skin physiology and histology Flashcards
what 3 factors make the skin a waterproof barrier?
- keratin
- tight junctions
- lipids
what 3 factors make the skin a physical barrier to trauma?
- tight junctions in keratinocytes to resist frictional forces
- stratified epithelium resists abrasive forces
- fat in subcutis acts as shock absorber
what are the tissue resident macrophages in skin?
langerhans cells
what do langerhans cells do in an immune response?
= antigen presenting macrophages
- migrate from epidermis to dermis
- active a T cell response
what do keratinocytes do in an immune response?
- proliferate
- secrete cytokines
what type of sensation do merkle cells respond to?
light touch
what are the 2 types of mechanoreceptors in the dermis? what sensations do they respond to?
- pacinian corpuscles → pressure/vibration
2. meissner corpuscles → touch
how is the skin an energy store?
subcutaneous fat
- acts as an insulator, shock absorber AND energy storer
white adipose connective tissue
how can UV affect skin?
- burns
- suppress action of langerhans cells
- damage DNA (skin cancer)
which vitamin is produced and stored in the skin? In which layers?
vitamin D
- produced In the superficial layers of the skin + stored In the deeper layers
How is Vitamin D synthesised?
UVB light
cleaves 7-dehydrocholestrol to pre vitamin D3 (cholecalciferol)
Vit D2 from supplements & D3 in diet
hydrolysed in liver into 25-hydroxy vitamin D (ie. calcifediol)
hydrolysed in kidney to 1,25 hydroxy vitamin D (ie. Calcitriol)
how is the skin involved in thermoregulation?
The amount of blood flow to the skin determines the degree of heat loss and, therefore, the core body temperature.
how many layers are there of the skin?
3
epidermis
dermis
subcutaneous tissue (fat)
what is the epidermis?
- the outer layer of skin
- an epithelial layer resting on a BM made of type 4 collagen
what are the 4 layers of the epidermis?
- stratum corneum (outermost)
- stratum lucidum
- stratum granulosum
- stratum spinousum
- stratum basale (innermost)
what are the epidermal adnexae?
- they are specialised down growths of the epidermis into the dermis
give 4 examples of epidermal adnexae structures?
- hair follicles
- sebaceous glands
- eccrine sweat glands
- apocrine sweat glands
what are sebaceous glands?
- accompany hair follicles in dermis
- produce sebaceous secretions which lubricate and waterproofs hairs via HOLOCRINE secretion
what are eccrine sweat glands?
- most common sweat glands
- coiled tubes
- in dermis
what are apocrine sweat glands
- specialised sweat glands found in groin, armpits, genitals, anus, external auditory canal (produce ear wax)
describe the shape of the demo-epidermal junction?
- ridged
- has pegs
- these act as anchors
where is the subcutis layer of skin?
beneath the dermis
where is melanin synthesised?
in the melanosomes of melanocyte cells
found in the stratum basale of the epidermis
what are melanocytes derived from.?
melanocytes are derived from tyrosine
