9. Structure, Function and Disorder of Skin

Question 1

How can disease affect the macroscopic variations of colour, hair and wrinkling of skin?

Answer 1

Colour - vitiligo (autoimmune depigmentation)
Hair - alopecia areata (autoimmune hair loss)
Wrinkling - uv-induced abnormalities (sun burn, skin ageing, skin cancers).

Question 2

What is the stratum corneum made of?

Answer 2

Dead squamous epithelia that will flake off.

Question 3

What are the five layers of skin?

Answer 3

Stratum corneum (horny layer), granular layer, prickle cell layer, basal layer and dermis.

Question 4

What are keratins?

Answer 4

Heterodimeric fibrous proteins which contribute to the strength of the epidermis. They’re the main constituents of hair and nail.

Question 5

What cells in the skin undergo mitosis?

Answer 5

Keratinocytes, their daughter cells move upwards and have terminal differentiation so lose the ability to divide.

Question 6

What makes up the granular layer of the epidermis?

Answer 6

Keratohyalin granules. Keratins, fibrous proteins and enzymes.

Question 7

What is the horny layer/ stratum corneum made up of?

Answer 7

Layers of flattened corneocytes.

Question 8

What is the transit time of keratinocytes from basal layer to stratum corneum?

Answer 8

30-40 days.

Question 9

What are melanocytes and langerhan cells? (Their origin, where they’re found, how they’re seen, what their function is).

Answer 9

Dendritic cells, melanocytes of neural crest origin and langerhan cells of bone marrow origin. Both cant be seen histologically without special stains. Melanocytes are in the basal layer of the epidermis and produce melanin that give the skin colour, the more melanin produced, the more tanned the skin. Langerhan cells are scattered through the prickle cell layer and present antigens to T lymphocytes so are involved in the immune response.

Question 10

What stain is needed to view Langerhan cells and melanocytes histologically?

Answer 10

S100 monoclonal antibody staining.

Question 11

What is noticeable about photomicrographs of palmar skin?

Answer 11

The horny layer is really thick and there are no hair follicles. The prickle cell layer is also very thick.

Question 12

What is noticeable about the photomicrograph of scalp skin?

Answer 12

The stratum corneum flakes off as dandruff, there are lots of hair follicles and sebaceous glands.

Question 13

What is psoriasis?

Answer 13

Abnormal epidermal growth and differentiation that affects 2% of the population.

Question 14

What causes psoriasis?

Answer 14

Could be to do with genetics but not known yet. Extreme proliferation of epidermal basal layer and thickening of the prickle cell layer with excess stratum corneum cells (scaling). The cells have a week long cycle rather than 30-40 day cycle.

Question 15

What is a possible treatment of psoriasis?

Answer 15

UV photo therapy.

Question 16

What is allergic contact dermitis mediated by?

Answer 16

Langerhan cells.

Question 17

What is a malignant melanoma?

Answer 17

Malignant growth if melanocytes.

Question 18

What is vitiligo?

Answer 18

Autoimmune destruction of melanocytes.

Question 19

What causes hairs to go grey with age?

Answer 19

Melanocytes not functioning in hair follicles with age.

Question 20

What affects the prognosis of malignant melanoma?

Answer 20

Whether it has gone through the epidermal basement membrane. If it hasn’t, the prognosis is good, if it has, the prognosis is bad.

Question 21

What makes up the extracellular matrix of the dermis?

Answer 21

Collagens, elastin and other extracellular matrix components.

Question 22

What are the components of the dermis?

Answer 22

Blood vessels, lymphatic vessels, mast cell, nerves and extracellular matrix.

Question 23

What are keloids caused by?

Answer 23

Excess scar tissue productions following wounding.

Question 24

How do blood vessels in different layers of the skin differ?

Answer 24

In the superficial dermis, there are smaller blood vessels. In the deeper dermis there are larger blood vessels.

Question 25

What causes the birth defect ‘port wine stain’?

Answer 25

Congenital malformation of dermal blood vessels.

Question 26

What causes allergic reactions?

Answer 26

Histamine released from cytoplasmic granules in mast cells, caused increased vascular permeability and leakage of plasma into exactravascular sites causing oedema.

Question 27

What causes acne?

Answer 27

Sebaceous glands getting obstructed, increased serum production and infection.

Question 28

What is hyperhidrosis?

Answer 28

Increased swearing especially on the palms and soles.

Question 29

What are apocrine sweat glands?

Answer 29

Large sweat glands abundant in axial law, genital and submammary areas.

Question 30

What are the four major function of the skin?

Answer 30

Barrier, sensation, thermoregulation and psychosexual communication.

Question 31

How does the skin act as a barrier?

Answer 31

The outer epidermis prevents per cutaneous absorption of exogenous substances. It can be overcome during percutaneous absorption of drugs or in some diseases.

Question 32

What does poor barrier function of the skin lead to?

Answer 32

Loss of fluid, protein, other nutrients and heat. Also excessive absorption of exogenous agents like drugs.

Question 33

What causes loss of the sensation function of the skin?

Answer 33

Leprosy and diabetic sensory neuropathy.

Question 34

How does the skin act as a thermoregulator?

Answer 34

Vascular thermoregulation (dilation of skin blood vessels leads to heat loss and constriction leads to heat gain) and thermoregulatory eccrine sweating (evaporation of eccrine sweat causes cooling).

Question 35

How can skin vary macroscopically?

Answer 35

In colour, hair, laxity/wrinkling.