Basic skin biology Flashcards
What are the functions of the skin?
- Protective barrier against environmental insults
- Temperature regulation
- Sensation
- Vitamin D synthesis
- Immunosurveillance
- Cosmesis
What is erythroderma?
- Arises as a complication of many skin conditions
- Total skin failure
- Can present as an extensive erythematous exfoliative rash
- Emergency presentation
What are the effects of erythroderma?
- 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)
What are the causes of erythroderma?
- Psoriasis
- Eczema
- Drugs
- Cutaneous T cell lymphoma
What are the symptoms of erythroderma?
- Pruritus and discomfort
- Fatigue
- Anorexia
- Feeling cold
What are the signs of erythroderma?
- > 90% of body surface area affected
- Erythematous
- Exfoliative
- Thickened
- Inflamed
- Scaly
- No sparing
What are the four cell types of the epidermis?
- Keratinocytes
- Langerhans cells
- Melanocytes
- Merkel cells
What is the function of keratinocytes?
- Protective barrier
What is the function of Langerhans cells?
- Antigen presenting cells
What is the function of melanocytes?
- Produce melanin
- Provides pigment to the skin
- Protects cell nuclei from UV DNA damage
What is the function of Merkel cells?
- Contain specialised nerve endings for sensation
What are the layers of the epidermis?
- Stratum corneum - horny layer, most superficial
- (stratum lucidum)
- Stratum granulosum
- Stratum spinosum
- Stratum basale - basal layer
What does each layer of epidermis represent?
- A different stage of keratinocyte maturation
- Average epidermal turnover time is about 30 days
What may pathology of the epidermis cause?
- Change in epidermal turnover
- Change in surface of skin
- Change in skin pigmentation
What is the dermis composed of?
- Collagen
- Elastin
- Glycosaminoglycans
What is the function of the dermis?
- Provides strength and elasticity to skin
- Also contains immune cells, nerve cells, skin appendages, lymphatics and blood vessels
What is the function of the sebaceous glands?
- Produce sebum through hair follicles
- Secrete sebum onto skin for lubrication
- Active after puberty
- Stimulated by conversion of androgen to dihydrotestosterone
What causses acne vulgaris?
- Increased sebum production and bacterial colonisation
What are the functions of eccrine and apocrine glands?
- Regulate body temperature
- Innervated by sympathetic system
What is the difference between eccrine and apocrine glands?
- Eccrine glands are widespread
- Apocrine glands are active following puberty and are found in axillae, areolae, genitalia and anus
What does each hair consist of?
- Modified keratin
- Divided into hair shaft and hair bulb
What are the 3 main types of hair?
- Lanugo hair (soft hair all over body)
- Vellum hair (soft hair all over body)
- Terminal hair (coarse long hair)
What is the growth cycle of hair follicles?
- Anagen
- Catagen
- Telogen
- Disruption of this cycle can lead to hair loss
Outline the structure of nails
- Consists of a nail plate which arises from nail matrix at posterior nail fold and rests on nail bed
- Nail bed contains blood capillaries to nourish nail
Why is it important to examine a patient’ nails?
- Can be a guide to other systemic problems
- Deficiencies and lung cancers
- Chronic skin conditions can cause thickening/disruption of nail bed and separation of nail from nail bed
