Lecture 6- Skin biology Flashcards
Functions of the skin
- Protective against environmental insults
- Temp regulation
- Sensation
- Vit D synthesis
- Immunosurveillance
- Cosmesis
three main layers of the skin
Epidermis, dermis and hypodermis
Epidermis
- 4 major cell types- each with individual function
- Keratinocytes- protective barrier
- Langerhans- APCs
- Melanocytes- produce melanin which provides pigment to the skin and protects cell nuclei from UV DNA damage
- Merkel cells- contain specialised nerve endings for sensation
layers of the epidermis
“Come Lets Get Some Beers”
- Each layer represents a different stage of maturation of keratinocytes
- Stratum Basale
- Stratum spinosum
- Stratum granulosum
- Stratum corneum
Extra layer = stratum
extra layer of epidermis found in areas of thicker skin e.g. palms and soles
stratum lucidum
Average epidermal turnover=
30 days
- Some conditions have much higher turnover = psoriasis
pathology of the epidermis may cause
- change in epidermal turnover
- change in surface of the skin
- changes in pigmentation of the skin
epidermal pathology examples
- stable plaque psoriasis
- vitiligo
Stable plaque psoriasis
Typically found on torso, back of leg, extensor surfaces
Vitiligo
- Autoimmne condition leading to depigmentation
- Hypopigmentation (partial loss) or depigmentation (complete loss of pigmentation)
function of the dermis
- The cushion
- Composed of collagen, elastin and glycosaminoglycans
- Provides strength and elasticity
what does the dermis contain
- Immune cells
- Nerve cells
- Skin appendages
- Lymphatics
- Blood vessels
- hair
- glands
- sebaceious
- eccrine and apocrine (found at the border of the hypo and dermis)
Sebaceous glands
- Produce sebum through hair follicles (pilosebaceous unit)
- Secretes 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 vulgaris
sweat glands
- Sweat glands
- Regulate body temp
- Innervated by sympathetic system
- Two types: eccrine and apocrine
eccrine sweat glands are found
widespread
apocrine sweat glands are found
Apocrine are active following puberty and found in axillae, areolae, genitalia and anus
hair
- Each hair consists of modified keratin and is divided into hair shaft and bulb
3 types of hair
Terminal hair.
Vellus hair.
Lanugo hair.
Each hair follicle enters a growth cycle which has 3 main phases
- Anagen
- Catagen
- Telogen
Dermal pathology
Dermatographia
Wheal- Urticarial rash
Dermatographia
- If you run your finger along skin or slight scratch you get raised bumpy skin
- Caused by dermal oedema (swelling of the dermal layer)
- Why does it happen?
- Rapid and massive release of histamine
Wheal- Urticarial rash
- Raised itchy rash that appear on the skin
- Allergic reaction
describe alopecia areata
patchy hair loss
male pattern bolding
High levels of androgens in the body produce a hormone called Dihydrotestosterone (DHT). DHT binds to certain proteins in the body, which in turn reduces the size of your hair follicles. This may result in thinning of the hair and may even delay the growth of new hair strands
nail anatomy
- 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
Chronic fungal nail infection or psoriasis etc
what is this
Subungual melanoma
If you see a rash on one part of the body always
look around the rest of the body
describe this presentation
- Extensive
- Erythematous
- Non- sparing (high coverage)
What is the name of this clinical presentation?
- Erythroderma
- ‘Total skin failure’
Erythroderma– at risk of:
- Hypothermia
- Loss of thermoregulation
- Infection
- Loss of protective barrier
- Renal failure
- Insensible losses
- High output cardia failure
- Peripheral vasodilation
- Protein malnutrition
- scaly appearance of skin- high turnover of skin
Causes of erythroderma (90% of body surface affected)
- psoriasis
- eczema
- drugs
- cutaneous cell lymphoma
symptoms of erythroderma
- pruritus
- fatigue
- anorexia
- feeling cold
signs of erythroderma
- erythematous
- thickened
- inflamed
- scaly
- non-sparing
