Are also composed of dead epidermal cells that are

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are also composed of dead epidermal cells that are converted to keratin. Newcells are converted at the nail root and are pushed towards the external surface in the direction ofthe nail body. Thenail bodyis the visible portion of a nail, covering the epidermis in that region,called a nail bed. Thenail rootis not visible. The stratum corneum of the epidermis extends fromthe nail root covering the visible portion of the nail, called thecuticle. Thelunulais the visibleportion of the nail bed near the nail root, which is typically crescent shaped (and most visible on thethumbs).
Figure 7.9 Cross section of a nail root and nail body.Physiology of the Integumentary System: RepairThe smallest unit of life is a cell. Cells come together to form tissues.Tissuesare comprised of cellswhich are similar in structure and function. Tissues are comprised of cells andmatrix. Matrix is alsocalledextracellular material, made up of ground substance (extracellular fluid), protein and collagenfibers. When the skin is damaged, both tissue and matrix need to be repaired.Tissue repairIn the case of tissue damage, the body needs to respond quickly prevent blood loss in andmicroorganisms from entering the bloodstream. Tissues, such as the skin, can be repaired by thebody through a multi-step process(Figure 7.10). Bloodplatelets(Figure 7.11)from the brokenblood vessel start to accumulate in the area where the tissue was damaged, forming aclot,secreting a mesh-like substance around it to prevent blood loss(Figure 7.11).
Figure 7.10 Tissue damage: skin is cut by a foreign object.
Figure 7.11 Tissue repair:Platelets gather in the broken blood vessel and form a clot.Mast cellsreleasehistamine, a chemical which helps to dilate blood vessels to bring increasedblood and nutrients to the injured area. Histamines help to initiate a localinflammatory response,which signals other cells in the area to help remove foreign pathogens.Macrophages(a type ofwhite blood cell) work to engulf and destroy disease-causing pathogens. Once the dead and foreigncells are removed, the body can begin to replace the damaged cells.Fibroblasts(Figure 7.12)helpto secrete new collagen in the shape of the old tissue. This collagen framework supports the tissuematrix in the shape of the old cells until new cells are fully developed(Figure 7.13).
Figure 7.12 Tissue repair: Fibroblasts secrete a collagen matrix in the shape of the original tissue.Figure 7.13 Tissue repair:collagen network fills in the damaged area as the cells divide andmature.
Remodelingis the final phase of wound healing where the tissue matures, and the cells begin totake on their original functions(Figure 7.14). If the wound is too deep in the tissue a scar forms andsome of the original function of the tissue is lost. Ascaris an overgrowth of the fibrous connectivetissue which cannot be fully replaced by the original tissue.Figure 7.14 Tissue remodeling:Cells divide, mature, and fully replace the damaged tissue.BurnsOne of the ways that the skin can be injured is through aburn. Burns are classified through theseverity of the burn.First degree burns

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Term
Spring
Professor
N/A
Tags
Human Anatomy, cells, Stratum Corneum

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