L3- Integrating cells into tissues and organs

Question 1

a) When do cells first coalesce? (stick together)

b) Where do all cells come from

Answer 1

a) During embryogenesis

b) Epiblast

Question 2

What is the primary cell of the connective tissue?

Answer 2

Mesenchymal stem cell (a type of immature fibroblast)

Question 3

Connective tissue:

a) Structure
b) Functions

Answer 3

a) Made up of 3 components:
- cells: mature fibroblasts/fibrocytes, fixed adipocytes, reticular cells
- Fibres: collagen, elastin, reticular fibres
- Ground substance: glucosaminoglycans e.g. hyaluronic acid

b) - Binding and supporting (holding skin, gut, lungs etc together)
- protecting (bone protecting vital organs)
- insulating (fat underlying skin)
- Storing reserve fuel and cells (bone marrow and fat tissue)
- transporting subtances within body (blood and interstitium)
- seperation of tissues

Question 4

a) Where in the body are epithelial cells found?

b) What is found near epithelial tissue?

Answer 4

a) line all the cavities and free surfaces of the body
b) - specialised junctions between epithelial cells make tissue barriers
- almost always rest on supporting bed of connective tissue (through basement memb)
- supporting bed attaches epithelial layer to other tissues such as muscle

Question 5

What are the epithelial cell adherence systems found in:

a) the lateral surface
b) the basal surface

Answer 5

a)
- Tight junctions
- Adherens junctions
- desmosomes
- gap junctions
- cell adhesion molecules

b) - Hemi-desmosome
- focal adhesions
- integrins
- proteoglycans
- cell adhesion molecules

Question 6

Tight junctions:

a) Where are they found
b) Function/role

Answer 6

a) Very top of the cell nearest to the lumen/apical surface in lateral border
b) To prevent movement of larger molecules through the outerlayer/lumen into the deeper tissue layers of the organ

Question 7

Adhesion junctions:

a) Where are they found?
b) Function/role

Answer 7

a) 1/3 distance from luminal surface in lateral surface in pairs
b) Linked to E-cadherin proteins: sometimes called adhesion belt
- tissue stabilising factor and additional transport barrier

Question 8

Desmosomes:

a) Where are they found?
b) Function/role

Answer 8

a) 1/3 between top and bottom of cells
- found in tissues that experience intense mechanical stress (cardiac muscle, epithelia, bladder)

b) - provide mechanical strength and prevent tissue destruction

Question 9

Gap junctions:

a) Where are they found?
b) Function/role

Answer 9

a)