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 ( mm) 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 binds epidermis to underlying tissues irregular dense connective tissue on average mm thick 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 varying amounts of melanin varying size of melanin granules (darker skin, larger granules) albinos lack melanin Environmental Factors sunlight UV light from sunlamps X rays Physiological Factors dilation of dermal blood vessels constriction of dermal blood vessels carotene (yellow pigment in yellow vegetables) jaundice (liver malfunction)

Healing of Burns First degree burn – superficial partial- thickness (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.

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. Healing of Burns (cont.)

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

2 ND DEGREE BURN (SUPERFICIAL PARTIAL TICKNESS)

2 ND DEGREE BURN (DEEP PARTIAL TICKNESS)

3 RD DEGREE BURN (FULL THICKNESS)

4 TH 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