Burns Thermal injury or lesion Estimating surface area Contact with hot object Contact with fire Ultraviolet light Electric current Corrosive chemical Estimating surface area Rule of Palms Rule of Nines

Burns First-degree burn Minor discomfort Reddening of skin No blistering Tissue destruction is minimal

First Degree Burn

Burns Second-degree burn Injury to the upper layers of the dermis Damage to sweat glands, hair follicles, and sebaceous glands Tissue death is not complete Blistering Severe pain Generalized swelling Edema Scarring is common

Second Degree Burn

Burns Third-degree burn Destruction of both epidermis and dermis Tissue death below follicles and glands May involve muscles, fasciae, or bone Insensitive to pain immediately after injury Destruction of nerve endings Scarring is a serious problem

Third Degree Burn

Appendages of the Skin Hair Distribution Types Over entire body except palms of hands and soles of feet and a few other small areas Types Lanugo Fine and soft hair covering the fetus by the 6th month of pregnancy Usually lost by birth Vellus Stronger, finer, less pigmented hairs Terminal Replaces 80-90% of the vellus hair on the chest and extremities in males Females have less vellus hair replaced than males

Appendages of the Skin Hair (cont.) Development of hair Growth begins when cells of the epidermis spread down into the dermis, forming a small tube, the follicle Follicles consist of two primary layers Outer dermal root sheath Epithelial root sheath Internal layer External layer Stratum germinativum forms innermost layer of follicle and germinal matrix Mitosis of cells of germinal matrix forms hairs

Appendages of the Skin Hair (cont.) Papilla Root Shaft Medulla Cortex Small mound of the dermis protruding into germinal matrix Contains a cluster of capillaries under germinal matrix Root Part of hair embedded in follicle in dermis Shaft Visible part of hair Medulla Inner core of hair Cortex Outer portion of hair Cuticle Covering layer

Appendages of the Skin Hair (cont.) Appearance of hair Color Growth Result of different amounts, distribution, types of melanin in cortex of hair Growth Hair growth and rest periods alternate Hair on head averages 5 inches of growth per year Sebaceous glands Attach to and secrete sebum (skin oil) into follicle Male pattern baldness results from combination of genetic tendency and male sex hormones

Appendages of the Skin Nails Consist of epidermal cells converted to hard keratin Nail body Visible part of each nail Root Part of nail in groove hidden by fold of skin, the cuticle Lunula Moon-shaped white area nearest root

Appendages of the Skin Nails (cont.) Nail bed Growth Layer of epithelium under nail body Contains abundant blood vessels and appears pink under translucent nails Nails may have pigmented streaks Separation of nail from nail bed is called onycholysis Growth Nails grow by mitosis of cells in stratum germinativum beneath the lunula Average growth about 0.5 mm per week, or slightly over 1 inch per year

Appendages of the Skin Skin glands Two types of sweat glands Eccrine glands Most numerous sweat glands; quite small Distributed over total body surface with exception of a few small areas Simple, coiled, tubular glands Function throughout life Secrete perspiration or sweat; eliminate wastes; and help maintain a constant core temperature 3,000 per in2 on the palms of the hands

Appendages of the Skin Two types of sweat glands (cont.): Apocrine glands Located deep in subcutaneous layer Limited distribution—axilla, areola of breast, and around anus Large (often more than 5 mm in diameter) Simple, branched, tubular glands Begin to function at puberty Secretion shows cyclic changes in female with menstrual cycle

Appendages of the Skin Skin glands (cont.) Sebaceous glands Secrete sebum Oily substance that keeps hair and skin soft and pliant Prevents excessive water loss from the skin Lipid components have antifungal activity Simple, branched glands Found in dermis except in palms and soles Secretion increases in adolescence May lead to formation of pimples and blackheads

Appendages of the Skin Skin glands (cont.) Ceruminous glands Modified apocrine sweat glands Simple, coiled, tubular glands Empty contents into external ear canal alone or with sebaceous glands Mixed secretions of sebaceous and ceruminous glands called cerumen (wax) Function of cerumen to protect area from dehydration Excess secretion can cause blockage of ear canal and loss of hearing

Cycle of Life: Skin Children Skin is smooth, unwrinkled, and characterized by elasticity and flexibility Few sweat glands Rapid healing

Cycle of Life: Skin Adults Development and activation of sebaceous and sweat glands Increased sweat production Body odor Increased sebum production Acne

Cycle of Life: Skin Old age Decreased sebaceous and sweat gland activity Wrinkling (Figure 6-21) Decrease of body’s ability to cool itself

The Big Picture: Skin and the Whole Body Skin is a major component of the body’s structural framework Skin defines the internal environment of the body Primary functions are support and protection