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Derivitives of skin

Derivitives of skin - 6 eg wavy hair is oval eg tightly...

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“Derivitives of skin” during embryonic development 1000’s of small groups of epidermal cells from stratum basale push down into dermis to form hair follicles and glands 1. Hair covers entire body except palms, soles, lips, nipples, parts of external genitals hormones account for the development of “hairy” regions: eg. head, axillary and pubic areas humans are born with as many follicles as they will ever have hairs are among the fastest growing tissues in the body formation similar to epidermis heavily keratinized consists of: shaft : visible part root: follicle : sheath surrounding root papillae : vascularized, growing part of hair Arrector Pili muscles attached to follicle causes hair to stand on end (cold, fright) oil glands : 2/follicle hair receptor: entwines each follicle, responds to hair movements hair color depends on kinds (yellow, rust, brown, and black) and the amount of melanin cortex of shaft contains hair texture related to differences in cross-sectional shape eg. straight hair is round Human Anatomy & Physiology: Integumentary System, Lecture Notes, Ziser, 2005
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Unformatted text preview: 6 eg. wavy hair is oval eg. tightly curly hair is relatively flat 2. Nails scale-like modification of the epidermis fingernails and toenails are clear,hard derivatives of stratum corneum very thin, dead, scaly cells, densely packed together corresponds to hoof or claw of animals most mammals have claws, flat nails are a primate characteristic ‡ more fleshy and sensitive fingertips ‡ still can be used for digging and picking apart food, etc features: nail matrix: growth zone beneath proximal skin nail bed composed of stratum basale nail plate: visible portion of nail fingernails grow ~1 mm/wk; toenails more slowly [adding gelatin to diet has no effect on growth or hardness of nails] appearance of nails has diagnostic value: eg. spoonlike, flat, concave ‡ may indicate iron deficiency eg. clubbed or swollen fingertips ‡ long term hypoxemia from eg congenital heart defects and emphysema...
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