Dermatology

Question 1

Functions of skin

Answer 1

1. Protective barrier against environmental insults
2. Temperature regulation
3. Sensation
4. Vitamin D synthesis
5. Immunosurveillance
6. Appearance/cosmesis

Question 2

Skin appendages (4)

Answer 2

1. Hair
2. Nails
3. Sebaceous glands
4. Sweat glands

Question 3

4 major cell types in epidermis and their roles

Answer 3

1. Keratinocytes -produce keratin as a protective barrier
2. Langerhan’s cells - present antigens and activate T-lymphocytes for immune protection
3. Melanocytes - produce melanin, which gives pigment to the skin and protects cell nuclei from UV radiation-induced DNA damage
4. Merkel cells - contain specialised nerve endings for sensation

Question 4

4 skin layers and composition

Answer 4

1. Stratum basale (basal cell layer) - actively dividing cells, deepest layer
2. Stratum spinosum (prickle cell layer) - differentiating cells
3. Stratum granulosum (granular cell layer) - cells lose their nuclei and contain granules of keratohyaline, Secrete lipid into the intercellular spaces
4. Stratum corneum (horny layer) - layer of keratin, most superficial layer

Question 5

What extra skin layer might you find on the sole of the foot?

Answer 5

Stratum lucidum - beneath the stratum corneum. Consists of paler, compact keratin.

Question 6

Pathology of the epidermis

Answer 6

1. Changes in epidermal turnover time, e.g. psoriasis = reduced
2. Changes to surface of skin or loss of epidermis, e.g. scales, crusting, exudate, ulcer
3. Changes in pigmentation (hypo or hyper)

Question 7

What is the dermis made up of?

Answer 7

• Primarily collagen
• Elastin
• Glycosaminoglycans (synthesised by fibroblasts)

Also contains:

• Immune cells
• Nerves
• Skin appendages
• Lymphatics
• Blood vessels

Question 8

Pathology of the dermis

Answer 8

1. Changes in contour of skin or loss of dermis, e.g. papules, nodules, skin atrophy
2. Disorders of skn appendages, e.g. hair, acne (sebaceous glands)
3. Changes related to lymphatic and blood vessels

Question 9

List some outcomes of changes to lymphatic and blood vessels in dermis

Answer 9

• Erythema (vasodilation)
• Urticaria (increased permeability of capillaries and small vessels)
• Purpura (capillary leakage)

Question 10

3 types of hair

Answer 10

• Lanugo hair (fine long hair in fetus)
• Vellus hair (fine short hair on all body surfaces)
• Terminal hair (coarse long hair on scalp, eyebrows, eyelashes, pubic areas)

Question 11

What does a single hair consist of

Answer 11

• Modified keratin

Divided into:

• Hair shaft (keratinised tube)
• Hair bulb (actively dividing cells and melanocytes)

Question 12

Hair growth cycle

Answer 12

1. Anagen (long growing phase)
2. Catagen (short regressing phase)
3. Telogen (resting/shredding phase)

Question 13

Hair pathology

Answer 13

1. Reduced or absent melanin pigment production (grey/white hair)
2. Changes in duration of growth cycles, e.g. hair loss = premature entry of hair follicles into telogen phase
3. Shaft abnormalities

Question 14

Nail

Made up of?

Answer 14

• Nail plate (hard keratin)
• Arises from nail matrix at posterior nail fold
• Nail bed contains blood capillaries

Question 15

Nail pathologies

Answer 15

• Abnormalities of nail matrix (pits and ridges)
• Abnormalities of nail beds (splinter haemorrhages
• Abnormalities of nail plate (discoloured nails, thickening of nails)

Question 16

Sebaceous glands

PHysiology

Answer 16

• Produced sebum via hair follicles
• Secrete sebum onto skin surface to lubricate and waterproof the skin
• Are stimulated by conversion of androgens to dihydrotestosterone (become active during puberty)

Question 17

Pathology of sebaceous glands

Answer 17

• Increased sebum production can leas to bacterial colonisation, e.g. acne
• Sebaceous gland hyperplasia

Question 18

Sweat glands

Physiology

Answer 18

• Regulate body temp

- Innervated by sympathetic nervous system

Question 19

Sweat glands

Two types

Answer 19

1. Eccrine - distributed in the skin
2. Apocrine - found in axillae, aerolae, genitalia, anus and modified glands are found in external auditory canal. Only function from puberty onwards. Bacteria action on sweat causes body odour.

Question 20

Pathology of sweat glands

Answer 20

1. Inflammation/infection of apocrine glands (hidradenitis suppurativa)
2. Overactivity of eccrine glands (hyperhidrosis)

Question 21

Principle of wound healing

4 stages

Answer 21

1. Haemostasis
2. Inflammation
3. Proliferation
4. Remodelling

Question 22

Haemostasis processes

Answer 22

• Vasoconstriction and platelet aggregation

- Clot formation

Question 23

Inflammation processes

Answer 23

• Vasodilation
• Migration of neutrophils and macrophages
• Phagocytosis of cellular debris and invading bacteria

Question 24

Proliferation processes

Answer 24

• Granulation tissue formation (synthesised by fibroblasts) and angiogenesis
• Re-epithelialisation (epidermal cell proliferation and migration)

Question 25

Remodelling processes

Answer 25

- collagen fibre re-organisation | - scar maturation