Surface of epidermis hair follicle surface of

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Human Physiology: From Cells to Systems
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Chapter 12 / Exercise 07
Human Physiology: From Cells to Systems
Sherwood
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Surface of epidermisHair follicleSurface of external auditory canal or into ducts of sebaceous glandsSecretionSebum (mixture of triglycerides, cholesterol, proteins), and inorganic salts Less viscous; consists of water, ions (Na+, Cl), urea, uric acid, ammonia, amino acids, glucose, and lactic acid More viscous; consists of the same components as eccrine sweat glands plus lipids and proteins Cerumen, a waxy materialFunctionsPrevent hairs from drying out, prevent water loss from skin, keep skin soft, and inhibit growth of some bacteria Regulation of body temperature, waste removal, and stimulation during emotional stress Stimulation during emotional stress and sexual excitement Impede entrance of foreign bodies and insects into external ear canal, waterproofs canal, and prevent microbes from entering cellsOnset of functionRelatively inactive during childhood; activated during puberty Soon after birthPubertySoon after birthFigure 5.7Nails. Shown is a fingernail.Nail cells arise by transformation of superficial cells of the nail matrix.Free edgeextends pastthe finger or toeFree edgeNail body(plate)LunulaEponychium(cuticle)Nail rootDermisPhalanx(finger bone)Nail rootis the portionthat is notvisibleEponychium(cuticle) is the stratum corneum of the epidermisLunula is the thick,white partof the nailNail matrixis the epithelium proximal to the nail root. It contains dividing cells, which produce new nail cells(b) Sagittal section showing internal detail(a) Dorsal viewNail bodyis the visibleportion ofthe nailNail bedis the skinbelow thenail plateSagittal planeEpidermisHyponychiumsecures nail tothe fingertipFIGURE5.7 CONTINUES
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Human Physiology: From Cells to Systems
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Chapter 12 / Exercise 07
Human Physiology: From Cells to Systems
Sherwood
Expert Verified
134CHAPTER 5THE INTEGUMENTARY SYSTEMTABLE 5.4Comparison of Thin and Thick SkinFEATURETHIN SKINTHICK SKINDistributionAll parts of the body except areas such as palms and palmar surface of digits, and solesAreas such as the palms, palmar surface of digits, and solesEpidermal thickness0.10–0.15 mm (0.004–0.006 in.)0.6–4.5 mm (0.024–0.18 in.), due mostly to a thicker stratum corneumEpidermal strataStratum lucidum essentially lacking; thinner strata spinosum and corneum Strata lucidum present; thicker stratumspinosum and corneumEpidermal ridgesLacking due to poorly developed and fewer and less-well-organized dermal papillae Present due to well-developed and more numerous dermal papillae organized in parallel rowsHair follicles and arrector pili musclesPresentAbsentSebaceous glandsPresentAbsentSudoriferous glandsFewerMore numerousSensory receptors SparserDenserFIGURE5.7 CONTINUEDPhalanx(finger bone)Nail rootSudoriferous(sweat)glandsDermisEpidermisEponychium(cuticle)Nail bodyHyponychiumNail bedDermalpapillae5x

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