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A&P 1 _ 7th mod.docx - Introduction to the Integumentary...

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Introduction to the Integumentary SystemThe integumentary systemis comprised of theskin, hair, and nails.Skinis the largestorgan of the body. It is made up of theepidermis(outer layer),dermis(middle layer),and thehypodermis(inner, also calledsubcutaneoustissue layer). SeeFigure7.1below to see the three layers of the skin. Skin cells absorb ultraviolet radiation toproduce vitamin D, which is used to promote bone development. The integumentarysystem contains the sensory receptors and glands used for protection of the skin andunderlying tissues. The integumentary system plays an important role in protectinginternal organs from extreme temperature changes as well as pathogenic (disease-causing) microorganisms. If the integumentary system is damaged and microbes orforeign objects make their way into the body, it is thelymphatic systemthat isresponsible for mounting the attack to defend the body’s internal environment.
GlandsRecallendocrine glandssecretehormones,which are secreted in the bloodstream forbody-wide distribution.Exocrine glandscontain secretions released throughaduct(opening) into an epithelial surface or lining. Exocrine gland secretions can alsorelease their contents onto the surface of the skin. Other types of exocrine glandsrelease their contents into an epithelial surface. (Recall, for example, that salivaryamylase is released into the mouth.)Exocrine glands can be categorized by their shape and structure. Most glands in thebody aremulticellular glands, which are set within epithelial tissue and release theircontents through a duct to the surface.Sebaceous glands(oil glands)producesebum(Figure 7.3). Sebum helps to keep the skin and hair from drying outand inhibits the growth of harmful microorganisms.Sweat glands(sudoriferous glands)produce sweat in almost every part of the skin. Notice (seeFigure 7.3) that thesecretory portion is deep within the dermis layer of the skin. The duct extends all theway through the dermis, through the epidermis to release its contents on the externalsurface. The release of sweat is calledperspiration. Perspiration helps the body toregulate its temperature through a process calledthermoregulationby releasing heatfrom the body.
The EpidermisTheepidermis(outermost layer of skin) is made up ofstratified squamousepithelium.(Stratifiedmeans layered, andsquamousmeans flat). The epidermis isavascular,meaning it does not have a direct blood supply. The epidermis receives its nutrientsfrom the basement membrane (basal lamina).The epidermis is comprised of four distinct layers (listed from superficial to deep): thestratum corneum, stratum granulosum, stratum spinosum, and stratum basale(Figure7.4). The stratum basale is firmly adhered to thebasement membrane, which containsthe blood supply for the epidermis.

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Term
Fall
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Stratum Corneum

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