skin physiololgy Flashcards
skin functions
waterproof barrier
physical barrier
UV Barrier
immune organ
3 layers of skin
epidermis
Dermis
Hypodermis
how does skin form a waterproof barrier
tight junctions between cells in stratum granulosum , epidermal lipids form an outside in and inside out barrier
prevents transepidermal water loss
function of the epidermis
water proofing
physical barrier
immune function
UV
Dermis function
thermoregulation
vitamin d synthesis
sensory organ
function of subcutis/ hypodermis layer
thermoregulation
energy reserve
vit d storage
endocrine organ
why does skin wrinkle when wet
mediated by sympathetic nervous system
due to vasoconstriction in dermis
improves grip
how does skin act as a physical barrier
to resist trauma
stratified epithelium helps resist abrasive forces
fat in subcutis acts as a shock absorber
how is the skin an endocrine organ
androgens act on follicles and sebaceous glands
thyroid hormones act on skin
how can UV a and UV b damage skin
burns
photo- aging
supress action of langerhans cells
DNA damage
what does skin colour depend on
melanin
carotenoids
oxy/ deoxyhaeomoglobin
where is melanin synthesised
melanosomes within melanocytes from tyrosine
From stratum granulosa
transported via dendrites
response to immediate pigment darkening process
photooxidation of existing melanin
redistribution of melanosomes
occurs within minutes and lasts hours-days.
how does skin acts as a barrier to infection
large sa to environment
skin as an immune organ
Epidermis:
Langerhans cells- antigen presenting cells
Dermis Regulatory T cells Natural killer cells Dendritic cells Macrophages Mast cells
epidermis as a immune factor
Epidermis
Keratinocytes secrete cytokines and chemokines that maintain populations of leucocytes in skin
Langerhans cells are antigen-presenting cells and secrete cytokines
what does the skin do when challenged
LC migrate to dermis and lymph nodes and activate a T-cell response
Keratinocytes proliferate & secrete cytokines
Leucocytes enter skin from blood
how does skin help to regulate blood flow
insulation- subcutaneous fat
heat loss
eccrine sweating
what is produced from the breakdown of filagrin
NMF- natural moisturising factor which is acidic
how does skin shed
breakdown of corneodesmosomes that link the skin together
what switches off proteases
low ph
5 layers of the epidermis?
Stratum corneum Stratum lucidum Stratum granulosum Stratum spinulosum Stratum basale
what does the corneum contain
dead keratanised cells
what does the lucidum contain
dead cells containing keratohyalin
