the superficial region
epidermis
the middle region
dermis
the deepest region
hypodermis
there's mostly _______ tissue in the skin
adipose
layer of the epidermis:
stratum ______ (basal layer)
stratum basale
deepest epidermal layer firmly attached to the dermis
single row of stem cells also called stratum
germination: cells undergo rapid division journey from
basal layer to surface takes 25-45 days
stratum basal
layers of the epidermis: stratum _____ (prickly layer)
stratum spinosum
cells contain a weblike system of intermediate prekeratin
filaments attached to desmosomes abundant melanin granules
and dendritic cells
stratum spinosum
layers of the epidermis: stratum ________ (granular layer)
stratum granulosum
thin; 3 to 5 cell layers in which the cells flatten
keratohyaline and lamellated granules accumulate
stratum granulosum
layers of the epidermis: stratum _________ (clear layer)
stratum lucidum
in thick skin thin, transparent band superficial to
the stratum granulosm a few rows of flat, dead
keratinocytes
stratum lucidum
layers of the epidermis: stratum _________ (horny layer)
stratum corneum
20-30 rows of dead, flat, keratinized membranous sacs
3 quarters of the epidermal thickness protects from
abrasion and penetration waterproofs barrier
against biological, chemical, and physical assaults
stratum corneum
strong, flexible, connective tissues cells include
fibroblasts, machrophages, and occasionally mast cells and white
blood cells 2 layers: papillary and reticular
dermis
areolar connective tissue with collagen and elastic fibers and
blood vessels
contains:
capillary loops meissners corpuscles free
nerve ending
dermis: papillary layer
80% thickness of dermis collagen fibers provide
strength and resiliency elastic fibers provide
stretch-recoil properties
dermis: reticular layer
epidermal ridges lie atop deeper dermal papillary ridges to form
friction ridges of _________
fingerprints
_________ fibers arranged in bundles form cleavage (tension) lines
collagen
incisions made ____________ to cleavage lines heal more readily
parallel
____ pigments contribute to skin color
3
yellow to reddish-brown to black, responsible for dark skin
colors produced in melanocytes; migrates to keratinocytes
where it forms pigment shields for nuclei freckles and
pigmented moles
melanin
yellow to orange, most obvious in the palms and soles
carotene
responsible for the pinkish hue of skin
hemoglobin