Chapter 7: Integumentary System and Body temperature

sebaceous glands

(oil glands) are associated with hair follicles and are found in all areas of the body that have hair. They secrete an oily substance called sebum that flows into the hair root and then out onto the surface of the skin. Open directly onto the surface of the skin. The sebum lubricates and helps waterproof the hair and skin, as well as inhibits the growth of bacteria on the surface of the skin. With aging, sebum production decreases (dry skin, brittle hair).

Decreased Temperature

First, blood vessels constrict, heat is trapped in deeper tissues. Second, sweat glands become less active. Third, skeletal muscles contract, causing shivering. These three activities raise body temperature. Contraction of the arrector pili muscles causes goose bumps, indicating a decline in body temperature, but contributes minimally to heat production.

Hair color

Hair color is determined by the type and amount of melanin secretion. A lot of melanin=dark hair. Little melanin=light hair. With age, the melanocytes become less active; the absence of melanin produces white hair. Gray hair is causes by a mixture of pigmented and non pigmented hairs. Red hair is causes by a modified type of melanin that contains iron. Red heads require more anesthesia before surgery than people with other colored hair.

Hair growth

Hair growth and distribution are influenced by the sex hormones estrogen and testosterone. When a woman has too much testosterone, excessive hair growth occurs (hirsutism). Hair growth also responds rather well to mind-body signals.

Hair (forensically)

Hair is a gold mine. For example, arsenic is called inheritance powder because it is a long-time favorite for dispatching wealthy family members. Chronic arsenic poisoning is difficult to detect medically, but analysis of the hair not only detects the presence of arsenic; it can also detect the time course of the poisoning.

Heat production

Heat thermal energy is produced by the millions of chemical reactions occurring in the cells of the body. The heat is distributed throughout the body by the blood. The heat produced by metabolizing cells is the basis of body temperature. In the resting state, the greatest amount of heat is produced by the muscles, liver, and endocrine glands. The resting brain produces only about 15% of the heat. Interestingly, the studying brain does not produce much more heat. The amount of heat produced can be affected by many factors. The hormonal effects on heat production are dramatically illustrated by person with thyroid gland disease. The hypothyroid person generally has a lower-than-normal body temperature, but the hyperthyroid person has an elevated temperature. In fact, an extreme hyperthyroid state (thyroid storm) can elevate body temperature into a range that is potentially lethal.

Hair: Humans fear and coldness

Humans respond to fear and cold in the same way. Contraction of the arrector pili muscles also causes our hair to stand on end. As the hair stands, it pulls the skin up into little bumps. Unlike kitty, the erect human hair does not do much to trap heat.

Fever (pyrexia)

Increase in temperature. Pyrogenic cytokines, often secreted by pathogens, increase the hypothalamic set point (thermostat). Then, vasoconstriction (to conserve heat) and shivering (to produce heat) cause the body temperature to reach the elevated set point. The set point can be lowered, usually by resolving its cause (often infection) or by the use of a fever-lowering drug (aspirin) called an antipyretic. Then the body loses heat through vasodilation and sweating. Laypersons often describe this late phase as the "fever has been broken." A very high, life-threatening fever is called hyperpyrexia (105.8F or 41C).

Sudoriferous glands (sweat glands)

Located in the dermis. These glands secrete sweat; the sweat is secreted into a duct that opens onto the skin as a pore. An individual has about 3 million sweat glands. There are two types of sweat glands: apocrine and eccrine glands.

Hair loss

Loss of hair is called alopecia. This is caused by genes, or drug toxicity. As with chemotherapy or radiation therapy. Anticancer drugs are so cytotoxic that they often destroy hair-producing epithelial cells. When drug therapy is terminated, the cells regenerate and start to grow hair again.

Radiation

Means that heat is lost from a warm object (the body) to the cooler air surrounding the warm object. A person loses heat in a cold room.

Nails

Nails are thin plates of stratified squamous epithelial cells that contain a very hard form of keratin. The nails are found on the distal ends of the fingers and toes and protect these structures from injury.

Newborns and Body Temperature

Next to establishing respiratory activity, however, is the infant's need to regulate body temperature. In short, the neonate produces only about 2/3 of the heat produced by an adult, but loses twice as much.

Regulation

Normal body temperature is regulated by several mechanisms. The thermostat of the body is located in a part of the brain called the hypothalamus. The hypothalamus senses changes in body temperature and sends information to the skin (blood vessels and sweat glands) and skeletal muscle.

Body temperature

Normal body temperature is said to be 98.6F, although it can range from 97-100. The temperature fluctuates about 1.8F in a 24-hr period, being lowest in the morning and highest in the late afternoon. Body temperature also differs from one part of the body to another. The inner parts of the body (cranial, thoracic, and abdominal cavities) reflect the higher core temperature. The more surface areas (Skin and mouth) reflect the cooler shell temperature. For example, the rectal temperature measures core temperature and ranges between 99-99.7F, whereas the oral temperature is about 1F lower.

Evaporation

Occurs when a liquid becomes a gas. For example, during strenuous exercise, sweat on the surface of the skin evaporates and cools the body. Not that the evaporation of water is associated with a loss of heat. On a hot, humid day, water cannot evaporate from the surface of the skin. Hence, heat loss is diminished. This is why we feel that heat so intensely on a hot, humid day.

Blood

Pinkish color of fair skinned people? This is because so little melanin is produced that the blood in the dermal blood vessels is easily seen. Poorly oxygenated blood causes the skin to look blue (cyanosis). Embarrassment causes the blood vessels to dilate. This condition increases blood flow to the skin, causing the person to flush or blush.A person that is scared experiences a constriction of the blood vessels in the skin and a decrease in the amount of oxygenated blood. This results in a pale color (pallor). A black and blue discoloration (bruise) indicates that blood has escaped from the blood vessels into the injured tissue (ecchymosis).

Hypothermia

Refers to a decrease in body temperature and is usually caused by prolonged exposure to cold, as in falling through ice into cold water. Body temperature becomes to low for the body to sustain body metabolism. Death= below 96F or 35C

Hyperthermia

Refers to an elevation of body temperature cause by the inability of the body to get rid of excess heat; the body simply cannot cool itself. The cause of hyperthermia is environmental. For example, an infant left in a car on a hot day. Although, unlike fever, hyperthermia is not caused by resetting the thermostat; the set point is normal.

Newborns and Body Temperature

Several factors contribute to the excess heat loss: -The baby generally has a large surface area that increases heat loss (the curled up position of the infant decreases surface area and conserves heat.) Interestingly, considerable heat is lost from the head area; hence, the use of caps in the newborn nursery. -The baby generally has only a thin layer of subcutaneous fat. (Fat acts as an insulator, thus preventing heat loss.) -The neonate cannot shiver. So, it produces heat by a process called nonshivering thermogenesis. A neonate has brown adipose tissue (BAT), or brown fat, scattered throughout its body, especially around the neck and shoulder area. Metabolism of BAT generates more heat than the metabolism of ordinary adipose tissue (white fat). The heat produced by BAT is picked up by the blood and dispersed throughout the body.

Eschar

Severe burns are associated with eschar formation. Eschar is dead, burned tissue that forms a thick, inflexible, scalelike layer over the burned surface. Eschar is a problem for two reasons. First, it may surround an area, such as a leg, and act like a tourniquet, thereby cutting off the flow of blood to the extremity. More seriously, if the eschar surrounds the chest, it prevents chest expansion and breathing. Second, eschar, which is initially sterile, becomes a bleeding ground for bacteria and secretes potentially lethal toxins into the blood. Because eschar can have serious consequences, it is often slit to allow expansion of the burned area or removed to rid the body of a source of toxin.

Diet

Skin color may also change in response to diet. For example, it is possible to impart a yellow tint to the skin by overeating carotene-rich vegetables such as carrots.

Bilirubin

Skin color may also change in response to disease processes. A person with liver disease is unable to excrete a pigment called bilirubin. This pigment is instead deposited in the skin, causing it to turn yellow- a condition known as jaundice.

Hair (other functions)

Some areas of the hair perform other functions. For example, the eyelashes and eyebrows protect the eyes from dust and perspiration. The nasal hair trap dust and prevent it from being inhaled into the lungs. The hair of the scalp helps keep us warm.

sebaceous glands: Black heads and pimples

Sometimes, the sebaceous glands become blocked by accumulated sebum and other debris. When the sebum is exposed to the air and dries out, it turns black, forming a blackhead. When the blocked sebum becomes infected with staphylococci, it is a pimple. This formation is common among adolescents because sebaceous gland activity responds to the hormonal changes associated with puberty. Babies may also have a problem with their sebaceous glands. On the scalp, can over secrete sebum, producing oily scales. Because this condition occurs during infancy, the cradle period, it is called cradle cap.

Hair (how do we have hair?)

The chief parts of the hair are the shaft. Each hair arises from a group of epidermal cells that penetrate the dermis. This downward extension of epidermal cells forms the hair follicle. The epidermal cells of the hair follicle receive a rich supply of blood from the dermal blood vessels. As these cells divide and grow, the older cells are pushed toward the surface of the skin. As they move away from their source of nourishment, the cells die. Like other cells that compose the skin, the hair cells also become keratinized. The hair we have right now is a collection of of dead, keratinized cells.

Subcutaneous Layer (hypodermis)

The dermis lies above the subcutaneous layer. This layer is not considered part of the skin. This layer is composed primarily of loose connective and adipose tissue. It performs two main roles: it helps insulate the body from extreme temperature changes in the external environment, and it anchors the skin to the underlying structures. A few areas of the body have no subcutaneous layer and the skin anchors directly to the bone. (The knuckles, wrinkled and creased because it attaches directly to the bone).

Layers of the skin: Epidermis

The epidermis is the thin outer layer of the skin and is composed of stratified squamous epithelium. The epidermis is avascular; it has no blood supply of its own. Oxygen and nutrients diffuse into the lower epidermis from the rich supply of blood in the underlying dermis. Can be divided into 5 layers. Two of the layers are deeper stratum germinativum and the more superficial stratum corneum.

When skin is burned

The extent of the burn injury is initially evaluated according to the rule of nines. In this system, the total body surface area is divided into regions. The assigned percentages are related to the number 9. For example, the head and beck are considered to be 9% of the total body surface area. Each upper limb is 9%, whereas each lower limb is 18% (9x2). To determine proper treatment, the clinician needs to elevate and depth and extent of the burn injury.

Modified sweat glands

The mammary glands are located in the breasts and secrete milk. The ceruminous glands are found in the external auditory canal of the ear. They secrete cerumen, or ear wax. Repels insects and traps foreign material. Some dyes, foods, and drugs are excreted in the sweat and may color the sweat in a variety of bright hues. (chromhidrosis).

sebaceous glands: fetus

The sebaceous glands play a unique role in the fetus. Babies are born with a covering that resembles cream cheese. The covering is called the vernix caseosa and is secreted by the sebaceous glands. This protects the skin of the fetus from the macerating effects of amniotic fluid.

The skin, drugs, and chemicals

The skin can absorb many chemicals; this is good news and bad news. The good news is concerned with drug absorption. Drugs could be placed on the skin and absorbed transdermally (across the skin) to achieve a systemic effect (throughout the body). The bad news is skin can absorb toxins; these include pesticides, cleaning fluids, the action in nail polish remover, mercury, and many other toxic chemicals that we encounter everyday.

Structure of the skin

The skin is called the integument or cutaneous membrane and is considered an organ; it is the largest organ in the body. The skin has 2 distinct layers- the outer, or surface, layer is the epidermis and the inner layer is the dermis. The dermis is anchored to a subcutaneous layer. The study of skin and skin disorders is referred to as dermatology.

Accessory Structures of the Skin

The skin is the home of several accessory structures including the hair, nails, and glands.

Sum it up:

The skin is the home of several structures, including the hair, nails, and glands. There are two major exocrine glands: the sebaceous glands and the sweat glands (sudoriferous). There are two types of sweat glands: the eccrine glands and the apocrine glands. Modified sweat glands include the ceruminous glands, which secrete ear wax, and the mammary glands, which secrete milk.

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The skin mirrors your stress level. How many times have you become stressed out and then broke out?

Skin care for older people

The skin of an older person is normally drier, more easily injured, and slower to heal. Because the skin is so dry, excessive use of soap should be discouraged. Moreover, maintaining the acid surface of the skin discourages the growth of bacteria. Both the dermis and underlying subcutaneous layer become thinner. As a result, older people bruise more easily because the blood vessels are not well protected. Also, heat is lost from the blood vessels, so older people often feel cold.

Vagabond Syndrome

The skin of people who continuously harbor body lice becomes hardened and darkly pigmented. Chronic infestation of lice also causes the person to feel tired and irritable.

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The skin responds to chronic irritation. Epidermal cells growth increases in response to certain stimuli. For example, constant irritation or rubbing or an area causes the rate of epidermal cell division to increase, producing a thickened area called "callus". Constant rubbing overgrowth of epidermal cells arranged in a conical shape. This overgrowth is called "corn".

What forms the integumentary system?

The skin, its accessory structures (sweat glands, oil glands, hair, and nails), and the subcutaneous tissue below the skin form the integumentary system.

The eccrine glands

The sweat secreted by the eccrine glands play an important role in body temperature regulation. As sweat evaporates from the skin surface, heat is lost. These are the glands that sweat profusely on hot days or during periods of strenuous exercise. The glands function throughout an entire lifetime. Secretion is composed primarily of water and a few salts.

Fingerprints

The wavy boundary between the epidermis and dermis resembles the ridges of corrugated cardboard. The interlocking ridges prevent the slippage of the skin layers. The ridges also form the fingerprints. An adults fingerprints are oil-based. A child's fingerprints are water-based. Therefore, when the water evaporates, so does the fingerprints.

Carotene

The yellowish tint of carotene in most persons is hidden by the effects of melanin. Because people of Asian descent have little melanin in their skin, the carotene gives their skin a yellow tint.

Layers of the skin: Dermis

This layer is located beneath the epidermis and is the largest portion of the skin; it is composed of dense fibrous connective tissue. It contains numerous collagen and elastin fibers surrounded by a gel like substance. (Skin stretching during pregnancy and weight gain). Excessive stretching causes small tears in the skin called stretch marks or striae. The thickness of the epidermis and dermis varies according to the location on the body.

Epidermis: Stratum corneum

This layer is the surface layer of the epidermis and is composed of about 30 layers of dead, flattened, keratinized cells. The dead cells are always sloughed off, exfoliated, or desquamated through wear and tear. The dead sloughed cells are called "dander"; when dander is clumped together by the oil in the skull, it is called "dandruff". The sloughed cells are replaced by other cells that are constantly moving up from the deeper layers. You shed about 40,000 skin cells each minute, each month you have a new layer of epithelium. (fun fact: tattoos must go through to the dermis because epidermis sheds too much).

Epidermis: Stratum germinativum

This layer lies on top of the dermis and thus has access to a rich supply of blood. The cells of this layer are always dividing, producing millions of cells per day. As the cells divide, they push the older cells towards the surface of the epithelium. As the cells move away from the dermis, two changes take place. First, as they move away from their source of nourishment, the cells begin to die. Second, the cells under go a process of keratinization, whereby a tough protein, keratin, is deposited within the cell. The keratin hardens and flattens the cells as they move toward the surface of the skin. In addition, the keratin makes the skin water-resistant.

Normothermia

This refers to the normal range of the body temperature from 97 to 99.6F (36.1 to 37.6C)

Hair

Today, Most of the hair covering our bodies is sparse (thin), and very fine with the exception of the hair on our heads. The main function of our sparse hair is to sense insects on the skin before they could sting us.

Glands

Two major exocrine glands are associated with the skin: the sebaceous glands and the sweat glands.

Melanin

When exposed to the ultraviolet radiation of sunlight, the melanocytes secrete more melanin. The skin darkens in an attempt to protect the deeper layers from the harmful effects of radiation (Summer tan). If melanocytes fail to secrete melanin, the skin, hair, and the colored part of the eyes (iris) are white (Albinism) Other persons develop a condition called vitiligo, this involves a loss of pigment in certain areas of the skin, creating patches of white skin. Melanin can also stain unevenly. Freckles and moles are examples of melanin that becomes concentrated in local areas.

Skin Color

Why are there different colors of the skin? Skin color is determined by many factors: some genetic, some physiological, and some caused by disease. Deep within the epidermal layer of the skin are cells called "melanocytes". They secrete a skin-darkening pigment called "melanin"; the melanin stains the surrounding cells, causing them to darken. The more melanin, the darker your skin. We all have the same number of melanocytes, what determines our color of skin is the amount of melanin secreted.

Increased Temperature

With exercise and temperature elevation, the blood vessels dilate, thereby allowing more blood to flow to the skin. This transfers heat from the deeper tissues to the surface of the body. It then gives a flushed appearance. Sweat evaporates with the heat, then heat is lost.

The eccrine glands

are the more numerous and widely distributed of the sweat glands. They are located throughout the body and are especially numerous on the forehead, neck, back, upper lip, palms, and soles. Not associated with hair follicles.

Apocrine gland

are usually associated with hair follicles and are found in the axillary and genital areas. They respond to emotional stress and become more active when the person is frightened, upset, in pain, or sexually excited. Because the development of these glands is stimulated by the sex hormones, they become more active during puberty. The sweat produced by these glands does not have a strong odor. If allowed to accumulate on the skin, however, the substances in sweat are degraded by bacteria into the chemicals with a strong unpleasant odor. This is called body odor and is the reason why we use deodorant. Some of these secretions act as sex attractants. These sex attractants are called pheromones. The vaginal secretions of an ovulating female contain pheromones called copulines. These can cause a testosterone surge in the male.

The nails tell a story

clubbing: chronic lung and heart disease cause clubbing, a condition that indicates that the fingertips have received an insufficient supply of oxygenated blood over a period of time. The fingertips enlarge, and the nails become thick, hard, shiny, and curved at the free end. May detach from its base. In the pink...or not: Nail color should be pink. Poor oxygenation makes the blood appear bluish-red (cyanosis), which in turn makes the nails appear bluish. Other color changes include pigment bands; these dark bands are normally seen in dark-skinned individuals. When present in light-skinned persons, the bands may indicate melanoma. Brittle: Nails may also be described as brittle; this is generally caused by poor oxygenation, thyroid gland dysfunction, and nutritional anemia.

Convection

is the loss of heat by air currents moving over the surface of the skin. For example, a fan moves air across the surface of the skin, thereby constantly removing the layer of heated air next to the body.

Conduction

is the loss of heat from a warm body to a cooler object in contact with the warm body. For example, a person (warm object) becomes cold when sitting on on a block of ice (cooler object). Clinically, a cooling blanket may reduce a dangerously high fever.

Body temperature

maintained by balancing heat production and heat loss. The mechanism whereby the body balances heat production and heat loss is called thermoregulation. Failure to thermoregulate causes body temperature to fluctuate; an excessive decrease in body temperature is called hypothermia, and an excessive increase is called hyperthermia.

Functions of the integumentary System

-Acts as a mechanical barrier. It keeps harmful substances out of the body and helps retain water and electrolytes. The acid pH of the skin surface serves as a protective chemical barrier. -Protects the internal structures and organs from injuries caused by blows, cuts, harsh chemicals, sunlight, burns, and pathogenic microorganisms. -Participates in the immune response against invading microbes by housing specialized cells, called dendritic or Langerhans' cells. When the skin is broken, the dendritic cells alert the immune system so that it can ward off infection. -Performs an excretory function. Although excretion is a minor role, the skin is able to excrete water, salt, and small amounts of waste, such as urea. -Acts as a gland by synthesizing vitamin D when exposed to sunlight. Vitamin D is necessary for the absorption to calcium from the digestive tract. -Performs a sensory role by housing the sensory receptors for touch, pressure, pain, and temperature. In this way, the skin helps detect information about the environment. -Play an important role in the regulation of body temperature.

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-The skin reflects disease processes in the body. For example, a person with shingles, an inflammation of nerves cause by the chickenpox virus- develops painful skin lesions along the path of the nerve. A person with a severe generalized staphylococcal infection may develop scalded skin syndrome, a condition in which the skin appears scalded and feels off in layers. Many clinical disorders present initially with skin rashes; the rashes offer clues to the underlying problems.

As you age

1. aging causes a generalized thinning of the epidermis and epidermal cells reproduce more slowly and are larger and more irregular. These changes result in thinner, more translucent skin. 2. melanocyte activity decreases, resulting in decreased protection from ultraviolet light and greater susceptibility to sunburn and skin cancer. Selected melanocytes increase melanin production, resulting in brown spots, or age spots. 3. the dermis becomes thinner, with a decreased amount of collagen and decreased number of elastin fibers. The result is increased fragility of the skin, as well as increased wrinkles. The skin also heals more slowly. 4. there is a decreased number of dermal blood vessels with a slower rate of repair. This change causes the skin to become more susceptible to small hemorrhage and pressure ulcers. 5. Blood vessels in the subcutaneous tissue decreases, so drugs administered subcutaneously are absorbed more slowly. 6. The amount of adipose tissue in the subcutaneous layer decreases, resulting in increased and wrinkled skin that has a decreased ability to maintain body temperature. The person tends to feel cold. 7. Sebaceous gland activity decreases, resulting in decreased ability to regulate body temperature and intolerance to cold. 8. Sweat gland activity decreases, resulting in decreased ability to regulate the body temperature and intolerance to cold. 9. The rate of melanin production by the hair follicle decreases. As a result, hair may become lighter in color, turning gray or white. Hair does not replace itself as often and becomes thinner. 10. Blood supply to the nail bed decreases. Consequently, the nails can become dull, brittle, hard, and thick; their growth rate also slows.

The skin tells a story:

4 next sections

Heat loss

80% of heat loss occurs through the skin. The remaining 20% is lost through the respiratory system and in the excretory products (urine and feces). Heat loss occurs by four means: Radiation, conduction, convection, and evaporation.

Why perspiration is sensible or insensible

About 500mL/day of water is normally lost through the skin and is called insensible perspiration. If the epidermis is damaged, as in severe burns, the rate of insensible perspiration increases enormously; the fluid loss is so great that the untreated patient may die from shock because of low blood volume. The eccrine glands are responsible for sensible perspiration. As body temperature rises, as in exercise, the eccrine glands increase the secretion of sweat, thereby cooling the body. When operating maximally, the eccrine glands can secrete 1 gallon of sweat per hour in an attempt to cool the body.

Dermis Layer (continued)

Although derived from the epidermis, the accessory structures such as the hair, nails, and certain glands are embedded within the dermis. Also located within the dermis are blood vessels, nervous tissue, and some muscle tissue. Many of the nerves have specialized endings called "sensory receptors" that detect pain, temperature, pressure, and touch.

Hair: Frightened kitty

Attached to the hair follicle is a group of smooth muscle cells called the arrector pili. Contraction of these muscles causes the hair to stand on end. When frightened, the cat's brain sends its panic message along the nerves to these muscles. The muscles then contract and pull the hair into an upright position. Her fur also stands on end when she is cold, the raised fur traps heat and helps her stay warm.

When skin is burned

Burns are classified according to the depth of the burn and the extent of the surface area burned. On the basis of depth, turns are classified as partial thickness burns or full-thickness burns. Partial- thickness burns are further divided into first-degree and second-degree burns. The first degree burn is red, painful, and slightly edematous (swollen). Only the epidermis is involved. A second-degree burn involves damage to both the epidermis and the dermis. With little damage to the dermis, the symptoms of a second-degree burn include redness, pain, edema, and blister formation. With greater damage to the dermis, the skin may appear red, tan, or white. Full-thickness burns are also called third-degree burns. With a burn this severe, both the epidermis and dermis are destroyed, often with destruction of the deeper underlying layers. Third-degree burns are painless because the sensory receptors have been destroyed. May appear white, tan, brown, black, or deep cherry red.

Hair shape

Curly, wavy, or straight- this is determined by the shape of the hair shaft. A round shaft produces straight hair, oval shaft produces wavy hair, and curly hair is a result of flat hair shafts.

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Drug reactions are often revealed by skin changes. For example, a person allergic to penicillin may develop hives, or urticaria. Similarly, a person allergic to sulfa drugs may develop a generalized rash that can process to a lethal syndrome called "Stevens-Johson syndrome".

Nail structure

Each nail has the following structures: a free edge, a nail body (fingernail), and a nail root. The cells of the nail body develop and are keratinized in the nail root. The extent of nail growth is represented by the half-moon-shaped lunula, located at the base of the nail. As the nail body grows, it slides over a layer called the nail bed, a part of the epidermis. The pink color of nails is caused by the blood vessels in the underlying dermal layer beneath the nail. The cuticle is a fold of stratum corneum that grows onto the proximal portion of the nail body.