Epithelia

Question 1

Which type of epithelium comes from each embryonic germ layer?

Answer 1

Ectoderm - exterior surfaces - skin and eye cornea
Mesoderm - urinary system and pericardial/pleural sacs
Endoderm - Respiratory, liver, GI and glands

Question 2

What are the key properties of the basement membrane?

Answer 2

It is a thin, flexible, acellular layer which lies between the epithelia and the connective tissue. It is laid down by epithelia cells and serves as a molecular filter.

Question 3

What is the relationship between malignant cells and the basement membrane?

Answer 3

If malignant cells have penetrated the basement membrane then there is a much poorer prognosis.

Question 4

Where is simple squamous epithelia found?

Answer 4

Lines lumen of arterioles, venules and lymphatic vessels and is termed endothelium here. It also lines pleural sac/ pericardium/ peritoneum and here it is termed mesothelium.

Question 5

How does the function of simple squamous epithelia link to its structure?

Answer 5

Simple squamous epithelia is a single felled sheet of cells which is very thin and therefore perfect for gas exchange and osmosis/ diffusion. This is why it is found in the alveoli, kidney and also in blood/ lymphatic vessels.

Question 6

Lost four places simple cuboidal epithelia can be found.

Answer 6

Thyroid follicles - hormone synthesis, storage & metabolism
Ducts of exocrine glands (pancreas) absorption and conduit
Kidney tubules - absorption and secretion
Ovary surface - barrier/ covering

Question 7

Name two attachments simple columnar epithelia can have.

Answer 7

Cilia (in Fallopian tube)
Micro villi (GI to increase SA)

Question 8

What are the functions of simple columnar epithelia?

Answer 8

Absorption - small intestine and colon
Secretion - small intestine and gastric glands
Lubrication- small intestine and colon
Transport - in Fallopian tubes.

Question 9

Why are simple columnar epithelia found in the gall bladder?

Answer 9

It reabsorbs water from the bile which reduces the volume before it enters to intestine.

Question 10

Explain what the junctional complex is in simple columnar epithelia.

Answer 10

This is where occludin binds plasma membranes of adjacent cells to prevent molecules slipping between them. His means that certain proteins can be restricted to the apical surface. Cholera toxins affect this and that is why infection occurs.

Question 11

What can be said about all cells in Pseudostratified epithelia?

Answer 11

They are all in contact with the basement membrane

Question 12

What type of epithelia is found in the upper respiratory tract?

Answer 12

Ciliated Pseudostratified epithelia.

In the URI particles are immobilised in the mucus secreted by goblet cells and then moved up where they are swallowed.

Question 13

Where is pseudostratified epithelium found?

Answer 13

Upper respiratory tract, epididymis (duct behind the testis) and ductus deferens, lacrimal (tear) sac, large excretory ducts, auditory tube and parts of the lymphatic cavity.

Question 14

Stratified squamous epithelia is found in the vagina and it rich in glycogen. Why?

Answer 14

Lactobacilli ferment sugars which produces lactic acid and maintains a low pH.

Question 15

Why is stratified squamous epithelia found in the oesophagus?

Answer 15

To protect from abrasion.

Question 16

What type of epithelium is the skin?

Answer 16

Keratinised simple squamous epithelia. It protects against abrasion and trauma and also shields us from UV damage. It prevents water loss and ingress of microbes. The only other place it is found is in parts of the oral cavity.

Question 17

State the location and function of transitional epithelia.

Answer 17

It is found predominantly in the Urinary system. It has two different shapes when it is relaxed and stretched but this allows the size of the bladder to increase depending on urine quantity. It is also found in the ureters.

Question 18

What is the one thing which can increase the rate of epithelium renewal?

Answer 18

Injury triggers replacement of cells which have been lost.

Question 19

What two things affect the renewal rate of epithelia?

Answer 19

Location and function.

Skin is sloughed off every 28 days and replaced whilst in the small intestine cells are replaced every 4-6 days.

Question 20

What is metaplasia?

Answer 20

This is where epithelium type changes

For example epithelium of the RT changing from pseudostratified to simple squamous in heavy smokers. It is reversible.

Question 21

What is the term for when a change in epithelium causes a tumour to form which can be benign and similar to the original tissue type or malignant with altered cell structure which can invade neighbouring cells?

Answer 21

Neoplasia

Question 22

What is epithelium?

Answer 22

Sheets of contiguous cells, of varied embryonic origin which cover external surfaces of the body and line internal surfaces.

Question 23

By which cells are compound epithelia classified?

Answer 23

They are classified by the most superficial layer of cells. Only the most basal cells are in contact with the basement membrane in this type of epithelium.