Integument and Barriers to Infection Flashcards
dermal-epidermal junction
surface of palms/soles has epidermal ridges with intervening furrows
each ridge follows the outline of an underlying dermal ridge/papilla – hemidesmosomes create tight junction
Layers of Epidermis
Stratum: Corneum lucidum (not in thin skin) granulosum spinosum basale
stratum basale
mitotically active layer
replaces skin every 15-30 days
single layer of cuboidal, low columnar cells bound to keratinocytes apically
stratum spinosum
polyhedral keratinocytes
produces cytokeratin which aggregates to tonofilaments
malpghian layer
consists of the stratum basale and the stratum spinosum
stratum granulosum
contain granules
1) keratohyalin granules: basophilic, non-membrane bound granules (cystine and histadine rich protein, assembles keratin into bundles)
2) lamellar granules: lipid rich, barrier to foreign material and water loss
stratum lucidum
translucent band of cells with no organelles or nuclei
densely packed keratin filaments
stratum corneum
multiple layers of cells with mature keratin (Squames == fully keratinized)
continuously shed
thick skin: 15-40 layers
thin skin: 10-20 layers
melanocytes
originate from neural crest - first cells to arrive in epidermis
located in stratum basale - contacts about 36 keratinocytes, imparting melanin to the differentiating cells in granules
langerhans cells
originate from bone marrow - found in stratum of malpighi (mostly the stratum spinosum) - peripheral dendritic cells == APCs
Merkel cells
derived from neural crest - nonencapsulated tactile mechanoreceptors - associated with basal lamina (stratum basale), cytoplasm contains granules, small nerve plate is connected to myelinated axon
light touch, more numerous in thick skin
keratinocytes
makes keratin and lamellar granules
form squames in stratum corneum
houses melanin, pigment protein
melanin
pigment protein that protects nuclei from UV radiation
melanin production
tyrosinase converts tyrosine into DOPA in the presence of UV light
DOPA is polymerized to melanin
dermal layers
papillary layer: superficial, loose (areolar) CT - meissner corpuscles and dermal papilla
sub-papillary plexus, capillary branches provide nutrient source
reticular layer: deep, dense irregular CT (type I collagen) - with elastic fibers, more fibers and fewer cells
hypodermis
subq tissue
vascular, fat resides here
free nerve endings
simple, numerous afferent fibers
dermal-epidermal junction
temperature, touch, itch, pain
Meissner Corpuscle
encapsulated
dermal papillae of fingertips, palms, soles
light touch, low frequency
Pacinian Corpuscle
CT capsule surrounds 15-50 think, concentric layers
reticular dermis or hypodermis
coarse touch, vibration, pressure
merocrine/eccrine gland
exocytosis of apical end cells
holocrine glands
disinigration of cell with contents becoming secretion
cell secretes its w[hol]e body
apocrine gland
membrane enclosed vesicles
suderiferous glands
eccrine (merocrine)
acinus- simple cuboidal surrounded by myoepithelial cells
duct - stratified cuboidal epithelium
myoepithelial cells
surround an acinus and express its content by squeezing it
eccrine sweat glands
found extensively throughout skin
produce sweat used for thermoregulation
components: water, salt, ammonia, uric acid and mucinogen granules
apocrine glands
restricted to axilla, circumanal region, areolar
merocrine secretion - milky sweat secretion
responds to hormones and adrenergic (fight of flight) signals
sebaceous glands
face, scalp, fair follicles
produce lipid mixture, sebum via holocrine secretion
simple branched acinar
single duct
waxy mix of TAGs and cholesterol - lubricates and waterproofs skin
hair shaft
medulla - core
cortex - middle layer
cuticle - outer layer
vellus vs terminal hair
vellus = baby hair terminal = AK chest carpet
nails
highly keratinized cells on bed of epidermis
nail root - primal region of plate
nail plate remains attached to nail bed and pushed forward by continous growth
lanula: crescent shaped white area near nail matrix
