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Skin and the Integumentary System Skin and the Integumentary System • Composed of several tissues • Maintains homeostasis • Protective covering • Retards water loss • Regulates body temperature • Houses sensory receptors • Contains immune system cells • Synthesizes chemicals • Excretes small amounts of waste Layers of Skin 1. Epidermis 2. Dermis 3. Subcutaneous layer Epidermis • lacks blood vessels • keratinized • thickest on palms and soles (0.8-1.4mm) • melanocytes provide melanin • rests on basement membrane • stratified squamous Epidermis (cont.) Layers of Epidermis • stratum corneum • stratum lucidum • stratum granulosum • stratum spinosum • stratum basale Dermis • on average 1.0-2.0mm thick • binds epidermis to underlying tissues • irregular dense connective tissue • muscle cells • nerve cell processes • blood vessels • hair follicles • glands Subcutaneous Layer • hypodermis • loose connective tissue • adipose tissue • insulates • major blood vessels Hair Follicles • epidermal cells • tube-like depression • extends into dermis • hair shaft • hair root • hair papilla • dead epidermal cells • melanin • arrector pili muscle Nails • protective coverings • composed of: nail plate, nail bed and lunula Sebaceous Glands • usually associated with hair follicles • holocrine glands (secrete entire cell) • secrete sebum (fatty material + cellular debris) • absent on palms and soles Sweat Glands • or sudoriferous glands • widespread in skin • deeper dermis or hypodermis • eccrine glands (or merocrine, forehead, neck and back) • apocrine glands (axillary region, groin, around nipples) • OTHER GLANDS: ceruminous glands (external ear canal) AND mammary glands (milk) Problems in Temperature Regulation Hyperthermia – abnormally high body temperature Hypothermia – abnormally low body temperature Skin Color Genetic Factors Physiological Factors • varying amounts of • dilation of dermal blood melanin vessels • varying size of melanin • constriction of dermal blood granules (darker vessels skin, larger granules) • carotene (yellow pigment in • albinos lack melanin yellow vegetables) • jaundice (liver malfunction) Environmental Factors • sunlight • UV light from sunlamps • X rays Healing of Burns • First degree burn – superficial partialthickness (injures only epidermis). Skin will be red, swollen, painful and sensitive to touch. Usually heals in 1-2 days. Mild sunburn is a common 1st degree burn. • Second degree burn – deep partial-thickness (some epidermis and some dermis). Skin will be painful, swollen, red, and blistered or oozing fluid. Healing of Burns (cont.) • Third degree burn – full-thickness (destroys epidermis, dermis and accessory organs of skin) • autograft (from own body) • homograft (from cadaver) • various skin substitutes (amniotic tissue, lab skin) • extensive scars • The skin will be black, white, and charred. • There is less pain because the nerves have been destroyed. • Fourth Degree Burn: extends through entire skin, and into underlying fat, muscle and bone. • requires excision (amputation, significant functional impairment and, in some cases, death) • painless (nerves have been destroyed) FIRST DEGREE BURN 2ND DEGREE BURN (SUPERFICIAL PARTIAL TICKNESS) 2ND DEGREE BURN (DEEP PARTIAL TICKNESS) 3RD DEGREE BURN (FULL THICKNESS) 4TH DEGREE BURN Rule of Nines Life Span Changes • Scaly skin • Age spots • Dermis becomes reduced • Loss of fat • Wrinkles • Sagging • Sebaceous glands secrete less oil • Melanin production slows • Hair thins • Number of hair follicles decrease • Impaired nail growth • Sensory receptors decline • Inability to control body temperature • Less vitamin D production Clinical Application Acne Vulgaris • most common skin disorder • sebum and epithelial cells clog glands • produces whiteheads and blackheads • anaerobic bacteria trigger inflammation (pimple) • largely hormonally induced • androgens stimulate sebum production • treatments include antibiotics and topical creams