Skin

Question 1

What are the functions of skin?

Answer 1

Barrier to infection
Thermoregulation
Protection against UV
Protection against trauma
Vitamin D synthesis

Question 2

Give the three basic layers of skin.

Answer 2

1. Epidermis
2. Dermis
3. Subcutaneous tissue

Question 3

What is the outermost layer of the epidermis called?

Answer 3

Stratum corneum

Question 4

Corneo-desmosomes make up the stratum corneum. What do they do?

Answer 4

They are adhesion molecules. They keep corneocytes together.

Question 5

Which disease causes increased numbers of corneo-desmosomes?

Answer 5

Psoriasis. Thickening of stratum corneum.

Question 6

Which disease causes decreased numbers of corneodesmosomes?

Answer 6

Atopic eczema. Thinning of stratum corneum. Increased risk of inflammation.

Question 7

Which substance fills corneocytes?

Answer 7

NMF - natural moisturising factor. Keeps H2O inside skin to maintain hydration.

Question 8

Which protein produces NMF?

Answer 8

Filaggrin, derived from profilaggrin

Question 9

Which process involves the degradation of mature corneo-desmosomes under the action of proteases?

Answer 9

Desquamation

Question 10

What is the PH of normal skin?

Answer 10

5.5

Question 11

Briefly describe the brick wall model.

Answer 11

Bricks: Corneocytes
Iron rods: Corneo-desmosomes
Cement: Lipid lamellae

Question 12

What is the role of Vitamin D in the skin?

Answer 12

Produces anti-microbial peptides to defend skin from pathogens.

Question 13

What causes inflammation of the skin?

Answer 13

Allergens. Penetrate skin, met by lymphocytes which release chemicals causing flare ups.

Question 14

What are the types and causes of skin inflammation?

Answer 14

Red skin: Dilation of blood vessels, due to lymphocyte activity
Itchy skin: Stimulation of nerves
Dry skin: Skin cells leaking, due to lymphocyte activity

Question 15

What happens if skin PH is increased?

Answer 15

Corneo-desmosomes become damaged. Results in breakdown of skin barrier, increasing risk of infection.

Question 16

What causes an increase in skin PH?

Answer 16

Lack of NMF (absence of filaggrin), meaning there is less water retention in corneocytes.

Question 17

Briefly outline the steps of acne formation.

Answer 17

1. Hypercornification of stratum corneum - leads to corneo-desmosomes blocking the entrance to hair follicles
2. Results in increased production of sebum by sebaceous glands
3. Sebum is trapped in narrowed hair follicle
4. Sebum stagnates due to no oxygen
5. Anaerobic conditions allow propionic bacteria acnes to multiply
6. p.acnes break down sebum causing irritation and inflammation
7. chemicals released by p.acnes attract neutrophils resulting in pus formation