skin Flashcards
what is dermis
tough interwoven matrix of collagen and elastin important in injury. called corneum in hoof and horn
what is stratum corneum
shrunken nuclei + keratin > squames and flakes
what is epidermis
stratified sqamous with following layers of stratum corneum, stratum granulosum - keratinisation, stratum spinosum which is shrunken but retains desmosomes, stratum basale: folded and germinal
what is skin
invaginated epidermal bulb indented by a dermal papilla. squames fuse into a dense solid column of keratin. complex follicles can bear multiple hairs - sometimes seasonal. arrector pilli muscle contract when cold of threatened
functions of the skin
prevent injury, infection and dehydration, protection, thermoregulation, sensation, gland secretion, patterning, movement, economic - leather wool fur ect
how did the skin develop
mesoderm > hypodermis/subcutis, mesoderm > dermatome > trunk/limb dermis. neural crest > melanocytes > facial dermis. ectoderm > epidermis (glands, hair follicles and muscles ect)
what is the hypodermis
loose connective tissue and fat which allows considerable mobility. site of emphysema, oedema and subcutanous injections. excess skin may form DEWLAPS
what are adipocytes
cells most able to change shape, large lipid droplet vacuole surrounded by a thin rind of metabolically active cytoplasm. symp innervation.
white fat is for….
storage
brown fat is for…..
thermogenesis
variations in epidermis?
thickness, no vessels only tips of nerves, surface markings such as nasal planum, pad conical papillae and pad ridges). pigmentation from melanocytes, papillae/ridges increase grip on ground
features of hair
specialised form of epidermal keratinisation. insulation role, sensory fibres growing from scale hinges suggests evol from scales/feathers?
hair growth phases 3
anagen (growth) > catagen (follicle atrophy) > telogen (old hair displaced by new)
what are the different hair types
1 guard/cover/topcoat hairs - promoting water run off. 2 lanugo/undercoat - wool. 3 vibrissae/whiskers - follicle embedded deep in a densely innervated venous plexus
what are simple sebaceous glands
secrete sebum (lanolin in sheep), they form when cells rupture = ‘holocrine’ cells. discharged into hair follicles or directly to surface.
what do simple sebaceous glands secrete
triglycerides, unique wax, squalene, mainly lipid based on glycerol. antimicrobial lipids, immunoglobulins, vitamin E and antioxidants to keep skin pliable and water proof
what are specialised glands
ceruminous > earwax, tarsal (eyelids)> superficial layer of tear film
what is another form of gland
scent
what are anal glands
found in par anal sac OF ANAL CANAL, 4&8oclock with single duct opening at anocutaneous junction (duct opens at gut to epidermis).
what emptied anal glands
external striated anal sphincter
what is the circumanal
hepatoid glands, external peri-anal surface in the furthest bit of skin around the anus
what are apocrine glands
secrete sweat into hair follicles > albcentinous
what controls apocrine glands
hormonal - adrenaline in horses/humans
how do apocrine glands secrete sweat
secrete in membrane bound vesicles into the lumen - apocrine.
what do apocrines specifically excrete
proteinacious stuff to form a foam
what are ecrine glands
sweat glands that secrete directly onto the surface of the skin not via a hair follicle.
outline the process of eccrine gland secretion
surface pores>watery sweat of pads and nose
what type of innvervation is on eccrine glands
adrenergic (animals) sympathetic innervation
how do eccrine glands secretion (mechanism)
by exocytosis: merocrine
what are eccrine glands in the male platypuses?
venomous
are eccrine glands heavily relied on
no
