Tissue Level Organisation

Question 1

Define overall function of cell junctions. (2 points)

Answer 1

• Points of contact between adject cells
• Join cells to form tissues

Cell junctions are points of contact between adjacent cell membranes, they join cells together
to form tissues.

Question 2

List THREE (3) types of cell junctions.

Hint - TRY ASKING DIFFERENT GROUPS for HELP

Answer 2

T - Tight
A - Adherns 
D - Desmosomes 
G - Gaps
H - Hemidesmosomes

Question 3

For each of the cell junctions, describe the associated structure

Answer 3

Tight - Plasma membranes fused with transmembrane proteins that seal between the two cells.

Adherns - Contain plaques, actin and cadherins which connect the adjacent cells.

Desmosomes - Contains plaque and cadherins and attaches to keratin

Gaps - Neighbouring cells are connected by fluid filled tunnels called Connexons

Hemidesmosomes - Half a desmosome; same structure as desmosome but it connects cell to the underlying basement membrane and extracellular material using integrin

Question 4

For each of the cell junctions, describe the associated function

Answer 4

Tight - forms watertight seal between cells

Adherns - holds epithelial cells together

Desmosomes - cell to cell stability

Gaps - Cell communication, diffusion of ions and small molecules, transfer of nutrients

Hemidesmosomes - Cell to basement membrane stability

Question 5

List and describe TWO (2) general functions of epithelial tissue.

Answer 5

1. Selective barrier: It helps the transfer of substances in and out of the body.
2. Secretory surface: It releases molecules produced by the cells into the free surface.
3. Protective surface: It resists any abrasive influence of the environment. T

Question 6

Name any TWO (2) covering and lining epithelial tissue types.

Answer 6

Simple Squamous Epithelium
Simple Cuboidal Epithelium
Simple Columnar Epithelium
Pseudostratified Columnar Epithelium
Stratified Squamous Epithelium
Stratified Cuboidal Epithelium
Stratified Columnar Epithelium
Transitional Epithelium

Question 7

Name the two types of epitherial tissue

Answer 7

1. Covering and lining epithelium, such as the epidermis of the skin, lining of blood vessels, ducts, respiratory, reproductive, urinary and gastrointestinal tract.
2. Glandular epithelium, such as the secreting portion of glands (thyroid, adrenal, and sweat glands).

Question 8

List the three (3) Covering and lining epithelium cell arrangments

Answer 8

1. Simple - one cell layer thick.
2. Stratified - two or more cell layers thick.
3. Pseudostratified - all of the cells contact the basement membrane, but not all of them reach the apical surface.

Question 9

List the four (4) Covering and lining epithelium cell shape

Answer 9

1. Squamous - flat.
2. Cuboidal - cube-shaped.
3. Columnar - tall column.
4. Transitional - shape varies with tissue stretching