The resulting pattern of fiber bundles in the skin establishes cleavage lines

The resulting pattern of fiber bundles in the skin

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the skin during normal movement. The resulting pattern of fiber bundles in the skin establishes cleavage lines. Cleavage lines are also called tension linesand Langer lines.Cleavage lines are clinically significant. A cut parallel to a cleavage line will usually remain closed and heal with little scarring. A cut at right angles to a cleavage line will be pulled open as severed elastic fibers recoil, resulting in greater scarring. For these reasons, surgeons choose to make incisions parallel to cleavage lines (Figure 5–9).The Dermal Blood SupplyArteries supplying the skin lie deep within the hypodermis. Branches of these arteries form two networks, or plexuses,in Decubitis Ulcers Problems with dermal circulation affect both the epidermis and the dermis. An ulceris a localized shedding of an epithelium. Decubitis ulcers, or bedsores, affect patients whose circulation is restricted, especially when a splint, a cast, or lying in bed continuously compresses superficial blood vessels. Such sores most commonly affect the skin cover-ing joints or bony prominences, where dermal blood vessels are pressed against deeper structures. The chronic lack of circulation kills epidermal cells, removing a barrier to bacte-rial infection. Eventually, dermal tissues deteriorate as well. (Cell death and tissue destruction, or necrosis, can occur in any tissue deprived of adequate blood flow.) Bedsores can be prevented or treated by frequently changing the posi-tion of the body or by placing patients in specially designed beds containing deflating and inflating air coils. Both ap-proaches vary the pressures applied to local blood vessels.Clinical Notethe dermis. The deeper network lies along the border of the hy-podermis with the reticular layer of the dermis. This network is called the cutaneous plexus(Figure 5–10). Tributaries of these arteries supply both the adipose tissues of the subcutaneous layer and the tissues of the integument. As small arteries travel toward the epidermis, branches supply the hair follicles, sweat glands, and other structures in the dermis.On reaching the papillary layer, the small arteries form an-other branching network, the subpapillary plexus(Figure 5–10). It provides arterial blood to capillary loops that follow the contours of the epidermis–dermis boundary. These capillar-ies empty into small veins of the subpapillary plexus, which drain into veins accompanying the arteries of the cutaneous plexus. This network in turn connects to larger veins in the hypodermis.Trauma to the skin often results in a contusion,or bruise. When dermal blood vessels rupture, blood leaks into the dermis, and the area develops the familiar “black and blue” color.Innervation of the SkinThe integument is filled with sensory receptors. Anything that comes in contact with the skin—from the lightest touch of a POSTERIORANTERIORFigure 5–9 Cleavage Lines of the Skin.Cleavage lines follow the pattern of collagen fiber bundles in the dermis of the skin.
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5162UNIT 2Support and Movement 5-6The hypodermis connects
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