Chapter 6 THE INTEGUMENTARY SYSTEM•Skin –Cutaneous membrane covering the entire body–Largest organ (22 square feet; 1 – 2 mm thick; 10 lbs)•Skin derivatives–Sweat glands–Oil glands–Hairs–Nails
2SKIN FUNCTIONSProtects deeper tissues from:•Mechanical damage•Chemical damage•Bacterial damage•Thermal damage•Ultraviolet radiation•Desiccation – drying out•Aids in heat regulation•Aids in excretion – 400mL water, salt, urea, carbon dioxide•Synthesizes vitamin D – activated by UV light
3FUNCTIONS OF SKIN -- THERMOREGULATION•Perspiration & its evaporation –lowers body temperature–flow of blood in the dermis is adjusted•Exercise–in moderate exercise, more blood brought to surface helps lower temperature–with extreme exercise, blood is shunted to muscles and body temperature rises•Shivering and constriction of surface vessels–raise internal body temperature as needed
4LAYERS OF THE SKIN•The superficial portion of the skin is the epidermis–It is composed of epithelial tissue.•The deeper layer of the skin is the dermis –It is primarily composed of connective tissue.•Deep to the dermis is the subcutaneous layeror hypodermis. (nota part of the skin)–It consistsof connective and adipose tissue.
5LAYERS OF SKIN: EPIDERMIS•Stratified squamous epithelium–avascular (contains no blood vessels)–4 types of cells–5 distinct strata (layers) of cells
6FOUR PRINCIPLE CELLS OF THE EPIDERMIS•keratinocytes - produce the protein keratin, which helps protect the skin and underlying tissue from heat, microbes, and chemicals, and lamellar granules, which release a waterproof sealant •Melanocytes - produce the pigment melanin which contributes to skin color and absorbs damaging ultraviolet (UV) light•Langerhans cells - participate in immune response•Merkel cells- contact a sensory structure called a tactile (Merkel) disc and function in the sensation of touch
7LAYERS (STRATA) OF THE EPIDERMISStratum corneum - Constant exposure to friction will cause this layer to increase in depth with the formation of a callus, an abnormal thickening of the epidermis.Stratum lucidum(clear layer)—cells filled with keratin precursor; found in thick skin
8LAYERS (STRATA) OF THE EPIDERMISWhen the basal layer of the epidermis is destroyed, new skin cannot regenerate with a skin graf.Stratum basale(base layer)—single layer of columnar cells; only these cells undergo mitosis, then migrate through the other layers until they are shedStratum spinosum(spiny layer)—cells arranged in 8 to 10 layersStratum granulosum(granular layer)—cells arranged in two to four layers and filled with granules that contain high levels of lysosomal enzymes
9LAYERS OF THE SKIN: DERMIS•Connective tissue layer deep to the epidermis•Much thicker than the epidermis•Contains hair follicles, glands, nerves & blood vessels
LAYERS OF THE DERMIS•Papillary layer–Dermal papillae extending into the epidermis–Loose Areolar Connective tissue•Reticular layer–Dense collagen and elastin fiber
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Term
Fall
Professor
TBD
Tags
Skin Cancer Foundation, Stratum lucidum, Stratum Corneum
