L4: Epithelial Tissues

Question 1

What are the main functions of epithelial tissues?

Answer 1

For barrier or lining:

• Protection;
• Absorption;
• Diffusion;
• Secretion.

(PADS)

Question 2

What are the two major types of epithelial tissues?

Answer 2

1. Surface;

2. Glandular.

Question 3

What do surface epithelial tissues do?

Answer 3

Cover or line all body surfaces, tubes and cavities to create boundaries between environments

Question 4

What do glandular epithelial tissues do?

Answer 4

Primarily for secretion, endo and exocrine

Question 5

How are epithelial tissues classified?

Answer 5

3 main criteria:

• Number of layers;
• Shape;
• Adaptations.

Question 6

How can epithelial tissues be layered?

Answer 6

• Simple, 1 layer (for DAS);
• Stratified, 2 or more layers (for P);
• Pseudostratified, 1 layer but looks like more.

Question 7

Why do pseudostratified epithelium, look stratified?

Answer 7

• Nuclei at different heights;

- Different height of apical surface.

Question 8

Why are stratified epithelium good for areas exposed to more stress?

Answer 8

Quick turnover of cells - cells mature from the basal layer by continuous division of stem cells

Question 9

What shapes can epithelial cells be?

Answer 9

• Squamous;
• Cuboidal;
• Columnar;
• Transitional.

Question 10

What adaptations can epithelial cells have and what does this contribute to their function?

Answer 10

• Microvilli - projections, increase SA, good for greater absorption;
• Cilia - long, motile projections that beat rhythmically;
• Keratin - increases mechanical strength of the layer and is good for protection.

Question 11

Where do you find simple squamous epithelial? Provide an example

Answer 11

Line surfaces involved in passive diffusion, e.g. lungs, capillaries.

Question 12

Where do you find simple cuboidal epithelial? Provide an example

Answer 12

Line small ducts and tubules, e.g. collecting tubules in the kidneys, small ducts of salivary glands.

Question 13

Where do you find simple columnar epithelial? Provide an example

Answer 13

Line absorption surfaces, e.g. small intestine (with microvilli).

Question 14

What are goblet cells?

Answer 14

Modified columnar epithelial cells, they synthesise and secrete mucus and are scattered throughout simple columnar epithelium.

Question 15

Where do you find ciliated simple columnar epithelial? Provide an example

Answer 15

Ciliary action facilitates transport of the ovum, ovary to the uterus. E.g. female reproductive tract.

Question 16

Where do you find ciliated pseudostratified columnar epithelial? Provide an example

Answer 16

Cilia propel the mucus at the surface containing trapped particles, e.g. airways of the respiratory system.

Question 17

Where do you find stratified squamous epithelial? Provide an example

Answer 17

Line surfaces of the oral cavity, provide protection against sharpness, hot/ cold, mechanical work.

Non-keratinised: soft mucosal tissues and pharynx.

Keratinised*: gingival tissues.

• epidermis (top layer of skin) too.

Question 18

Where do you find stratified cuboidal epithelial? Provide an example

Answer 18

Ideal for secretory surfaces e.g. secretory ducts of exocrine glands, such as salivary.

Question 19

Where do you find stratified columnar epithelial? Provide an example

Answer 19

E.g. Male urethra and lining of some glands.

Question 20

Where do you find transitional epithelial? Provide an example

Answer 20

Allows for expansion, e.g. the bladder.

Question 21

What differentiates, regarding the structure, non and keratinised epithelium?

Answer 21

Keratinisation is based on the layer at the apical surface of an epithelium

Question 22

What does keratinisation provide?

Answer 22

Enhanced resistance to stress by forming a tough, non-living layer at the surface (epithelial cells accumulate keratin as they mature).

Question 23

At what surface of an epithelium do you find ‘free’ cells?

Answer 23

The apical surface

Question 24

At what surface of an epithelium do you find the basement membrane?

Answer 24

The basal surface

Question 25

How are carcinomas classified?

Answer 25

Based on cells or origin, e.g. squamous cell carcinoma resembles a stratified squamous epithelium.

Question 26

What does the term ‘dysplastic epithelial cells’ mean?

Answer 26

Cells proliferating in an uncontrolled manner, can destroy and invade adjacent cells.