucin Mixed- glands produce a mixture of serous and mucous fluids

Question 28

What is eccrine (merocrine) glands

Answer 28

Glands in which the glandular cell bodies are not injured or destroyed during secretion ie a cycle of discharge, formation , discharge and reformation occurs

Question 29

What is an apocrine gland

Answer 29

Glands where the secretion gathers at the outer apical end of the secretory cell; the accumulated secretion is pinched off with a portion of the cell cytoplasm but most of the cell remains unaffected; after a refractory period, the process can be repeated

Question 30

What are Holocrine glands

Answer 30

Glands in which there is an accumulation of secretion within the cell cytoplasm; the cells die and are discharged with the secretion contained in them

Question 31

How do endocrine cells store their products

Answer 31

Intracellular storage in the form of intra-cytoplasmic storage granules or by extracellular storage within an intercellular follicle surrounded by secretory cells.

Question 32

What is the function of the basement membrane

Answer 32

* controls spread of disease and infection. * boundary between epithelia (basal lamina), muscle and nerve (external lamina) and connective tissue * condensed layer of ECM * impenetrable barrier but permits the flow of nutrients and metabolises- molecular sieve

Question 33

What is the basement membrane made up of

Answer 33

* heparan sulphate * collagen type IV * fibronectin, laminin, enactin

Question 34

Why is the basement membrane important in the spread of cancer

Answer 34

* is a mechanical barrier | * cancer cells need type IV collagen are and laminin receptors to cross BL

Question 35

5 characteristics of connective tissue

Answer 35

- cells often separated by ECM - contains blood vessels and nerves - cells may communicate - cells often have slow turnover - cells interact with ECM - adhesion molecules

Question 36

What is the function of fibroblasts

Answer 36

Responsible for the synthesis and maintenance of ECM

Question 37

What are the 5 different types of connective tissue

Answer 37

-mesenchyme - embryonic Loose- areolar connective tissue eg around the outside of the GI tract, respiratory and urinary - dense - mechanical support (irregular eg in dermis of skin, regular eg tendon) - reticular- around liver and lymphoid tissue Adipose

Question 38

How is cartilage and bone adapted to their function

Answer 38

Can withstand compression forces and weight bear due to combination of fibres and complexes of proteins and glycosaminoglycans in the ECM

Question 39

What are the components of the ECM of cartilage

Answer 39

- ground substance : GAGs, large proteoglycans complexed with collagen fibres - fibres: type II collagen (hyaline cartilage), type 11 + 1 collagen (fibrocartilage), type II collagen + elastic fibres (elastic cartilage ) - cells : chondroblasts (from pericondrium) - secrete matrix, chondrocytes (maintain matrix)

Question 40

Explain the growth and maintenance of the cartilage

Answer 40

The matrix is permeable to water and so dissolves oxygen and nutrients are delivered this way and waste products can be removed. Cartilage is mainly non vascular so relies on diffusion via extracellular fluid Grows by interstitial as well as a-positional growth

Question 41

What are the 3 different types of cartilage

Answer 41

Hyaline - most common- articulations surfaces, tracheal rings etc Fibrocartilage- intervertebral discs, pubic symphysis Elastic cartilage - external ear, auditory canal, epiglottis etc

Question 42

What are the causes of cartilage problems / diseases

Answer 42

1) genetic factors eg mutations in type II collagen 2) other disorders eg arthritis 3) osteoarthritis results from breakdown of cartilage 4) tears and injuries such as sports injuries

Question 43

How do cells maintain their shape

Answer 43

Actin microfilaments - polar, double stranded, helical array of G actin, 7nm diameter Microtubules dimers of a and B Tubulin arranged as hollow cylinders 25nm, require microtubule organising centre (MTOC) for assembly Intermediate filaments rope-like twisted fibres of various proteins, 10nm