chapter 6 Flashcards
epidermis
derived from ectoderm, embryo layers
basement membrane
between epidermis and dermis
first cell layer (stratum basale)
deepest cell layer where active mitosis produces new cells for the epidermis
second layer (periderm)
one cell layer thick in embryo, but become multiple layers in adult
dermis
derived from dermatome
-one of three cell populations in the somite of the embryo
underlying connective tissues (hypodermis, superficial fascia)
below the dermis and holds the integument down the superficial muscle
-may be a lot of adipose tissue here too
during growth, invasion of dermis occurs
neural crest cells produce chromatophores (pigment cells)
-blood vessels and nerves
epidermis keratinized
this is done for protection
keratinocytes
cells accumulating keratin
-keratin is second most important adaptation allowing amniotes to become fully terrestrial
stratum basale
mitosis
stratum corneum
outer layer of dead keratinocytes
callus
skin with thick stratum corneum
hair
keratin structures projecting from follicles in dermis
-cells lining dermal papillae secrete keratin that produces the hair (matrix cells)
matrix cells
within hair papillae produce keratin
-continually produce keratinocytes
arrector pili
muscles that erect hair in response to cold or fear
vibrissae
whiskers, used for nocturnal motion detection
quills
thickened hairs for defense
sebaceous glands
produce oily secretion (sebum) to protect hair
sebum
oily secretion used to protect hair
sweat glands
produce watery secretion (sweat) to cool body
sweat
watery secretion to cool body
scent glands
modified sweat and function as social communication… mark territory, identify individuals or for courtship
mammary glands
modified sebaceous glands, functional only in females, produce milk for young
keratin specializations
nail, claw, hooves
horns
bony projection from skull plus overlying integument-derived keratin sheath
-what you see is keratin, not bone
-horns in both males and females but larger in males
-usually unbranched and grow throughout the life of the individual
keratin sheath
keratin outer layer
antlers
bone covered by skin when growing
-what you see is just bone
-branched
-only males have them
antlers fall off each year and have to be regrown
velvet
covers antlers and falls off when antler is fully developed
baleen
whales don’t have teeth but have hairlike structures made of keratin that are used for filtering out small crustaceans from the water
giraffe
horns are stunted antlers in velvet throughout life
-both males and females have them
rhinoceroses
hair horns
-made of keratinized epidermal fibers
-no bony core
caribou
antlers in both sexes
-antlers shed annually
pronghorn antelope
branched horns
-outer keratinized sheath is branched but not the inner bony core
-both sexes have them
-outer keratinized sheath is shed annually, but not the inner bony core
placoid scales
Chondrichthyes
-enamel exterior and dentin interior
-internal pulp cavity
-forerunner of the tooth
collagen plies
dermal collagen forms distinct layers that permit flexure without wrinkles
-45 degree angles
Osteichthyes mucus
unicellular glands in epidermis produces this
plates (scales)
dermis produces this
cosmoid scales
bone + dentin + enamel
ganoid scales
bone + enamel
teleost scales
only bone
thin epidermis (thin stratum corneum)
permits cutaneous respiration
-oxygen to diffuse through water, through skin into capillaries below skin
-important respiratory organ
mucus (and poison) glands
present in amphibians
reptile scutes
boneless epidermal scales are thick patches of keratin
molt
entire epidermis may be lost during this
