Building tissues from cells

Question 1

Describe what a tissue is ?

Answer 1

Collections of similar cells and the material surrounding them-
its classification is based on structure of cells, composition of extracellular matrix, functions of the cells of that particular tissue

Question 2

Name four types of tissue

Answer 2

epithelial
connective
muscle
nervous

Question 3

Describe epithelia tissue

Answer 3

exist as sheets

they line the body surface (epidermis )
they line almost all internal cavities
they rest on the basement membrane

depends on diffusion for nutrients- blood vessels never pass through epithelium- always beneath epithelium usually connective tissue

Question 4

Describe the basement membrane

Answer 4

it is extracellular matrix- DENSE- it contains the largest proteins in the body which cross link with each other to form a mesh work.
Epithelia cells attach themselves to the basement membrane by specialised function.

NB if tumours are to come me static they have to penetrate basement membrane

Question 5

How are epithelial cells classified

Answer 5

Cell Shape
Layer Structure
Surface Specialisation
Location and Function

Question 6

Name the different types of shapes

Answer 6

squamous
cuboidal
columnar

Question 7

Name the different layer structure

Answer 7

Simple
Pseudostratified
stratified

Question 8

Name the different surface specialisations

Answer 8

Cilated
Brush Borders
Keratanized

Question 9

Name the different location and functions

Answer 9

eg. respiratory, transitional

Question 10

How do glands originate?

Answer 10

Almost all originate from imaginations of epethilium- hence why they retain the epithelial organisation

Question 11

Name the two types of epithelial glands

Answer 11

Exocrine- secrete to free surface eg. sweat glands

Endocrine- secrete to blood stream

Question 12

How do exocrine glands form?

Answer 12

1) the solid mass of epithelial remain attached
2) These cells then become specialised into secretory cells and excretory ducts
There can be different types of glands eg different number/types of branches and coils

EPITHELIAL CELLS NEVER BREAK THROUGH BASAL LAMINA

Question 13

How do endocrine glands form?

Answer 13

1) the solid mass of epithelial cells detach off
2) These then become specialised into cords of glandular cells.
Immature cells send signals to bring capillaries towards it

EPITHILIAL CELLS NEVER BREAK THROUGH BASAL LAMINA

Question 14

Name the three types of mechanisms of exocrine secretion

Answer 14

Merocrine
Apocrine
Holocrine

Question 15

Merocrine

Answer 15

Vesicles open onto the surface of the cell and the secretory product is discharged from the cell - ie normal exocytosis

Question 16

Aprocrine

Answer 16

Part of the apical (top half of the cell) cytoplasm of the cell break up- larger vesicles
the cell then regrows that part

eg. sweat glands, memory glands, prostate gland

Question 17

Holocrine

Answer 17

The breakdown and discharge of entire secretory cell

eg. sebaceous glands of the skin

Question 18

What is the role of junctions

Answer 18

Keeps epithelial sheets tightly bound

Allows for the remaining of functional integrity of cells’ selective barriers/communication

Question 19

What are are the three types of anchoring junctions?

Answer 19

desmosome
hemidesomosome
adherens

Question 20

Describe the desmosome

Answer 20

Strongest type of junction- connects to adjacent cells

the junctions are linked by Intermediary filaments

facilitates the bending of cell sheets

Question 21

Describe the hemidesmosome

Answer 21

Like the desmosome-the junctions are linked by Intermediary filaments

connects the base of the epithelia cell to the basement membrane-

facilitates the bending of cell sheets

Question 22

Describe Desmonal Proteins

Answer 22

There are two types- desmoglein and desmocolin. Both of these are attached to the IF

the desmogelin of one cell binds homophilically to the desmogelin of the adjacent cell- this promotes adhesion

The strength is emphasised by the fact that the linker proteins do cluster firming a mesh- dense

Question 23

Describe the Adherens junction

Answer 23

It maintains the shape of the cell.
Cadherin dimers of one cell binds homophillically with partner of the neighbouring cel
These dimers are linked by actin filaments which are rigid and stretch across the cell from adherens junction to adherent junction

eg. columnar epitheliar cells

Question 24

Name the two types of non-anchoring proteins

Answer 24

Tight and Gap

Question 25

Tight-

Answer 25

prevents the exchange of material from passing between 2 cells- acts as a seal to the inter membrane space

Brings the plasma membranes of the 2 adjacent cells so close that nothing can fit through them- NO GLUCOSE/NO AA/NO IONS

eg upper part of the digestive track has higher glucose so it diffuses into the epethilal cells but you don’t want movement of water out of the epithelial cells

NB the seal can be relaxed thanks to cell signalling

the two proteins involved are Claudin and occulin which bind to their respective opposite proteins on the adjacent cell

Question 26

Gap

Answer 26

very small small bridges between cytoplasm allowing exchange of materials between cytoplasm of neighbouring cells-

composed of 6 connexins to form a connexon. The hole in the middle is continuous. Allows small molecules to pass through this hole.

This helps calibration of molecules along cells despite the relative position of the cell compared to blood vessel

Question 27

What happens if the conexins are not aligned

Answer 27

the channel is closed