Functional Histology - how normal human tissue structure is adapted to function.

Question 1

What is histology?

Answer 1

Histology means the study of tissue and a tissue is a collection of structurally and functionally similar cells.

Question 2

What is gastrulation?

Answer 2

This is the formation of 3 germ cell layers in the embryo - ectoderm, mesoderm and endoderm.

Question 3

List some examples of mature tissues which derive from ectoderm

Answer 3

Skin, nerves, eyes and ears, adrenal, medulla and pituitary gland.

Question 4

List some examples of mature tissues which derive from mesoderm

Answer 4

Muscle, bone + cartilage, heart + blood vessels, the urogenital system, bone marrow, the lymphatic system and the adrenal cortex.

Question 5

List some examples of mature tissues which derive from endoderm

Answer 5

Lining of the gastrointestinal (GI) and respiratory tracts, GI organs (liver + pancreas), larynx, trachea, lungs, thyroid gland, parathyroid glands and thymus.

Question 6

What epithelium covers the skin?

Answer 6

Stratified squamous keratinising epithelium forms the epidermis of the skin.

Question 7

What happens to the surface keratin layer of the skin in psoriasis?

Answer 7

In psoriasis there is an increased rate of epidermal turnover and this causes the keratin layer to get thickened. Normal keratin has a basket-weave pattern with no nuclei visible but in psoriasis this basket weave is lost, the keratin layer is thickened and nuclei are retained in this layer because the keratinocytes do not have time to fully mature.

Question 8

Which structures provide strong adhesion between keratinocytes in the epidermis?

Answer 8

Desmosomes.

Question 9

What disease is caused by antibodies attacking desmosomes?

Answer 9

Pemphigus vulgaris.

Question 10

What do you call a malignant tumour which derives from the epidermis of the skin (a malignant tumour of squamous epithelium) and how can you identify this?

Answer 10

A malignant tumour of squamous epithelium is squamous cell carcinoma and you can recognise a squamous cell carcinoma because it produces keratin and because you can identify desmosomes between the malignant cells.

Question 11

Which cell produces myelin and speeds up peripheral nerve conduction?

Answer 11

Schwann cell. The schwann cell wraps its cytoplasm around the axon of a nerve insulating it and speeding up nerve conduction. A schwann cell has a wavy spindle shaped nucleus.

Question 12

List 6 functions of epithelial cells.

Answer 12

1. Protection.
2. Absorption.
3. Surface transport.
4. Secretion.
5. Excretion.
6. Gas exchange.

Question 13

List the 4 simple epithelial types and give 1 example of where you might find each type.

Answer 13

1. Simple squamous epithelium eg. mesothelium covering the lungs.
2. Simple cuboidal epithelium eg. lining the renal (kidney) tubules.
3. Simple columnar epithelium eg. epithelial lining of the stomach.
4. Pseudostratified columnar epithelium eg. lining of the bronchi.

Question 14

The most important stratified epithelial types are stratified squamous epithelium which may be keratinised or non-keratinised and transitional epithelium. Give one example of where you might find each of these in the body.

Answer 14

1. Keratinised stratified squamous epithelium eg. epidermis of the skin.
2. Stratified squamous non-keratinising epithelium eg. cervix and oral mucosa.
3. Transitional epithelium eg. bladder, ureters and renal pelvis.

Question 15

What is the main function of transitional epithelium?

Answer 15

Transitional epithelium allows the ureters and bladder to stretch.

Question 16

List the important connective tissues and muscle types.

Answer 16

The connective tissues include adipose tissue, fibrous tissue (such as dermis, tendons, ligaments), cartilage, bone and haemopoietic tissue (blood, bone marrow).

The muscles include cardiac, skeletal and smooth muscle.

Question 17

If you have a bacterial infection which white blood cell would be raised on a full blood count?

Answer 17

Neutrophils. A raised neutrophil count is usually seen with bacterial infections.

Question 18

If you have asthma which white blood cells would be found in the bronchial lining?

Answer 18

Eosinophils.

Question 19

What is the term used to describe a rounded aggregate of activated macrophages/giant cells?

Answer 19

A granuloma.

Question 20

Which cell is the bodies main producer of antibodies?

Answer 20

The plasma cell.

Question 21

List the 4 mucosal types lining the gastrointestinal tract and give an example of each.

Answer 21

The 4 basic mucosal types which are found lining the GIT can be classified as being:

1. Protective (eg. stratified squamous epithelium of the mouth and oesophagus).
2. Secretory (eg. acid secreting glands lining the stomach).
3. Absorptive (columnar cells with surface microvilli lining the small intestine).
4. Mixed absorptive/protective (columnar cells lining the glands of the large bowel).