Integumentary System- (Chapter 5) Integument = “covering” ~16% of body mass: ~2 meter2. Composed of: 1. Cutaneous membrane: A. Epidermis - superficial epithelium B. Dermis - underlying CT w/ blood supply 2. Accessory structures A. Hair B. Nails C. Exocrine glands Functions: 1. Protect underlying tissues from infection, exposure and dehydration. 2. Excrete salts, water, and organic waste. 3. Maintain normal body temp (conserve and radiate heat). 4. Synthesize Vitamin D3 for calcium metabolism. 5. Store nutrients (fat). 6. Sensory detection: touch, pressure, pain, and temp. Epidermis (on handout). The corrugated border between dermis and epidermis helps bond epidermis to dermis (increased surface area for attachment). In thick skin epidermal ridges show on the surface as fingerprints: function to enhance gripping. Epidermis water resistant but not water proof: Insensible perspiration = water loss through. epidermis: ~500ml (1 pint) / day (more if damaged, e.g. burn). Callus = thickening of epidermis, due to repeat friction. Blister = separation of epidermal layers or epidermis from dermis, space fills with interstitial fluid.. Skin Color Pigment based: epidermal pigments and blood pigments contribute to the color. 1. Epidermal Pigmentation: A. Carotene: yellow-orange, from diet -converted into Vitamin A, -localized to epithelium, -functions in normal maintenance of epithelia and photoreceptors, -excess accumulates in stratum corneum. B. Melanin: brown, from melanocytes: -for UV protection. Melanocytes: in stratum basale: -synthesize melanin from tyrosine (amino acid), -packaged in melanosomes, -transferred to cytoplasm of keratinocytes ,-cluster around top side of nucleus, -eventually digested by lysosomes. Everyone has ~1000 melanocytes /mm2: -pale people: small melanosomes, present only in stratum basale and spinosum, -dark people: larger, greater number of melanosomes, retained up through stratum granulosum. Freckle = overproduction of melanin from single melanocyte UV exposure:-some needed for Vitamin D3 production, -excess = damage (DNA mutation), -fibroblasts ! altered CT structure, wrinkles, -epidermal cells, melanocytes ! cancers: squamous cell carcinoma melanoma 2. Dermal Circulation: hemoglobin pigment -oxygenated blood = red color, hemoglobin in RBCs, through skin looks pink *vasodilation ! skin looks more red *vasoconstriction ! skin looks more pale, -Cyanosis = low oxygen, blood deep purple, skin appears blue/purple results from low temp, heart failure, asthma. Abnormal skin color: -Jaundice: liver fails to excrete bile, accumulates in skin, yellow. -Addison’s Disease: pituitary secretes excess adrenocorticotropic hormone, stimulates melanocytes, excess melanin, bronzing. -Albinism: genetic mutation in melanin biosynthesis pathway, lack pigmentation in skin, hair and eyes. -Vitiligo: autoimmune disease ! destruction of melanocytes. Vitamin D3 Production:Cells of stratum spinosum and basale. UV energy + cholesterol = Vitamin D3. Vitamin D3 used by kidney to synthesize the hormone calcitriol. Calcitriol necessary to signal small intestine to absorb calcium. No VitD ! no calcitriol ! no calcium absorption ! weak bones. Dermis (on handout) Collagen fibers from reticular layer blend into papillary and subcutaneous layers to attach integument to body: -wrinkles = dermis stretched beyond its elastic capacity, collagen fibers damaged. -stretch marks = collagen & elastic fibers torn. -collagen & elastin fibers arranged in parallel bundles aligned to resist the expected direction of force = lines of cleavage. -cuts parallel to lines of cleavage will heal faster and with less scar than those perpendicular. Dermis highly vascularized: must “feed” itself and epidermis above. Contusion = bruise, trauma that ruptures blood vessels but does not break skin, blood pools in dermis and must be removed by phagocytes (slow process). Sensory perception in integument: Skin highly innervated for sensory perception, mostly in dermis: 1.