basic skin biology

Question 1

What are the functions of skin

Answer 1

• Protective barrier against environmental insults
• Temperature regulation
• Sensation
• Vitamin D synthesis
• Immunosurveillance
• Cosmesis

Question 2

What are the complications of erythroderma

Answer 2

• ‘Total skin failure’
• Hypothermia (loss of thermoregulation)
• Infection (loss of protective barrier)
• Renal failure (insensible losses)
• High output cardiac failure (dilated skin vessels)
• Protein malnutrition (high turnover of skin)

Question 3

What are the acuses and effects of eryhtroderma

Answer 3

Erythroderma
•>90% of body surface area affected, erythematous and exfoliatitive
•Causes: psoriasis, eczema, drugs, cutaneous T cell lymphoma
•Symptoms: pruritus, fatigue, anorexia, feeling cold
•Signs: erythematous, thickened, inflamed, scaly, no sparing

Question 4

What are the major cell types in skin

Answer 4

4 major cell types each with individual function
•Keratinocytes -protective barrier
•Langerhancells-antigen presenting cells
•Melanocytes-produce melanin which provides pigment to the skin and protects cell nuclei from UV DNA damage
•Merkel Cells-contain specialisednerve endings for sensation

Question 5

What are the layers of the epidermis

Answer 5

• 4 layers of the epidermis
• Each layer represents a different stage of maturation of the keratinocyte •Average epidermal turnover time is about 30 days
• The 4 layers of the epidermis include: stratum basale(basal layer), stratum spinosum, stratum granulosum, stratum corneum(horny layer-most superficial)
• Stratum lucidumfound in areas of thicker skin such as palms and soles

Question 6

What can pathology of the epidermis cause

Answer 6

•Pathology of the epidermis may cause:•a) Change in epidermal turnover•b) Change in surface of the skin •c) Changes in pigmentationof the skin

Question 7

What is the dermis composed of

Answer 7

• Composed of collagen, elastinand glycosaminoglycans
• Provides strength and elasticity
• Also contains immune cells, nerve cells, skin appendages, lymphatics and blood vessels

Question 8

What is a sebaceous gland

Answer 8

• Produce sebum through hair follicles (pilosebaceous unit)
• Secrete sebum on to skin which lubricates skin•Active after puberty
• Stimulated by conversion of androgen to dihydrotestosterone
• Increased sebum production and bacterial colonisation in conditions such as acne vulagris

Question 9

What are eccrine and apocrine glans

Answer 9

• Regulate body temperature
• Innervated by sympathetic system
• Two types: Eccrine and Apocrine
• Eccrine are widespread
• Apocrine are active following puberty and are found in axillae, areolae, genitalia and anus.

Question 10

What are hairs in the skin and what are the types and how do they grow

Answer 10

• Each hair consists of modified keratin and is divided into hair shaftand hair bulb
• 3 main types of hair: lanugo hair, vellum hair (short hair all over body), terminal hair (coarse long hair)
• Each hair follicle enters a growth cycle which has 3 main phases: anagen, catagen, telogen

Question 11

What are nails cimposed of?

Answer 11

•Consists of a nail plate which arises from the nail matrix at the posterior nail fold and rests on the nail bed.•Nail bed contains blood capillaries