The integumentary system includes the skin, hair, and nails. The skin plays a major role in the concept of body protection. As shown in Fig. 26-1, the skin protects against foreign invasion by providing a first line of defense (the moat), a second line of defense (the castle wall), and even a third line of defense (the knights and soldiers). The normal flora on the surfaces of skin and mucous membranes repels some of the more harmful microorganisms. Intact skin has barrier functions, alarm functions, and even combat functions. Specialized cells called Langerhans’ cells, present in the skin, engulf foreign substances (antigens) that invade the body when the skin is injured. These cells then alert the immune system to the presence of the invader.

FIG. 26-1 Role of the skin in the concept of body protection.

The skin is the largest organ of the body and plays a major role in homeostasis. When intact, it helps regulate body temperature and maintains fluid and electrolyte balance. Changes in the skin can communicate information about a person’s health and well-being (Anderson et al., 2007).

Emotional stress, systemic disease, and skin injury or disease can alter the function, appearance, and texture of the skin. Therefore examine the skin for important clues about the patient’s health.

The sensory function of the skin allows the use of touch as a therapeutic intervention to provide comfort, relieve pain, and communicate caring. Because the skin has many sensory receptors, the patient can report subjective skin sensations that might indicate specific health problems.

Anatomy and Physiology Review

Structure of the Skin

As shown in Fig. 26-2, the skin has three layers: subcutaneous tissue (fat), dermis, and epidermis. Each layer has unique properties that contribute to the skin’s ability to maintain its complex functions.

FIG. 26-2 Anatomy of the skin.

Subcutaneous fat (adipose tissue [fat]) is the innermost layer of the skin, lying over muscle and bone. Fat cells serve as an energy reserve in the event extra calories are needed to power the body. These cells also act as heat insulators for the body. They absorb shock and protect against injury by padding internal structures. Fat distribution varies with body area, age, and gender. Many blood vessels go through the fatty layer and extend into the dermal layer, forming capillary networks that supply nutrients and remove wastes.

The dermis (corium) is the layer above the fat layer. It is composed of connective tissue that contains no cells. The dermis is composed of collagen and elastic fibers that are interwoven to give the skin both flexibility and strength.

Collagen, the main component of dermal tissue, is a protein formed by dermal cells called fibroblasts. Collagen production increases in areas of tissue injury and helps form scar tissue. Fibroblasts also produce ground substance, a protein lubricant that surrounds the dermal cells and fibers and contributes to the skin’s normal suppleness and turgor.

The elasticity of the skin depends on both the amount and quality of the elastic fibers, which are scattered among the collagen fibers. The major component of the elastic fiber is elastin.

The dermis has capillaries and lymph vessels for the exchange of oxygen and heat. The dermis is also rich in sensory nerves that transmit the sensations of touch, pressure, temperature, pain, and itch.

The epidermis is the outermost skin layer. It is anchored to the dermis by finger-like projections of dermal tissue (dermal papillae). The fingers of epidermal tissue that project into the dermis are called rete pegs. The epidermis is less than 1 mm thick, but it is the protective barrier between the body and the environment.

The epidermis does not have its own blood supply and receives its nutrients by diffusion from the blood vessels in the dermal layer through the basement membrane. Attached to the basement membrane are the keratinocytes, the actual skin cells. The keratinocytes capable of cell division are the basal cells, which are located closest to the basement membrane and continuously divide to form new cells. Older keratinocytes are pushed upward and flattened to form the stratified layers of the epithelium (malpighian layers). When these cells reach the outermost skin layer, the stratum corneum (horny layer), they are no longer living cells and are shed from the skin. Keratin, the protein produced by keratinocytes, makes the horny layer waterproof. A keratinocyte takes about 28 to 45 days to move from the basement membrane to the skin surface.

Vitamin D is activated in the epidermis by ultraviolet (UV) light, such as sunlight. It is then distributed by the blood to the intestinal tract, where it promotes uptake of dietary calcium.

Melanocytes are pigment-producing cells found at the basement membrane. These cells give color to the skin and account for the ethnic differences in skin tone. Darker skin tones are not caused by increased numbers of melanocytes; rather, the size of the pigment granules (melanin) contained in each cell determines the color. The purpose of melanin is to protect the skin from damage by UV light. For this reason, people with dark skin are less likely to develop sunburn than lighter-skinned people with the same sun exposure. Freckles, birthmarks, and age spots are caused by patches of melanin within the skin. UV light stimulates the production of melanin, which protects against the harmful effects of sun exposure. Melanin production increases in areas that have endocrine changes or inflammation.

Structure of the Skin Appendages

Hair, a thick protective pelt worn by most mammals, is mainly a cosmetic feature for modern humans. Hair growth varies with race, gender, age, and genetic predisposition. Individual hairs can differ in both structure and rate of growth, depending on body location.

Hair follicles are located in the dermal layer of the skin but are actually extensions of the epidermal layer (see Fig. 26-2). Within each hair follicle, a round column of keratin forms the hair shaft. Hair keratin is tougher than skin keratin. Hair color is genetically determined by a person’s rate of melanin production.

Hair growth occurs in cycles, with a growth phase followed by a resting phase. Stressors can alter the growth cycle and result in temporary hair loss. Permanent baldness, such as male pattern baldness, is inherited and is seldom influenced by personal or environmental factors.

Nails on fingers and toes have cosmetic value and are useful for grasping and scraping. Like hair follicles, the nails are extensions of the keratin-producing epidermal layers of the skin.

The white, crescent-shaped portion of the nail at the lower end of the nail plate is called the lunula and is the location of the nail matrix, where nail keratin is formed and nail growth begins (Fig. 26-3). Nail growth is a continuous but slow process. Fingernail replacement requires 3 to 4 months. Toenail replacement may take up to 12 months.

FIG. 26-3 Anatomy of the nail.

The cuticle, a layer of keratin at the nail fold, attaches the nail plate to the soft tissue of the nail fold. The nail body is translucent, and the pinkish hue reflects a rich blood supply beneath the nail surface. Nail growth and appearance are often altered during systemic disease or serious illness.

Sebaceous glands are distributed over the entire skin surface except for the palms of the hands and soles of the feet. Most of these glands are connected directly to the hair follicles (Fig. 26-4). The sebaceous glands of the eyelids, nipple areolae, and genitalia are freestanding.

FIG. 26-4 Anatomy of the hair follicle and sebaceous and sweat glands.

Sebaceous glands produce sebum, a mildly bacteriostatic, fat-containing substance. Sebum lubricates the skin and reduces water loss from the skin surface.

Sweat glands of the skin are of two types: eccrine and apocrine. Eccrine sweat glands arise from the epithelial cells. They are found over the entire skin surface and are not associated with the hair follicle. The odorless, colorless, isotonic secretions of these glands are important in the regulation of body temperature. Stimulation of sweat from these glands and the resultant water evaporation can cause the body to lose as much as 10 to 12 L of fluid in a single day.

Apocrine sweat glands are in direct contact with the hair follicle. They are found mostly in the axillae, nipple areolae, periumbilicus, and perineal body areas. The interaction of skin bacteria with the secretions of the apocrine glands causes the distinctive body odor.

Functions of the Skin

The skin is a complex organ responsible for the regulation of many body functions throughout the life span (Table 26-1) (McCance et al., 2010). In addition to the skin’s protective and regulatory functions, its location on the outside of the body makes it an important way to communicate a patient’s state of health and body image.

TABLE 26-1 FUNCTIONS OF THE SKIN

EPIDERMIS	DERMIS	SUBCUTANEOUS TISSUE
Protection
Keratin provides protection from injury by corrosive materials Inhibits proliferation of microorganisms because of dry external surface Mechanical strength through intercellular bonds	Provides fibroblasts for wound healing Provides mechanical strength Collagen fibers Elastic fibers Ground substance Sensory nerve endings signal skin injury and inflammation	Mechanical shock absorber Energy reserve Insulation
Homeostasis (Water Balance)
Low permeability to water and electrolytes prevents systemic dehydration and electrolyte loss	Lymphatic and vascular tissues respond to inflammation, injury, and infection	No real function in water balance
Temperature Regulation
Eccrine sweat glands allow dissipation of heat through evaporation of sweat secreted onto the skin surface	Cutaneous vasculature, through dilation or constriction, promotes or inhibits heat conduction from the skin surface	Fat cells act as insulators and assist in retention of body heat
Sensory Organ
Transmits a variety of sensations through the neuroreceptor system	Encloses an extensive network of nerve endings for relaying sensations to the brain	Contains large pressure receptors
Vitamin Synthesis
7-Dehydrocholesterol is present in large concentrations in malpighian cells, allowing photoconversion to active vitamin D	No function	No function
Psychosocial
Body image alterations occur with many epidermal diseases, such as generalized psoriasis	Body image alterations occur with many dermal diseases, such as scleroderma	Body image alterations may result from increases, decreases, and redistribution of body fat stores

Skin Changes Associated with Aging

The process of aging begins at birth. As changes in physiology progress with aging, the skin also undergoes age-related changes in both structure and function (Chart 26-1). Figs. 26-5 through 26-12 show some common age-related skin changes (Bianchi & Cameron, 2009).

Chart 26-1 Nursing Focus on the Older Adult

Changes in the Integumentary System Related to Aging

PHYSICAL CHANGES	CLINICAL FINDINGS	NURSING ACTIONS
Epidermis
Decreased thickness in epidermal layer	Increased skin transparency and fragility	Handle patients carefully to minimize friction and shear to the skin. Assess for excessive dryness or moisture. Avoid taping the skin.
Decreased epidermal mitotic activity	Delayed wound healing	Protect open areas; use moisture-retentive dressings to promote wound healing.
Decreased epidermal mitotic homeostasis	Skin hyperplasia, such as hyperkeratoses and skin cancers (especially in sun-exposed areas)	Assess non–sun-exposed areas to determine baseline skin features. Assess exposed skin areas for sun-induced changes.
Increased epidermal permeability	Increased susceptibility to irritant reactions	Teach patients how to avoid exposure to skin irritants.
Decreased number of Langerhans’ cells	Decreased cutaneous inflammatory response	Do not rely on redness and swelling to indicate skin damage.
Decreased number of active melanocytes	Increased sensitivity to sun exposure	Teach patients to wear hats and protective clothing. Teach patients to avoid sun exposure from 10 AM to 4 PM and to use sunscreen when outside.
Hyperplasia of melanocytes at the dermal-epidermal junction (especially in sun-exposed areas)	Mottled hyperpigmentation and hypopigmentation (e.g., liver spots, age spots)	Teach patients to keep track of such spots, but help them to differentiate these “normal” spots from those that need evaluation for malignancy.
Decreased vitamin D production	Increased susceptibility to osteomalacia	Urge patients to take a multiple vitamin or a calcium supplement that contains vitamin D.
Flattening of the dermal-epidermal junction	Increased susceptibility to shearing forces, with resultant blisters, purpura, skin tears, and pressure-related skin problems	Avoid pulling or dragging patients. Assist patients confined to bed or chairs to change positions at least every 2 hours. Avoid or use care when removing adhesive wound dressings.
Dermis
Decreased dermal blood flow	Increased susceptibility to dry skin (xerosis)	Teach patients to apply moisturizers when the skin is still moist and to avoid agents that promote skin dryness.
Decreased vasomotor responsiveness	Increased thermoregulatory alterations (predisposition to heat stroke and hypothermia)	Teach patients to dress for the environmental temperatures and not to rely on skin sensations to tell them they are too hot or too cold.
Decreased dermal thickness	Paper-thin, transparent skin with an increased susceptibility to trauma	Handle patients gently, and avoid the use of tape or tight dressings. Use lift sheets when positioning patients.
Degeneration of elastic fibers	Decreased tone and elasticity (wrinkles)	Use the forehead or chest to test skin turgor.
Benign proliferation of capillaries	Cherry hemangiomas	Teach patients that these are benign.
Reduced number and function of nerve endings	Alterations in sensory perception	Instruct patients to use bath thermometer and to lower the water heater temperature to prevent scalds.
Subcutaneous Layer
Thinning of subcutaneous fat layer	Increased susceptibility to hypothermia	Teach patients to dress warmly in cold weather and to wear hats and gloves when outdoors.
	Decreased resistance to mechanical injury (especially pressure necrosis)	Assist patients confined to bed or chairs to change positions at least every 2 hours.
Hair
Decreased number of hair follicles and rate of growth	Increased hair thinning	Suggest wearing hats in cold weather to prevent body heat loss and when in the sun to prevent burning the scalp.
Decreased number of active melanocytes in follicle	Gradual loss of hair color (graying)	Although associated with aging, inform patients that hair color loss can occur at any age.
Nails
Decreased rate of growth	Increased susceptibility to fungal infections	Inspect the nails (including toenails) of all older adults. Instruct patients to wear socks and to keep the feet clean, warm, and dry.
Decreased blood flow beneath the nail bed	Longitudinal nail ridges	Use the oral mucosa to assess for cyanosis.
Thickening of the nail	Toenails (especially) thicken and may overhang the toes	Use fingernails to assess capillary refill. Cut toenails straight across rather than on a curve. Do not use nail appearance alone to determine the presence of a fungal infection. Assess skin in contact with the nail to determine whether the thick nail is irritating it.
Glands
Decreased sebum production despite sebaceous gland hyperplasia	Increased size of pores (especially on nose); large comedones in malar region	Teach patients not to squeeze the pores or comedones to prevent traumatizing the skin.
Decreased eccrine and apocrine gland activity	Increased susceptibility to dry skin	Urge patients to avoid deodorant soaps and to use soaps with a high fat content. Teach patients to apply moisturizers immediately after bathing when skin is moist.
	Decreased perspiration, leading to decreased cooling effect	Do not use sweat production as an indicator of hyperthermia.

FIG. 26-5 Eyelid eversion, deepening of the eye orbit, and “bags” under the eye.

FIG. 26-6 Arcus senilis of the iris.

FIG. 26-7 Paper-thin, transparent skin with actinic lentigo (liver spots).

FIG. 26-8 Wrinkles.

FIG. 26-9 Graying and thinning of the hair.

FIG. 26-10 Xerosis (dry skin).

FIG. 26-11 Senile (cherry) angiomas.

FIG. 26-12 Nail changes: longitudinal ridges and thickening.

Individual differences exist in how quickly and to what degree the skin ages (Helfrich et al., 2008). Although genetic background, hormonal changes, and systemic disease may change the appearance of the skin over time, chronic sun exposure is the single most important factor leading to degeneration of the skin components.

Nclex Examination Challenge