Chapter 5 Anatomy and Physiology

FIGURE 5.16 Effects of Sunlight on Skin.

(a) A 91-year old Japanese monk who has spent most of his life indoors. (b) A 62-year old Native American woman who has spent most of her life outdoors.

Which cells of the epidermis produce melanin? What happens to the melanin once it is produced?

1. Melanosomes are produced by the Golgi apparatus of the melanocyte. 2. Melanosomes move into melanocyte cell processes. 3. Epithelial cells phagocytize the tips of the melanocyte cell processes. 4. The melanosomes, which were produced inside the melanocytes, have been transferred to epithelial cells and are now inside them.

What are some of the major functions of the integumentary system?

1. Protection 2. Sensation 3. Temperature regulation. 4. Vitamin D production. 5. Excretion.

Describe the general functions of the integumentary system.

1. Protection 2.Sensation 3.Temperature regulation 4.Vitamin D production 5.Excretion

What happens during the growth stage?

1.During the growth stage, a hair increases in length as new matrix cells are produced, differentiate, become keratinized, and die. 2.The hair grows longer as cells are added at the base of the hair root. 3.Eventually, hair growth stops; the hair follicle shortens and holds the hair in place. 4.A resting period follows, after which a new cycle begins.

How is sweat produced by eccrine sweat glands?

1.The coiled part of the gland produces an isotonic fluid that is mostly water but also contains some salts (mainly sodium chloride) and small amounts of ammonia, urea, uric acid, and lactic acid. 2.As this fluid moves through the duct, sodium chloride moves by active transport from the duct back into the body, thereby conserving salts. 3. The resulting hyposmotic fluid that leave the duct is called sweat.

What causes the skin to sag and wrinkle?

A decrease in the number of elastic fibers in the dermis and a loss of adipose tissue from the subcutaneous tissue cause the skin to sag and wrinkle.

What develops and grows with hair follicles?

A hair develops and grows within each hair follicle.

What is a moderate burn?

A moderate burn is a third-degree burn over 2 - 10% of the BSA or a second-degree burn over 15-25% of the BSA.

What does a nail consist of?

A nail consists of the proximal nail root and the distal nail body.

Can baldness occur in women?

Although baldness is more common and more pronounced in certain men, it can also occur in women.

What can prevent the manufacture of melanin?

Although many genes are responsible for skin color, a single mutation can prevent the manufacture of melanin.

What is an important difference between thick and thin skin?

Another important difference between thick and thin skin is that hair is found only in thin skin.

Why are sebaceous glands classified as holocrine glands?

Because sebum is released by the lysis and death of secretory cells, sebaceous glands are classified as holocrine glands.

What is the hyponychium?

Beneath the free edge of the nail body is the hyponychium, a thickened region of the stratum corneum.

What hair has the most melanin?

Blonde hair has little black-brown melanin, whereas jet black hair has the most.

PROCESS FIGURE 5.10 Heat Exchange in the Skin

Blood transfers heat from deeper tissues to the surface of the skin, where the heat is lost. Atleration of blood vessel diameter, and therefore blood flow, allows for regulation of heat loss at the skin.

What is body temperature affected by?

Body temperature is affected by blood flow through the skin. When blood vessel in the dermis dilate, more warm blood flows from deeper structure to the skin, and heat loss increases. Body temperature tends to increase as a result of exercise, fever, or a rise in environmental temperature. In order to maintain homeostasis, this excess heat must be lost.

FIGURE 5.15 Systems Interactions: Burns

Burns affect more than just the skin. This diagram illustrates how the systems of the body are affected following a burn.

What is carotene?

Carotene is a yellow pigment found in plants, such as carrots and corn.

Can carotene change your skin color?

Carotene is lipid-soluble and, when large amounts of carotene are consumed, the excess accumulates in the stratum corneum and in adipocytes of the dermis and subcutaneous tissue, causing the skin to develop a yellowish tint. The yellowish tint slowly disappears once carotene intake is reduced.

What is deep to the skin?

Deep to the skin is the subcutaneous tissue.

What is the ABCDE rule?

Early detection and treatment of melanoma before it metastasizes can prevent death. Melanoma can be detected by routine examination of the skin and application of the ABCDE rule, which states the signs of melanoma: -A stands for asymmetry (one side of the lesion does not match the other side), -B is for border irregularity (the edges are ragged, notched, or blurred), -C is for color (pigmentation is not uniform), -D is for diameter (greater than 6 mm), and -E is for evolving (lesion changes over time). Evolving lesions change size, shape, elevation, or color; they may bleed, crust, itch, or become tender.

Where are eccrine sweat glands found?

Eccrine sweat glands are distributed over the majority of the areas of the body but are most numerous in the palms of the hands and soles of the feet. Eccrine sweat glands are not found on the margin of the lips, the labia minor, and the tips of the penis and clitoris.

What are eccrine sweat glands?

Eccrine sweat glands are the most common type of sweat gland. They are simple, coiled, tubular glands that open directly onto the surface of the skin through sweat pores.

How are eccrine sweat glands divided?

Eccrine sweat glands can be divided into two parts: (1) the deep, coiled portion, which is located mostly in the dermis; and (2) the duct, which passes to the skin surface.

Keratinocytes

Epidermal cell that produces keratin.

What are some examples of types of skin color changes?

Erythema and cyanosis are examples of these types of skin color changes.

Erythema

Erythema is a condition in which the skin turns a reddish hue when the amount of blood flowing through the skin increases.

What is excretion?

Excretion is the removal of waste products from the body.

Lanugo

Fine, soft, unpigmented fetal hair.

What is hair controlled by?

Hair color is controlled by several genes, and dark hair color is not necessarily dominant over light.

What do desmosomes hold together?

In addition, desmosomes hold the keratinocytes together.

What are the arrector pili muscle contractions important for in mammals?

In other mammals, arrector pili muscle contractions are important for warmth as well as communication of aggression or fear.

What is stratum basale made of?

It is a single layer of cuboidal or columnar cells.

How else are skin cells shed?

Less noticeably, skin cells are continually shed from other areas as clothes rub against the body or as the skin is washed.

What is melanin?

Melanin is the group of pigments primarily responsible for skin, hair, and eye color.

Stratum corneum

Most superficial layer of the epidermis consisting of flat, keratinized, dead cells.

Epidermis

Outer portion of the skin formed of epithelial tissue that rests on or covers the dermis.

Cuticle

Outer, thin layer, usually horny--for example, the outer covering of hair or the growth of the stratum corneum onto the nail.

How is red hair caused?

Red hair is caused by varying amounts of a red type of melanin.

FIGURE 5.8 Glands of the Skin

Sebaceous glands and apocrine sweat glands empty into a hair follicle. Eccrine sweat glands empty onto the surface of the skin.

How is skin classified?

Skin is classified as thick or thin based on the structure of the epidermis.

How does the body regulate temperature?

The body accomplishes this by producing sweat. The sweat spreads over the surface of the skin; as it evaporates, the body loses heat.

What is performed to prevent complications in healing from deep partial-thickness and full-thickness burns?

To prevent these complications and speed healing, skin grafts are performed.

What are vellus hairs?

Vellus hairs, which are short, fine, and usually unpigmented, replace the lanugo on the rest of the body.

FIGURE 5.9 Nail

(a) Dorsal view of the exterior nail. (b) Cross section the nail. (c) Longitudinal section of the nail.

FIGURE 5.11 The Rule of Nines

(a) In an adult, surface areas can be estimated using the rule of nines; Each major area of the body is 9%, or a multiple of 9%, of the total body surface area. (b) In infants and children, the head represents a larger proportion of surface area, so the rule of nines is not as accurate, as can be seen in this depiction of a 5-year-old child.

FIGURE 5.2 Dermis and Epidermis

(a) Photomicrograph of the dermis covered by the epidermis. The dermis consists of the papillary and reticular layers. The papillary layer has projections, called papillae, that extend into the epidermis. (b) Higher-magnification photomicrograph of the epidermis resting on the papillary layer of the dermis. Note the strata of the epidermis.

FIGURE 5.7 Hair Follicle

(a) The hair follicle contains the hair and consists of a dermal and an epithelial root sheath. (b) Enlargment of the hair follicle wall and hair bulb. (c) Cross section of a hair within a hair follicle.

How does the skin help regulate body temperature?

1. Blood vessel dilation results in increased blood flow toward the surface of the skin. 2. Increased blood flow beneath the epidermis results in increased heat loss (gold arrows). 3. Blood vessel constriction results in decreased blood flow toward the surface of the skin. 4. Decreased blood flow beneath the epidermis results in decreased heat loss.

List the steps of heat exchange in skin?

1. Blood vessel dilation results in increased blood flow toward the surface of the skin. 2. Increased blood flow beneath the epidermis results in increased heat loss (gold arrows). 3. Blood vessel constriction results in decreased blood flow toward the surface of the skin. 4. Decreased blood flow beneath the epidermis results in decreased heat loss.

What are the steps of keratinization?

1. In the stratum basal, cells divide by mitosis, and some of the newly formed cells become the cells of the more superficial strata 2. In the stratum spinous, keratin fibers and lamellar bodies accumulate 3. In the stratum granulosum, keratohyalin granules accumulate, and a hard protein envelope forms beneath the plasma membrane; lamellar bodies release lipids; cells die. 4. In the stratum lucidum, the cells are dead and contain dispersed keratohyalin. 5. In the stratum corneum, the dead cells have a hard protein envelope, contain keratin, and are surrounded by lipids.

From deepest to most superficial, name and describe the five strata of the epidermis. In which stratum are new cells formed by mitosis? Which strata have live cells, and which strata have dead cells?

1. In the stratum basale, cells divide by mitosis, and some of the newly formed cells become the cells of the more superficial strata. 2. In the stratum spinousum, keratin fibers and lamellar bodies accumulate 3. In the stratum granulosum, keratohyalin granules accumulate, and a hard protein envelop forms beneath the plasma membrane; lamellar bodies release lipids; cells die. 4. In the stratum lucidum, the cells are dead and contain dispersed keratohyalin. 5. In the stratum corneum, the dead cells have a hard protein envelope, contain keratin, and are surrounded by lipids.

List the steps of Melanin transfer to keratinocytes.

1. Melanosomes are produced by the Golgi apparatus of the melanocyte. 2. Melanosomes move into melanocyte cell processes. 3. Epithelial cells phagocytize the tips of the melanocyte cell processes. 4. The melanosomes, which were produced inside the melanocytes, have been transferred to epithelial cells and are now inside them.

What is a burn?

A burn is injury to a tissue caused by heat, cold, friction, chemicals, electricity, or radiation.

How is cyanosis produced?

A decreases in blood flow, as occurs in shock, can make the skin appear pale, and decrease in the blood oxygen content produces cyanosis.

What sebaceous glands are not associated with hairs?

A few sebaceous glands located in the lips, the eyelids (meibomain glands), and the genitalia are not associated with hairs but open directly onto the skin surface.

What does a hair follicle consist of?

A hair follicle consists of a dermal root sheath and epithelial root sheath.

How is the hair divided?

A hair is divided into the shaft, which protrudes above the surface of the skin, and the root, located below the surface. The base of the root is expanded to form the hair bulb.

What are the regions of a hair? What type of cells make up most of a hair?

A hair is divided into the shaft, which protrudes above the surface of the skin, and the root, located below the surface. The base of the root is expanded to form the hair bulb. Most of the root and the shaft are composed of columns of dead, keratinized epithelial cells arranged in three concentric layers: (1) the medulla, (2) the cortex, and (3) the cuticle. The medulla is the central axis of the hair, and it consists of two or three layers of cells containing soft keratin. The cortex surrounds the medulla and forms the bulk of the hair. The cells of the cortex contain hard keratin. The cortex is covered by the cuticle, a single layer of cells also containing hard keratin. The edges of the cuticle cells overlap like shingles on a roof.

What is a minor burn?

A minor burn is a third-degree burn over less than 2% or a second-degree burn over less than 15% of the BSA.

What is a nail?

A nail is a thin plate consisting of layers of dead stratum corneum cells that contain a very hard type of keratin.

Name the parts of a nail. What part produces most of the nail? What is the lunula?

A nail is a thin plate consisting of layers of dead stratum corneum cells that contain a very hard type of keratin. Nails are located on the distal ends of the digits (fingers or toes). A nail consists of the proximal nail root and the distal nail body. The nail root is covered by skin, and the nail body is the visible portion of the nail. The lateral and proximal edges of the nail are covered by skin called the nail fold, and the edges of the nail are held in place by the nail groove. The stratum corneum of the nail fold grows onto the nail body as the cuticle, or eponychium. beneath the free edge of the nail body is the hyponychium, a thickened region of the stratum corneum. The nail root extends distally from the nail matrix. The nail also attaches to the underlying nail bed, which is located between the nail matrix and the hyponychium. The nail matrix and bed are composed of epithelial tissue, with a stratum basale that gives rise to the cells that form the nail. Though both contribute to the growth of the nail, the nail matrix is thicker than the nail bed and appears pink because of blood vessels in the underlying dermis. A small part of the nail matrix, the lunula, is seen through the nail body as a whitish, crescent-shaped area at the base of the nail. The lunula, seen best on the thumb, appears white because the blood vessels do not show through the thicker nail matrix.

What is the lunnula?

A small part of the nail matrix, the lunnula is seen best on the thumb, appears white because of the blood vessels do not show through the thicker nail matrix.

What is a solution to the body rejecting skin from other animals?

A solution to this problem is laboratory-grown skin. A piece of healthy skin from he burn victim is removed and paced into flask with nutrients and hormones that stimulate rapid growth. The skin that is produced consists only of epidermis and does not contain glands or hair.

Subcutaneous injection

A subcutaneous injection extends into the subcutaneous tissue; an insulin injection is one example. A subcutaneous injection is achieved by pinching the skin to form a "tent," into which a short needle is inserted.

What does each strata in thin skin contain?

Additionally, each strata in thin skin contains fewer layers of cells than are found in thick skin.

What is albinism?

Albinism is usually a recessive genetic trait that results from an inability to produce tyrosinase. The result is a deficiency or an absence of pigment in the skin, the hair, and the irises of the eyes.

What is alopecia areata?

Alopecia areata, often called spot baldness, involves varying degrees of hair loss and can affect all areas of the body.

What causes Erythema?

An inflammatory response stimulated by infection, sunburn, allergic reactions, insect bites, or other causes can produce erythema. Exposure to the cold and blushing or flushing when angry or hot can also produce erythema.

Intradermal injection

An intradermal injection, as is used for the tuberculin skin test, goes into the dermis. It is administered by drawing the skin taut and inserting a small needle at a shallow angle into the skin.

Intramuscular injection

An intramuscular injection reaches a muscle deep to the subcutaneous tissue. Intramuscular injections are used for injecting most vaccines and certain antibiotics.

What kind of keratin is found in the external parts of hair and in the nails?

Another type of keratin, hard keratin, is found in nails and the external parts of hair.

Where are apocrine sweat glands found?

Apocrine sweat glands are found in the axillae and genitalia (scrotum and labia majora) and around the anus.

What are apocrine sweat glands?

Apocrine sweat glands are simple, coiled, tubular glands that usually open into hair follicles superficial to the opening of the sebaceous glands.

How do apocrine sweat glands become active?

Apocrine sweat glands become active at puberty as a result fo sex hormones. Their secretions contain organic substances, such as 3-methyl-2-hexenoic acid, that are essentially odorless when first released but are quickly metabolized by bacteria to cause what is commonly known as body odor. Many mammals use scent as a means of communication, and physiologists have suggested that the activity of apocrine sweat glands may signal sexual maturity.

How much of the bodies lipids are in the subcutaneous tissue?

Approximately half the body's stored lipids are in the subcutaneous tissue, where they function in insulation and padding and as a source of energy.

What is the process of keratinization?

As keratinocytes move from the deeper epidermal layers to the surface, the cells change shape and chemical composition, through the process called keratinization, where the cells accumulate keratin.

What happens as keratinocytes progress through this stratum?

As keratinocytes progress through the stratum, additional keratin fibers and lipid-filled, membrane-bound organelles called lamellar bodies form inside the cells.

What happens when new keratinocyte cells are formed?

As new cells form, they push older cells to the surface, where they slough off.

Why is the skin more easily damaged as the body ages?

As the body ages, the skin is more easily damaged because the epidermis thins and the amount of collagen in the dermis decreases.

Compared with young skin, why is aged skin more likely to be damaged, wrinkled, and dry?

As the body ages, the skin is more easily damaged because the epidermis thins and the amount of collagen in the dermis decreases. Skin infections are more likely, and the skin repair occurs more slowly. A decrease in the number of elastic fibers in the dermis and a loss of adipose tissue from the subcutaneous tissue cause the skin to sag and wrinkle.

What happens when the cells of stratum spinousum are pushed to surface?

As the cells in this stratum are pushed to the surface, they flatten; desmosomes break apart, and new desmosomes form.

What happens as the nail forms?

As the nail forms in the nail matrix and bed, it slides over the nail bed toward the distal end of the digit.

What causes different shades of hair color?

As with the skin , varying amounts and types of melanin cause different shades of hair color.

What is associated with hair follicles?

Associated with each hair follicle are smooth muscle cells called the arrector pili.

Explain the location and action of arrector pili muscles.

Associated with each hair follicle are smooth muscle cells called the arrector pili. The arrector pili extend from the dermal root sheath of the hair follicle to the papillary layer of the dermis. Normally, the hair follicle and the hair inside it are at an oblique angle to the surface of the skin. When the arrector pili muscles contract, however, they pull the follicle into a more perpendicular position, causing the hair to "stand on end." Movement of the hair follicles produces raised areas called "goose bumps." This is a common response to cold temperatures as well as strong emotional responses. In other mammals, arrector pili muscle contractions are important for warmth as well as communication of aggression or fear.

What stage are scalp hairs in?

At any given time, an estimated 90% of the scalp hairs are in the growing stage. It is normal for a person to lose approximately 100 scalp hairs per day.

How are secretions released from sweat glands?

At one time, physiologists believed that secretions were released in a merocrine fashion from eccrine glands and in an apocrine fashion from apocrine glands. But we now know that apocrine sweat glands also release some of their secretions in a merocrine fashion, and possibly some in a halocrine fashion. Traditionally, they are still referred to as apocrine sweat glands.

What replaces vellus hair and when?

At puberty, terminal hair, especially in the pubic and axillary regions, replaces much of the vellus hair.

What is found at the opening of the follicle?

At the opening of the follicle, the external epithelial root sheath has all the strata found in thin skin.

What anchors the epidermis to the basement membrane?

At the stratum basale, the epidermis is anchored to the basement membrane by hemidesmosomes.

Stratum basale

Basal, or deepest, layer of the epidermis; also called stratum germinativum.

What can result from fourth-degree burns?

Because of the severity of tissue damage, fourth-degree burns often require amputation or removal of damaged tissue. Death may occur due to the increased likelihood of infection.

Explain why a "paper cut" may not bleed.

Because paper may not cut through all layers of the skin.

What makes a nail hard? Do nail have growth stages?

Beneath the free edge of the nail body is the hyponychium, a thickened region of the stratum corneum. Nails grow at an average rate of 0.5 - 1.2 mm per day, and fingernails grow more rapidly than toenails. Unlike hair, they grow continuously through life and do not have a resting place.

How are burns classified?

Burns are classified according to the extent of surface area involved and the depth of the burn.

How do burns of joints heal?

Burns of joints often heal with scar tissue formation that limits movement.

Where can calluses and corns develop?

Calluses and corns can develop in both thin and thick sin.

How do carotene, blood flow, oxygen content, and collagen affect skin color?

Carotene is a yellow pigment found in plants, such as carrots and corn. Humans normally ingest carotene and use it as a source of vitamin A. Carotene is lipid-soluble and, when large amounts of carotene are consumed, the excess accumulates in the stratum corneum and in adipocytes of the dermis and subcutaneous tissue, causing the skin to develop a yellowish tint. The yellowish tint slowly disappears once carotene intake is reduced. The location of pigments and other substances in the skin affects the color produced. For example, light reflected off dark pigment in the dermis or subcutaneous tissue can be scattered by collagen fibers of the dermis to produce a blue color. The same effect produces the blue color of the sky as light is reflected from dust particles in the air. The deeper within the dermis or subcutaneous tissue any dark pigment is located, the bluer the pigment appears because of the light-scattering effect of the overlying tissue. This effect causes the blue color of tattoos, bruises, and some superficial blood vessels.

Melanocytes

Cell found mainly in the stratum basal; produces the brown or black pigment melanin.

Whats the difference between soft keratin and hard keratin?

Cells containing hard keratin are more durable than cells with soft keratin, and they are not shed.

What conditions can cause an increase in melanin production?

Certain conditions may cause increases in melanin production and therefore changes in pigmentation in areas of the body. During pregnancy, certain hormones, such as estrogen and melanocyte-stimulating hormone, cause the mother's body to increase melanin production, which causes darkening of the nipples, areolae, and genitalia. The cheekbones, forehead, and chest also may darken, resulting in the "mask of pregnancy." In addition, a dark line of pigmentation may appear on the midline of the abdomen.

What does cerumen do?

Cerumen and hairs in the ear canal protect the tympanic membrane by preventing dirt and small insects from moving too deeply into the ear canal. However, an accumulation of cerumen can block the ear canal and make hearing more difficult.

What is cerumen composed of?

Cerumen, or earwax, is composed of the combined secretions of ceruminous glands and sebaceous glands.

Psoriasis

Chronic skin disease characterized by thicker-than-normal epidermal layer (stratum corneum) that sloughs to produce large, silvery scales; bleeding may occur if the scales are scraped away.

Stratum lucidum

Clear layer of the epidermis found in thick skin between the stratum granulosum and the stratum corneum.

What are the major types of protein found in the extracellular matrix of the dermis?

Collagen is the main type of protein fiber of the extracellular matrix, but elastic and reticular fibers are also present.

Birthmarks

Congenital (present at birth) disorders of the dermal capillaries.

What does the contraction of arrector pili muscles cause?

Contraction of the arrector pili muscles causes hair to stand on end, but this does not significantly reduce heat loss in humans because so little hair covers the body. However, the hair on the head is an effective insulator. We consider general temperature regulation further in chapter 25.

Some drugs are administered by applying them to the skin (e.g., a nicotine skin patch to help a person stop smoking). The drug diffuses through the epidermis to blood vessels in the dermis. What kind of substances can pass easily through the skin by diffusion? What kinds of substances have difficult diffusing through the skin?

Correct Answer: In the description of the epidermis, the superficial layer of the skin, we learned that the keratinized cells are coated with lipids to prevent fluid loss. Recall from chapter 3 that substances that are lipid-soluble easily diffuse through lipid layers but water-soluble substances do not. By applying the same principles of diffusion across cell membranes to diffusion across the skin, we can predict that lipid-soluble substances diffuse easily but water-soluble substances do not.

Does cutting, shaving, or plucking hair alter the growth rate?

Cutting, shaving, or plucking hair does not alter the growth rate or character of the hair, but hair can feel coarse and bristly shortly after shaving because the short hairs are less flexible.

How long does it take deep partial-thickness and full-thickness to heal?

Deep partial-thickness and full-thickness burns take a long time to heal, and they tend to form scar tissue with disfiguring and debilitating wound contracture.

What happens deeper in the hair follicle?

Deeper in the hair follicle, the number of cells decreases until, at the hair bulb, only the stratum basale is present.

Dermis

Dense irregular connective tissue that forms the deep layer of the skin.

Decubitus ulcers (bedsores, pressure sores)

Develop in people who are bedridden or confined to a wheelchair; compression of tissue and reduced circulation result in destruction of the skin and subcutaneous tissue, which later become infected by bacteria, forming ulcers.

Vitiligo

Development of patches of white skin where melanocytes are destroyed, apparently by an autoimmune response

What diseases cause increased pigmentation?

Diseases that cause increased secretion of adrenocorticotropic hormone and melanocyte-stimulating hormone, such as Addison disease, also cause increased pigmentation.

What can dopaquinone be converted to?

Dopaquinone can be converted to a variety of related molecules, most of which are brown to black pigments but some of which are yellowish or reddish.

What happens during keratinization?

During keratinization, the cells eventually die and produce an outer layer of dead, hard cells that resists abrasion and forms a permeability barrier.

What happens during preparation for microscopic observation?

During preparation for microscopic observation, the cells usually shrink from one another, except where they are attached by desmosomes, causing the cells to appear spiny-hence the name stratum spinousum.

Which glands of the skin are responsible for cooling the body? Where are they located? Which glands are involved with producing body odor? Where are they located?

Eccrine sweat glands are the most common type of sweat gland. They are simple, coiled, tubular glands that open directly onto the surface of the skin through sweat pores. Eccrine sweat glands can be divided into two parts : (1) the deep, coiled portion, which is located mostly in the dermis; and (2) the duct, which passes to the skin surface. The coiled part of the gland produces an isotonic fluid that is mostly water but also contains some salts (mainly sodium chloride) and small amounts of ammonia, urea, uric acid, and lactic acid. as this fluid moves through the duct, sodium chloride moves by active transport from the duct back into the body, thereby conserving salts. The resulting hyposmotic fluid that leaves the duct is called sweat. When the body temperature starts to rise above normal, the sweat glands produce sweat, which evaporates and cools the body. Sweat also can be released in the palms, soles, and axillae as are result of emotional stress. Eccrine sweat glands are distributed over the majority of the areas of the body but are most numerous in the palms of the hands and soles of the feet. Eccrine sweat glands are not found on the margin of the lips, the labia minor, and the tips of the penis and clitoris. Appocrine sweat glands are simple, coiled, tubular glands that usually open into hair follicles superficial to the opening of the sebaceous glands. Apocrine sweat glands are found in the axillae and genitalia (scrotum and labia major) and around the anus. Unlike eccrine sweat glands, apocrine sweat glands do not help regulate temperature in humans. Apocrine sweat glands become active at puberty as a result of sex hormones. Their secretions contain organic substances but are quickly metabolized by bacteria to cause what is commonly known as body odor. Many mammals use scent as a means of communication, and physiologists have suggested that the activity of apocrine sweat glands may signal sexual maturity.

What happens to elderly people that do not take precautions to regulate their temperature?

Elderly individuals who do not take proper precautions may experience heat exhaustion, which can even lead to death.

Why is the quantity of waste products eliminate in sweat insignificant?

Even when large amounts of sweat are lost, the quantity of waste products eliminated in the sweat is insignificant because the urinary system excretes most of the body's waste products.

How are cells from the stratum corneum shed from the skin?

Eventually, the desmosomes break apart, and the cells are shed from the surface of the skin.

Does everyone have friction ridge patterns?

Everyone has unique friction ridge patterns, even identical twins.

How does drandruff occur?

Excessive shedding of the stratum corneum of the scalp results in dandruff.

What substance are excreted in sweat? Is the skin an important site of excretion?

Excretion is the removal of waste products from the body. In addition to water and salts, sweat contains a small amount of waste products, including urea, uric acid, ammonia. However, even when large amounts of sweat are lost, the quantity of waste products eliminated in the sweat is insignificant because the urinary system excretes most of the body's waste products.

What are facial burns associated with?

Facial burns are often associated with damage to the respiratory tract.

What do first-degree burns involve?

First-degree burns involve only the epidermis and may result in redness, pain, and slight edema (swelling).

How can the surface area that is burned in adults be estimated?

For an adult, the surface area that is burned can be conveniently estimated by "the rule of nines," which divides the body into areas that are approximately 9%, or multiples of 9%, of the body surface area.

What is an example of the location of pigments effecting the color produced?

For example, light reflected off dark pigment in the dermis or subcutaneous tissue can be scattered by collagen fibers of the dermis to produce a blue color. The deeper within the dermis or subcutaneous tissue any dark pigment is located, the bluer the pigment appears because of the light-scattering effect of the overlying tissue. This effect causes the blue color of tattoos, bruises, and some superficial blood vessels.

What is an example of glands on the skin?

For example, mammary glands are a type of skin gland that are normally only functional in lactating woman.

Give an example of how stretch marks are formed?

For example, stretch marks commonly form on the abdomen and breasts of a woman during pregnancy or on the skin of athletes who have quickly increased muscle size by intense weight training.

Whats an example of receptors detecting pain, heat, cold, and pressure.

For example, the epidermis and dermal papillae are well supplied with touch receptors. The dermis and deeper tissues contain pain, heat, cold, touch, and pressure receptors. Hair follicles (but not the hair ) are well enervated, and sensory receptors surrounding the base of hair follicles can detect hair movement.

What is an example of skin being thick and thin?

For example, the skin of the back is thin skin, whereas that of the palm of the hand is thick skin; however, because the dermis of the skin of the back is thicker, the total skin thickness of the back is greater than that of the palm.

What is an example of what thin skin contains?

For example, the stratum granulosum frequently consists of only one or two layers of cells, as opposed to the three to five layers in thick skin.

How is tanning produce?

For those individuals who are able to produce melanin, exposure to ultraviolet light darkens the melanin already present in the skin and stimulates melanin production, resulting in tanning.

How the surface area for measuring burns different in children versus adults?

For younger patients, surface area relationships are different. For example, in an infant, the head and neck are 21% of BSA, where as in an adult they are 9%. For burn victims younger than age 15, a table specifically developed for them should be consulted.

What are some alternatives to lack of vitamin D being produced?

Fortunately, vitamin D can also be ingested and absorbed in the small intestine. Natural sources of vitamin D are liver (especially fish liver), egg yolks, and dairy products (e.g., butter, cheese, and milk). In addition, the diet can be supplemented with vitamin D in fortified milk or vitamin pills.

What are fourth-degree burns?

Fourth-degree burns are extremely severe burns that affect tissues deeper than the subcutaneous tissue, often damaging tendons, fascia, muscle, and bone.

What are the five strata from deepest to most superficial?

From the deeper to the most superficial, the five strata are (1) Stratum basale (2) Stratum spinosum (3) Stratum granulosum (4) Stratum lucidum (5) Stratum corneum

While trying to fix some loose boards on his deck, Bob hit his left thumb with his hammer. The hammer struck his thumbnail distal to the lunula and proximal to the hyponychium. After a short period, a dark area appeared in the area on of the nail bed. The injury was very painful until a physician drilled a small hole through Bob's nail, releasing bloody fluid. After nearly 2 months, the dark area moved to the free edge of the nail. Explain why a dark area developed in the nail. What caused Bob's pain, and why did drilling a hole in his nail relieve it? Why did the dark area move distally over time?

From the description of the injury, we know that the hammer struck Bob's nail bed. It is apparent that the hit was hard enough to rupture small blood vessels deep to the nail matrix. Blood accumulated between the nail and the nail bed, causing the dark area. In chapter 4 we learned that inflammation is the response that occurs when tissues are damaged and a normal inflammatory event is edema, or swelling at the injury site. The accumulation of blood and edema increased the pressure deep to the nail body, which stimulated pain receptors. When a hole was drilled through the nail, the accumulated bloody fluid drained, reducing the pressure and, consequently, the pain. Since the nail matrix, which is proximal to the injury site, was not injured, the nail continued to grow over the next 2 months, until the injured area was pushed distally to the free edge of the nail.

What are full-thickness burns?

Full-thickness burns are also called third-degree burns.

Ringworm

Functional infection that produces patchy scaling and inflammatory response in the skin.

What causes pattern baldness?

Genetic factors and the hormone testosterone are involved in causing pattern baldness.

What are genetic factors responsible for?

Genetic factors are primarily responsible for the variations in skin color among different races and among people of the same race.

Genital herpes

Genital lesions; caused by herpes simplex II virus; transmitted by sexual contact.

Sebaceous glands

Gland of the skin, usually associated with a hair follicle, that produces sebum.

Apocrine sweat glands

Gland whose cells contribute cytoplasm to its secretion. Sweat glands that produce organic secretions traditionally are called apocrine. These sweat glands, however, are actually merocrine glands.

Melanin

Group of related molecules responsible for skin, hair, and eye color. Most melanins are brown to black pigments; some are yellowish or reddish.

What is hair color the result of?

Hair color is the result of melanin production by melanocytes and the distribution of melanin to the cells of the hair. Similar to how melanocytes of the epidermis produce melanin and pass it to the keratinocytes of the skin, melanocytes within the hair bulb matrix produce melanin and pass it to keratinocytes in the hair cortex and medulla.

What determines the different shades of hair color?

Hair color is the result of melanin production by melanocytes and the distribution of melanin to the cells of the hair. Similar to how melanocytes of the epidermis produce melanin and pass it to the keratinocytes of the skin, melanocytes within the hair bulb matrix produce melanin and pass it to keratinocytes in the hair cortex and medulla. As with the skin, varying amounts and types of melanin cause different shades of hair color. Blonde hair has little black-brown melanin, whereas jet black hair has the most. Intermediate amounts of melanin account for different shades of brown. Red hair is caused by varying amounts of a red type of melanin. Hair sometimes contains both black-brown and red melanin. Hair color is controlled by several genes, and dark hair color is not necessarily dominant over light. With age, the amount of melanin in hair can decrease, causing hair color to fade or become white (i.e., no melanin). Gray hair is usually a mixture of unfaded, faded, and white hairs.

What happens in "pattern baldness?"

Hair follicles shrink and revert to producing vellus hair, which is very short, transparent, and for pratical purposes invisible. Eventually, hair production in these smaller follicles may completely cease.

What are the cycles that hair are produced in?

Hair is produced in cycles that involve a growth stage and a resting stage.

In what part of hair does growth take place? What are the stages of hair growth? Do all hairs grow at the same rate?

Hair is produced in cycles that involve a growth stage and a resting stage. During the growth stage, a hair increases in length as new matrix cells are produced, differentiate, become keratinized, and die. The hair grows longer as cells are added at the base of the hair root. Eventually, hair growth stops; the hair follicle shortens and holds the hair in place. A resting period follows, after which a new cycle begins. With this new cycle, a new hair forms to replace the old hair, which falls out of the hair follicle. Thus, losing a hair normally means that the hair is being replaced. The length of each stage depends on the hair-eyelashes grow for approximately 30 days and rest for 105 days, whereas scalp hairs grow for 3 year and rest for 1-2 years. At any give time, an estimated 90% of the scalp hairs are in the growing stage. It is normal for a person to lose approximately 100 scalp hairs per day.

How can hair loss be more extensive?

Hair loss can be more extensive than the normal 100 hairs per day. In some cases, extensive hair loss may occur, but hair growth may return, such as occurs in patients receiving certain chemotherapies.

What type of melanin does hair sometimes contain?

Hair sometimes contains both black-brown and red melanin.

When and where are lanugo, vellus, and terminal hairs found in the skin?

Hair structure and coloration change as a person ages. By the fifth or sixth month of fetal development, delicate, unpigmented hair called lanugo has developed and covered in the fetus. Near the time of birth, long, coarse, and pigmented hairs called terminal hairs replace the lanugo of the scalps eyelids, and eyebrows. Vellus hairs, which are short, fine, and usually unpigmented, replace the lanugo on the rest of the body. At puberty, terminal hair, especially in the pubic an axillary regions, replaces much of the vellus hair. The hair of the chest, legs, and arms is approximately 90% terminal hair in males and approximately 35% in females. In males, terminal hairs replace the vellus hairs of the face to form the beard. These changes in hair type at puberty are universal and have biological significance. The beard, pubic, and axillary hair are visible signs of sexual maturity. In addition, pubic and axillary hair may function as wicks for dispersing odors produced by secretions from specialized glands in the pubic and axillary region acting as olfactory signals to others. It also has been suggested that pubic hair protects against abrasion during intercourse and axillary hair reduces friction when the arms move against the body.

Explain the development of hair as babies develop?

Hair structure and coloration change as a person ages. By the fifth or sixth month of fetal development, delicate, unpigmented hair called lanugo has developed and covered the fetus.

How long does it take for second-degree burns to heal?

Healing takes approximately 2 weeks, and no scarring results. However, if the burn goes deep into the dermis, the wound appears red, tan, or white; may take several months to heal; and might scar.

What is carotene used for?

Humans normally ingest carotene and use it as a source of vitamin A.

How are stretch marks formed?

If the skin is overstretched, the dermis may rupture and leave lines that are visible through the epidermis. These lines of scar tissue, called stretch marks, can develop in the skin of individuals who have experienced rapid growth.

What happens in a split skin graft?

In a split skin graft, the epidermis and part of the dermis are removed from another part of the body and placed over the burn. Interstitial fluid from the burned area nourishes the graft until its dermis becomes vascularized. At the graft donation site, part of the dermis is still present.

What does sweat contain?

In addition to water and salts, sweat contains a small amount of waste products, including urea, uric acid, and ammonia.

What regenerates second-degree burns?

In all second-degree burns, the epidermis regenerates from epithelial tissue in hair follicles and sweat glands, as well as from the edges of the wound.

Where is hair found?

In humans, hair is found everywhere on the skin except the palms, the soles, the lips, the nipples, parts of the external genitalia, and the distal segments of the fingers and toes.

What does terminal hair replace in males?

In males, terminal hairs replace the vellus hairs of the face to form the beard.

How is a callus formed?

In skin subjected to friction or pressure, an area called a callus often forms when the stratum corneum of the epidermis increases in thickness.

What happens to the stratum granulosum, the nucleus and other organelles in the most superficial layer?

In the most superficial layers of the stratum granulosum, the nucleus and other organelles degenerate, and the keratinocyte dies. Unlike the other organelles and the nucleus, however, the keratin fibers and keratohyalin granules within the cytoplasm do not degenerate.

Frostbite is the most common type of freezing injury. When skin temperature drops below 0 degrees celsius (32 degrees Ferenheit), the skin freezes and ice crystal formation damage tissues. a. Using figure 5.10, describe the mechanism that cause Billy's ears and nose to become pale. how is this mechanism beneficial when the ambient temperature is decreasing? b. Explain what happened when Billy's ears and nose periodically turned red. How is this beneficial when the ambient temperature is very cold? c. What is the significance of Billy's ears and nose turning and staying white? d. Why is a person with frostbite likely to develop an infection of the affected part of the body?

In this chapter we learned that body temperature is affected by blood flow in the skin. When body temperature decreases, blood flow through the skin also decreases to reduce heat loss. Billy's ears and nose turned pale because of decreased blood flow. Constriction of blood vessels in Billy's skin reduced heat loss and helped maintain his body temperature. Recall that the redness of skin is due to increased blood flow through the skin, so Billy's ears and nose turned red because of increased blood flow. As skin temperature decreases and blood vessels constrict, tissue can be damaged by the lack of blood flow and ice crystal formation. Cold-induced vasodilation periodically increases blood flow and prevents or slows the rate of ice crystal formation. This strategy for maintaining tissue homeostasis is beneficial as long as body temperature can be maintained. Also, we learned that blood flow determines the distribution of heat to different regions of the body. The red appearance of the nose and ears indicates increased blood flow in these areas, and we can assume that this leads to warming of this tissue that is probably very cold due to the weather. The white color indicates the complete lack of blood flow through the skin of his ears and nose. The tissue will most likely be damaged due to the absence of blood flow in these areas. Remember that one of the major functions of the skin is to prevent microorganisms from entering the body. If frostbite destroys skin cells, this function can be compromised, resulting in infection.

Eczema and dermatitis

Inflammatory conditions of the skin caused by allergy, infection, poor circulation, or exposure to chemical or environmental factors.

What are injections used for?

Injections are used to introduce certain substances, such as medication and vaccines, into the body by puncturing the skin.

What is the matrix?

Inside the hair bulb is a mass of undifferentiated epithelial cells called the matrix.

What does intermediate amounts of melanin account for?

Intermediate amounts of melanin account for different shades of brown.

Hair follicle

Invagination of the epidermis into the dermis; contains the root of the hair and receives the ducts of sebaceous and apocrine glands.

What does the stratum lucidum consist of?

It consist of several layers of dead keratinocytes with indistinct boundaries. Keratin fibers are present, but the keratohyalin, which was evident as granules in the stratum granulosum, has dispersed around the keratin fibers, and the cells appear somewhat transparent.

What does the integumentary system do?

It forms the boundary between the body and the external environment, thereby separating us from the external environment while allowing us to interact with it.

What does the reticular layer form?

It is continuous with the subcutaneous tissue and forms a mat of irregularly arranged fibers that are resistant to stretching in many directions.

Why is it important to understand the cleavage line?

It is important for health professionals to understand cleavage line directions because an incision made parallel to the cleavage lines is less likely to gap than an incision made across them. The development of infections and the formation of scar tissue are reduced in wounds where the edges are closer together.

Is the number of melanocytes in the skin the same for all humans?

It is interesting to note that the number of melanocytes in the skin is relatively the same for all humans, regardless of race.

What separates the epidermis from the underlying dermis?

It is separate from the underlying dermis by a basement membrane.

What gives the epidermis its ability to resist abrasion and reduce water loss?

It is the durability of the keratinocytes that give the epidermis its ability to resist abrasion and reduce water loss.

How long does it take for the cell to reach the epidermal surface and slough off?

It takes 40-56 days for the cell to reach the epidermal surface and slough off.

What is the primary role of vitamin D?

Its primary role is to stimulate the uptake of calcium and phosphate from the small intestine. Adequate levels of these minerals are necessary for normal bone metabolism and calcium is required for normal nerve and muscle function.

What is keratin?

Keratin is a mixture of keratin fibers and keratohyalin.

How often do keratinocyte stem cells undergo mitotic divisions?

Keratinocyte stem cells of the stratum basale undergo mitotic divisions approximately every 19 days.

What strengthens keratinocytes?

Keratinocytes are strengthened internally by keratin fibers (intermediate filaments) that insert into the desmosomes.

What do keratinocytes phagocytize?

Keratinocytes phagocytize the tips of the melanocyte cell processes, thereby acquiring melanosomes. Although all keratinocytes can contain melanin, the only cells that produce it are melanocytes.

What are Langerhans cells?

Langerhans cells are part of the immune system.

Where is melanin found?

Large amounts of melanin are found in certain regions of the skin, such as freckles, moles, the nipples, the areola of the breasts, the axillae, and the genitalia. Others ares of the body, such as lips, palms of the hands, and soles of the feet, contain less melanin.

Stratum granulosum

Layer of cells in the epidermis filled with granules of keratohyalin.

Stratum spinosum

Layer of many-sided cells in the epidermis with intercellular connections (desmosomes) that give the cells a spiny appearance.

Can you feel fourth-degree burns?

Like third-degree burns, fourth-degree burns are painless due to the destruction of sensory receptors.

What is released from the lamellar bodies and what is it responsible for?

Lipids are released from lamellar bodies surrounding the skin cells. The lipids are responsible for many of the skin's permeability.

Explain why placing an ice pack on an area of skin results in the area appearing red.

Making the surface of the skin really cold makes blood vessels constrict which causes the skin to turn red. Making the skin surface really cold makes the skin break into hives.

What is maximum hair length determined by?

Maximum hair length is determined by the rate of hair growth and the length of the growing phase. For example scalp hair become very long but eyelashes stay short.

What does melanin provide?

Melanin also provides protection against ultraviolet light from the sun.

What is melanin produced by?

Melanin is produced by melanocytes, irregularly shaped cells with many long processes that extend between the keratinocytes of the stratum basal and the stratum spinous.

What is melanin production determined by?

Melanin production is determined by genetic factors, exposure to light, and hormones.

PROCESS FIGURE 5.4 Melanin Transfer to Keratinocytes.

Melanocytes make melanin, which is packaged into melanosomes and transferred to many keratinocytes. Melanin protects a cell's DNA from UV damage.

What do melanocytes produce?

Melanocytes produce and package melanin into vesicles called melanosomes, which move into cell processes of the melanocytes.

What are melanocytes?

Melanocytes, produce the pigment melanin, which contributes to skin color.

Melanoma

Melanoma is the least common, but most deadly, type of skin cancer, accounting for over 77% of the skin cancer deaths in the United States. Because they arise from melanocytes, most melanomas are black or brown, but occasionally a melanoma stops producing melanin and appears skin-colored, pink, red, or purple. About 40% of melanomas develop in preexisting moles. Treatment of melanomas when they are confined to the epidermis is almost always successful. However, if a melanoma invades the dermis and metastasizes (spreads) to other parts of the body, it is difficult to treat and can be deadly.

What are Merkel cells?

Merkel cells are specialized epidermal cells associated with the nerve endings responsible for detecting light touch and superficial pressure.

Ceruminous glands

Modified sebaceous glands in the external acoustic meatus that produce cerumen (earwax).

Explain differences in adipose tissue between babies and adults.

Most babies have a chubby appearance because they have proportionately more adipose tissue than adults.

What kinds of cells make up the epidermis?

Most cells of the epidermis are called keratinocytes because they produce a protein mixture called keratin, which makes the cells more durable. Other cells of the epidermis include melanocytes, Langerhans cells, and Merkel cells.

What is the root and shaft composed of?

Most of the root and the shaft are composed of columns of dead, keratinized epithelial cells arranged in three concentric layers. (1) the medulla (2) the cortex, and (3) the cuticle.

Describe the three layers of a hair seen in cross section.

Most of the root and the shaft are composed of columns of dead, keratinized epithelial cells arranged in three concentric layers: (1) the medulla, (2) the cortex, and (3) the cuticle. The medulla is the central axis of the hair, and it consists of two or three layers of cells contains soft keratin. The cortex surrounds the medulla and forms the bulk of the hair. The cells of the cortex contain hard keratin. The cortex is covered by the cuticle, a single layer of cells also containing hard keratin. The edges of the cuticle cells overlap like shingles on a roof.

Where do most sebaceous glands release their secretions?

Most sebaceous glands release their secretions into the upper part of the hair follicles through a duct.

What does movement of hair follicles produce?

Movement of the hair follicles produces raised areas called "goose bumps." This is a common response to cold temperatures as well as strong emotional responses.

Where are nails located?

Nails are located on the distal ends of the digits (fingers and toes).

What is the growing rate of nails?

Nails grow at an average rate of 0.5-1.2 mm per day, and fingernails grow more rapidly than toenails. Unlike hair, they grow continuously through out life and do not have a resting phase.

Explain the development of hair as a baby is born.

Near the time of birth, long, coarse, and pigmented hairs called terminal hairs replace the lanugo of the scalp, eyelids, and eyebrows.

What is the angle of hair follicles and the hair inside the papillary layer?

Normally, the hair follicle and the hair inside it are at an oblique angle to the surface of the skin.

On the basis of depth how are burns classified?

On the basis of depth, burns are classified as either partial-thickness or full-thickness burns.

What are the layers of cells in the epidermis divided into?

On the basis of these stages, the many layers of cells in the epidermis are divided into regions, or strata (sing. stratum; figures 5.2b and 5.3).

What happens in mitosis for keratinocyte stem cells?

One daughter cell remains a stem cell in the stratum basale and divides again, but the other daughter cell is pushed toward the surface and becomes keratinized.

What is one ironic side effect of Retin-A?

One ironic side effect of Retin-A use is increased sensitivity to the sun's ultraviolet rays. Doctors prescribing this cream caution their patients to always use a sunblock when they are going to be outdoors.

Shingles

Painful skin lesions; caused by the chickenpox virus after childhood infection; can recur when the dormant virus is activated by trauma, stress, or another illness.

How are partial-thickness burns subdivided?

Partial-thickness burns are subdivided into first- and second- degree burns.

FIGURE 5.12 Burns

Partial-thickness burns are subdivided into first-degree burns (damage to only the epidermis) and second-degree burns (damage to the epidermis and part of the dermis). Full-thickness, or third-degree, burns destroy the epidermis, the dermis, and subcutaneous tissue. Fourth-degree burns (not shown in the figure) destroy tissue deeper than the subcutaneous tissue.

Explain how humans produce vitamin D.

People can produce all the vitamin D they require by this process if enough ultraviolet light is available; however, because people live indoors and wear clothing, their exposure to ultraviolet light may not be adequate for the manufacture of sufficient vitamin D. This is especially likely for people living in cold climates because they remain indoors or are covered by warm clothing when outdoors.

You just learned that acne-causing bacteria tend to live in areas of the skin with many sebaceous glands. However, in section 5.4, it states that sebum protects against certain bacteria. a. Based on what you've learned about bacteria in the Microbes in Your Body 1. and 3.1, why do you think P. acnes are able to survive the antibacterial effects of sebum? b. Why do you think certain acne medications are so effective simply by inhibiting sebum production?

Previously, we learned that bacteria are ubiquitous and are able to survive in environments thought to be uninhabitable by any organism. We also learned that each bacterial species is unique. It is probable that P. acnes are resistant to the anti-bacterial properties of sebum. In fact, you learned that P. acnes require sebum to survive. The bacteria consume components of sebum. Since P. acnes are dependent on sebum for their survival, reducing the total amount of sebum produced starves P. acnes of essential nutrients. The skin without enough sebum to feed P. acnes becomes a very unwelcoming environment for these pesky bacteria.

Keratinization

Production of keratin and changes in the chemical and structural character of epithelial cells as they move to the skin surface.

1. Provide an example for each function of the integumentary system.

Protection. Though exposed to the external environment, the skin's structure reduces the negative and harmful effects of ultraviolet light. Acting as a barrier, the skin also keeps microorganisms from entering the body and prevents dehydration by reducing water loss. Sensation. The integumentary system has sensory receptors that can detect heat, cold, touch, pressure, and pain. Temperature regulation. The skin plays a major role in regulating body temperature through the modulation of blood flow through the skin and the activity of sweat glands. Vitamin D production. When exposed to ultraviolet light, the skin produces a molecule that can be transformed into the hormonal form of vitamin D, an important regulator of calcium homeostasis. Excretion. Small amounts of waste products are excreted through the skin and glands.

What determines the racial variations in skin color?

Racial variations in the skin color are determine by several major factors: -types of melanin produced -amount of melanin produced -size of melanosomes (melanin-filled vesicles in cells) -number of melanosomes -distribution of melanosomes.

What does connective tissue consist of?

Recall from chapter 4 that connective tissue consists of cells distributed widely in an extensive extracellular matrix, which includes protein fibers.

What do receptors in the skin detect?

Receptors in the skin can detect pain, heat, cold, and pressure.

What kinds of sensory receptors are in the skin, and why are they important?

Receptors in the skin can detect pain, heat, cold, and pressure. For example, the epidermis and dermal papillae are well supplied with touch receptors. The dermis and deeper tissues contain pain, heat, cold, touch, and pressure receptors. Hair follicles (but not the hair ) are well innervated, and sensory receptors surrounding the base of hair follicles can detect hair movement. Sensory receptors are discussed in more detail in chapter 14.

What vitamin treats wrinkles in skin?

Retin-A is a vitamin A derivative that appears to be effective in treating fine wrinkles on the face, such as those caused by long-term exposure to the sun; it is not effective in treating deep lines.

What do sebacoeous glands secrete? What is the function of the secretion?

Sebaceous glands, located in the dermis, are simple or compound alveolar glands that produce sebum, an oily, white substance rich in lipids because sebum is released by the lysis and death of secretory cells, sebaceous glands are classified as holcorine glands. Most sebaceous glands release their secretions into the upper part of the hair follicles through duct. The secretion of sebum onto the hair and surrounding skin prevents drying and protects against some bacteria. A few sebaceous glands located in the lips, the eyelids (meibomian glands), and the genitalia are not associated with hairs but open directly onto the skin surface.

What are sebaceous glands?

Sebaceous glands, located in the dermis, are simple or compound alveolar glands that produce sebum, an oily, white substance rich in lipids.

What do second-degree burns damage?

Second-degree burns damage the epidermis and dermis. Minimal dermal damage cause redness, pain, edema, and blisters.

Define the different categories of burns. How is repair accomplished after each type?

Second-degree burns damage the epidermis and dermis. Minimal dermal damage causes redness, pain, edema, and blisters. Healing takes approximately 2 weeks, and no scarring results. However, if the burn goes deep into the dermis, the wound appears red, tan, or white; may take several months to heal; and might scar. In all second-degree burns, the epidermis regenerates from epithelial tissue in hair follicles and sweat glands, as well as from the edges of the wound. Full-thickness burns are also called third-degree burns. The epidermis and dermis are completely destroyed, and tissue just below the skin may be involved. Third-degree burns are often surrounded by first and second-degree burns. Although the areas that have first- and second-degree burns are painful, the region of third-degree burn is usually painless because the sensory receptors have been destroyed. Third-degree burns appear white, tan, brown, bald, or deep cherry-red. Skin can regenerate only from the edges, and skin grafts are often necessary. Fourth-degree burns are extremely severe burns that affect tissues deeper than the subcutaneous tissue, often damaging tendons, fascia, muscle, and bone. Like third-degree burns, fourth-degree burns are painless due to the destruction of sensory receptors. Because of the severity of tissue damage, fourth-degree burns often require amputation or removal of damaged tissue. Death may occur due to the increased likelihood of infection. Deep partial-thickness and full-thickness burns take a long time to heal, and they tend to form scar tissue with disfiguring and debilitating wound contracture. To prevent these complications and speed healing, skin grafts are performed. In a split skin graft, the epidermis and part of the dermis are removed from another part of the body and placed over the burn. Interstitial fluid from the burned area nourishes the graft until its dermis becomes vascularized. At the graft donation site, part of the dermis is still-present. The deep parts of hair follicles and sweat gland ducts remain in this dermis, where they serve as a source of epithelial cells that form a new epidermis. This is the same process of epidermis formation that occurs following superficial second-degree burns.

Frostbite

See Case Study 5.1

Skin cancer

See Clinical Impact 5.1

Acne

See Microbes in Your Body 5.1

Alopecia areata

See section 5.4

Vellus hairs

Short, fine, usually unpigmented hair that covers the body except for the scalp, eyebrows, and eyelids. Much of the vellus is replaced at puberty by terminal hairs.

How does the skin regenerate for third degree burns?

Skin can regenerate only from the edges, and skin grafts are often necessary.

How else can skin color change?

Skin color can also show variation due to changes in blood flow. These changes in skin color are not as long lasting and often dissipate in a few minutes or hours.

What is the skin more prone to as the body ages?

Skin infections are more likely, and skin repair occurs more slowly.

Rubeola (measles)

Skin lesion; caused by a virus contracted through the respiratory tract; may develop into pneumonia or infect the brain, causing damage.

Cold sores (fever blisters)

Skin lesion; caused by herpes simplex I virus; transmitted by oral or respiratory routes; lesions recur

Chickenpox

Skin lesions; usually mild viral disease contracted through the respiratory tract

Rubella (German measles)

Skin lesions; usually mild viral disease contracted through the respiratory tract; may be dangerous if contracted during pregnancy because the virus can cross the placenta and damage the fetus.

What happens to skin that is exposed to sunlight?

Skin that is exposed to sunlight appears to age more rapidly than non exposed skin. This effect is observed on areas of the body that receive sun exposure, such as the face and hands. However, the effects of chronic sun exposure on the skin are different from the effects of normal aging. In skin expose to sunlight, normal elastic fibers are replaced by an interwoven mat of thick, elastic-like material, the number of collagen fibers decreases, and the ability of keratinocytes to divide is impaired.

What effect does exposure to sunlight have on skin?

Skin that is exposed to sunlight appears to age more rapidly than non exposed skin. this effect is observed on areas of the body that receive sun exposure, such as the face and hands. However, the effects of chronic sun exposure on the skin are different from the effects of normal aging. In skin exposed to sunlight, normal elastic fibers are replaced by an interwoven mat of thick, elastic-like material, the number of collagen fibers decreases, and the ability of keratinocytes it divide is impaired.

Impetigo

Smal blisters containing pus; easily rupture to form a thick yellowish rust; usually affects children

How does the integumentary system provide excretion?

Small amounts of waste products are excreted through the skin and glands.

arrector pili

Smooth muscle attached to the hair follicle and dermis that raises the hair when it contracts.

What substances readily pass through the skin?

Some lipid-soluble substances readily pass through the epidermis. Lipid-soluble medications can be administered by applying them to the skin, after which the medication slowly diffuses through the skin into the blood. For example, nicotine patches are applied to help reduce withdrawal symptoms in people attempting to quit smoking.

Sqaumous cell carncinoma

Sqaumoous cell carcinoma is the second most common type of skin cancer. Squamous cell carcinoma affects cells in the stratum spinousum and can appear as a wartlike growth; a persistent, scaly red patch; an open sore; or an elevated growth with a central depression. These lesions may bleed. Removal or destruction of the tumor cures most cases.

Stratum spinosum

Structure: A total of 8-10 layers of many-sided cells Function: Produces keratin fibers; lamellar bodies from inside keratinocytes.

Dermis

Structure: Deep part of skin; connective tissue composed of two layers Function: Is responsible for the structural strength and flexibility of the skin; the epidermis exchanges gases, nutrients, and waste products with blood vessels in the dermis.

Stratum basale

Structure: Deepest stratum of the epidermis; single layer of cuboidal or columnar cells; basement membrane of the epidermis attaches to the dermis. Function: Produces cells of the most superficial strata; melanocytes produce and contribute melanin, which protects against ultraviolet light.

Reticular layer

Structure: Mat of collagen and elastic fibers; dense irregular connective tissue. Function: Is the main fibrous layer of the dermis; strong in many directions; forms cleavage lines

Stratum corneum

Structure: Most superficial stratum of the epidermis; 25 or more layers of dead squamous cells Function: Provides structural strength due to keratin within cells; prevents water loss due to lipids surrounding cells; sloughing off of most superficial cells resists abrasion.

Subcutaneous tissue

Structure: Not part of the skin loose connective tissue with abundant deposits of adipose tissue. Function: Attaches the dermis to underlying structures; adipose tissue provides energy storage, insulation, and padding; blood vessels and nerves from the subcutaneous tissue supply the dermis.

Papillary layer

Structure: Papillae project toward the epidermis; loose connective tissue. Function: Brings blood vessels close to the epidermis; dermal papillae form fingerprints and footprints.

Epidermis

Structure: Superficial part of skin; stratified squamous epithelium; composed of four or five strata. Function: Prevents water loss and the entry of chemicals and microorganisms; protects against abrasion and harmful effects of ultraviolet light; produces vitamin D; gives rise to hair, nails, and glands.

Stratum lucidum

Structure: Three to five layers of dead cells; appears transparent; present in thick skin, absent in most thin skin. Function: Disperses keratohyalin around keratin fibers

Stratum granulosum

Structure: Two to five layers of flattened, diamond-shaped cells Function: Produces keratohyalin granules; lamellar bodies release lipids from cells; cells die.

What is superficial to the stratum basale?

Superficial to the stratum basale is the stratum spinousum.

What else does sweat indicate?

Sweat also can be released in the palms, soles, and axillae as a result of emotional stress.

Erysipelas

Swollen patches in the skin caused by the bacterium Streptoccous pyogenes

What is the hypodermis?

Th subcutaneous tissue, which is not part of the skin, is sometimes called the hypodermis.

Based on this information, around which cellular structures would you expect the melanosomes to congregate?

The Golgi apparatus and endoplasmic reticulum, because they are responsible for making and preparing melanosomes to be sent throughout the cell.

what do the accessory skin structures include?

The accessory skin structures include the hair, glands, and nails.

What is the amount of adipose tissue responsible for?

The amount of adipose tissue in the subcutaneous tissue is also responsible for some of the differences in body shape between individuals of the same sex.

How does the amount of adipose tissue in subcutaneous tissue vary?

The amount of adipose tissue in the subcutaneous tissue varies with age, sex, and diet.

List the functions of the adipose tissue within the subcutaneous tissue.

The amount of adipose tissue in the subcutaneous tissue varies with age, sex, and diet. Most babies have a chubby appearance because they have proportionately more adipose tissue than adults. Women have proportionately more adipose tissue than men, especially over the thighs, buttocks, and breasts, which accounts for some of the differences in body shape between women and men. The amount of adipose tissue in the subcutaneous tissue is also responsible for some of the differences in body shape between individuals of the same sex.

Where does the arrector pili stretch too?

The arrector pili extend from the dermal root sheath of the hair follicle to the papillary layer of the dermis.

What is the average rate of hair growth?

The average rate of hair growth is approximately 0.3 mm per day, although hairs grow at different rates, even in the same approximate location.

What are signs of sexual maturity?

The beard, pubic, and axillary hair are visible signs of sexual maturity.

What are the functions of pubic and axillary hair?

The beard, pubic, and axillary hair are visible signs of sexual maturity. In addition, pubic and axillary hair may function as wicks for dispersing odors produced by secretions from specialized glands in the pubic and axillary regions acting as olfactory signals to others. It also has been suggested that pubic hair protects against abrasion during intercourse and axillary hair reduces friction when arms move against the body.

What do the cells of the cortex contain?

The cells of the cortex contain hard keratin.

What do the cells of the dermis include?

The cells of the dermis include fibroblasts, a few adipocytes, and macrophages.

What are ceruminous glands?

The ceruminous glands are modified eccrine sweat glands located in the ear canal (external auditory canal).

How does alopecia areata derive?

The condition is most likely due to an autoimmune response, where the defense cells of the body destroy normal, healthy cells. Regrowth of hair occurs in many individuals, but some experience permanent hair loss.

What provides structural strength?

The connections formed by the hemidesmosomes and desmosomes provide structural strength to the epidermis.

What is the cortex covered by?

The cortex is covered by the cuticle, a single layer of cells also containing hard keratin. The edges of the cuticle cells overlap like shingles on a roof.

What is the cortex?

The cortex surrounds the medulla and forms the bulk of the hair.

What remains in the dermis after a split skin graft is performed?

The deep parts of hair follicles and sweat gland ducts remain in this dermis, where they serve as a source of epithelia cells that form a new epidermis.

What can be combined to classify the seriousness of a burn?

The depth and percentage of BSA affected can be combined with other criteria to classify the seriousness of a burn.

Where is the dermal papillae? and what does it form?

The dermal papillae under the thick skin of the palms of the hands and soles of the feet lie in parallel, curving ridges. These ridges shape the overlying epidermis into patterns called friction ridges.

What are formed by the dermal papillae in thick skin? What roles do they have?

The dermal papillae under the thick skin of the palms of the hands and soles of the feet lie in parallel, curving ridges. These ridges shape the overlying epidermis into patterns called friction ridges. The impressions left on surfaces by these friction ridges form fingerprints and footprints. The friction ridges improve the grip of the hands and feet. Everyone has unique friction ridge patterns, even identical twins.

What is the dermal root sheath divided into?

The dermal root sheath is the portion of the dermis that surrounds the epithelial root sheath.

What else do the dermis contain?

The dermis also contains nerve endings, hair follicles, smooth muscles, glands, and lymphatic vessels.

What allow nutrient and waste exchange in the dermis?

The dermis contains blood vessels that allow for nutrient and waste exchange to the cells of the dermis and the living cells of the epidermis.

How many layers is the dermis composed of?

The dermis is composed of two tissue layers: the superficial papillary layer and the deeper reticular layer.

Name and compare the two layers of the dermis. Which layer is responsible for most of the structural strength of the skin?

The dermis is composed of two tissue layers: the superficial papillary layer and the deeper reticular layer. The papillary layer derives its name from projections, called dermal papillae, that extend toward the epidermis. The papillary layer derives its name from projections, called dermal papillae, that extend toward the epidermis. The papillary layer also contains blood vessels that supply the overlying epidermis with O2 and nutrients, remove waste products, and aid in regulating body temperature. The reticular layer, which is composed of dense irregular connective tissue, is the main layer of the dermis. It is continuous with the subcutaneous tissue and forms a mat of irregularly arranged fibers that are resistant to stretching in many directions. The elastic collagen fibers are oriented more in some directions than in others and produce cleavage lines, or tension lines, in the skin. It is important for health professionals to understand cleavage line directions because an incision made parallel to the cleavage lines is less likely to gap that an incision made across them. The development of infections and the formation of scar tissue are reduced in wounds where the edges are close together.

What is the dermis?

The dermis is connective tissue.

Where does the dermis of the skin project to?

The dermis of the skin projects into the hair bulb as a hair papilla.

What is the nail groove?

The edges of the nail are held in place by the nail groove.

How are cleavage lines produced?

The elastic and collagen fibers are oriented more in some directions than in others and produce cleavage lines, or tension lines, in the skin.

What are cleavage lines, and how are they related to the healing of a cut?

The elastic and collagen fibers are oriented more in some directions than in others and produce cleavage lines, or tension lines, in the skin. It is important for health professional to understand cleavage line directions because an incision made parallel to the cleavage lines is less likely to gap than an incision made across them. The development of infections and the formation of scar tissue are reduced in wounds where the edges are closer together.

What is the thickness of the epidermis and dermis?

The entire skin, including both the epidermis and the dermis, varies in thickness from 0.5 mm in the eyelids to 5.0 mm on the back and shoulders.

What is the envelope and the keratin responsible for?

The envelope and the keratin are responsible for the structural strength of the stratum corneum.

What damage does full-thickness burns cause?

The epidermis and dermis are completely destroyed, and tissue just below the skin may be involved.

What doesn't the epidermis contain?

The epidermis contains no blood vessels.

What is the epidermis composed of?

The epidermis is composed of several types of cells. Most cells of the epidermis are called keratinocytes because they produce a protein mixture called keratin, which makes the cells more durable.

Describe the structural features resulting from keratinization that make the epidermis structurally strong and resistant to water loss.

The epidermis is composed of several types of cells. Most cells of the epidermis are called keratinocytes because they produce a protein mixture called keratin, which makes the cells more durable. It is the durability of the keratinocytes that gives the epidermis its ability to resist abrasion and reduce water loss. Other cells of the epidermis include melanocytes, Langerhans cells, and Merkel cells. The keratinocytes of the epidermis are constantly lost at its surface but are also constantly replaced by new keratinocyte stem cells undergo mitosis in the deepest layer of the epidermis. As new cells form, they push older cells to the surface, where they slough off. The outermost cells in this stratified arrangement protect the cells underneath, and the deeper, replicating cells replace cells lost from the surface. As keratinocytes move from the deeper epidermal layers of the surface, the cells change shape and chemical composition, through the process called keratinization, where the cells accumulate keratin. During keratinization, the cells eventually die and produce an outer layer of dead, hard cells that resists abrasion and forms a permeability barrier. The study of keratinization is important because many skin diseases result from malfunctions in this process.

What is the epidermis?

The epidermis is stratified squamous epithelium and as such has many of the characteristics describe in chapter 4.

What is the epidermis?

The epidermis is the superficial layer of the skin, consisting of stratified squamous epithelial tissue.

Where is the dermis located?

The epidermis rests on the dermis, a layer of connective tissue

What is the epithelial root sheath divided into?

The epithelial root sheath is divided into external and internal parts.

What determines the skin color?

The factors that determine skin color include (1) pigments in the skin, (2) blood circulating through the skin, and (3) the thickness of the stratum corneum.

What defines a major burn?

The following criteria define a major burn: a third-degree burn over 10% or more of the BSA; a second-degree burn over 25% or more of the BSA; or a second- or third-degree burn of the hands, feet, face, genitals, or anal region.

What do the friction ridges improve?

The friction ridges improve the grip of the hands and feet.

Where is the hair bulb expanded?

The hair bulb is an expanded knob at the base of the hair root.

What is a hair follicle?

The hair follicle is a tubelike invagination of the epidermis that extends into the dermis.

Describe the parts of a hair follicle. How is the epithelial root sheath important in skin repair?

The hair follicle is tubelike invagination of the epidermis that extends into the dermis. A hair develops and grows within each hair follicle. A hair follicle consists of a dermal root sheath and an epithelial root sheath. The dermal root sheath is the portion of the dermis that surrounds the epithelial root sheath. The epithelial root sheath is divided into external and internal parts. At the opening of the follicle, the external epithelial root sheath has all the strata found in thin skin. Deeper in the hair follicle, the number of cells decreases until, at the hair bulb, only the stratum basale is present. This arrangement of epidermal cells has important consequences for skin repair. If the epidermis and the superficial part of the dermis are damaged, the keratinocyte stem cells located in the stratum basale of the undamaged part of the hair follicle can be a source of new epithelium.

How much terminal hair is there in males and females?

The hair of the chest, legs, and arms is approximately 90% terminal hair in males and approximately 35% in females.

What do the impressions left on surfaces by these friction ridges provide?

The impressions left on surfaces by these friction ridges form fingerprints and footprints.

What adds protection in areas that receive more mechanical stress?

The increased number of cell layers provides added protection in the area that experiences more mechanical stress.

How does the integumentary system provide sensation?

The integumentary system has sensory receptors that can detect heat, cold, touch, pressure, and pain.

What does the integumentary system include?

The integumentary system includes the skin and accessory structures, such as hair, nails, and glans.

In what ways does the skin provide protection?

The integumentary system is the body's outer barrier, defending it from harm: 1. The skin protects underlying structures from mechanical damage. Both the dermis and the epidermis play roles in this line of defense, but in different ways. The dermis, particularly the irregular dense connective tissue of the reticular layer, provides structural strength, preventing tearing of the skin. The stratified epithelium of the epidermis protects against abrasion. As the outer cells of the stratum corneum slough off, they are replaced by cells from the stratum basale. Calluses develop in areas subjects heavy friction on pressure. 2. The skin prevents microorganisms and other foreign substance from entering the body. Secretions from skin glands produce an environment unsuitable for some microorganisms. The skin also contains components of the immune system that act against microorganisms. 3. Melanin absorbs ultraviolet light and protects underlying structures from its damaging effects. 4. Hair provides protection in several ways. The hair on the head acts as a heat insulator and protects against ultraviolet light and abrasion. The eyebrows keep sweat out of the eyes, the eyelashes protect the eyes from foreign objects, and hair in the nose and ears prevents dust and other materials from entering. Axillary and pubic hair protect against abrasion. 5. Nails protect the ends of the fingers and toes from damage and can be used in defense. 6. The intact skin play an important role in reducing water loss because its lipids act as a barrier to the diffusion of water.

What are the 6 ways the integumentary system defends the body from harm?

The integumentary system is the body's outer barrier, defending it from harm: 1. The skin protects underlying structures from mechanical damage. Both the dermis and the epidermis play roles in this line of defense, but in different ways. The dermis, particularly the irregular dense connective tissue of the reticular layer, provides structural strength, preventing tearing of the skin. The stratified epithelium of the epidermis protects against abrasion. As the outer cells of the stratum corneum slough off, they are replaced by cells from the stratum basale. Calluses develop in areas subjects heavy friction on pressure. 2. The skin prevents microorganisms and other foreign substance from entering the body. Secretions from skin glands produce an environment unsuitable for some microorganisms. The skin also contains components of the immune system that act against microorganisms. 3. Melanin absorbs ultraviolet light and protects underlying structures from its damaging effects. 4. Hair provides protection in several ways. The hair on the head acts as a heat insulator and protects against ultraviolet light and abrasion. The eyebrows keep sweat out of the eyes, the eyelashes protect the eyes from foreign objects, and hair in the nose and ears prevents dust and other materials from entering. Axillary and pubic hair protect against abrasion. 5. Nails protect the ends of the fingers and toes from damage and can be used in defense. 6. The intact skin play an important role in reducing water loss because its lipids act as a barrier to the diffusion of water.

What does the internal epithelial root sheath have?

The internal epithelial root sheath of the hair follicle has raised edges that mesh closely with the raised edges of the hair cuticle and this arrangement holds the hair in place.

What happens to the keratinocytes of the epidermis?

The keratinocytes of the epidermis are constantly lost at its surface but are also constantly replaced by new keratinocytes moving from the deeper layers.

What happens to the lamellar bodies in the stratum granulosum?

The lamellar bodies, formed as the cells pass through the stratum spinousum, move to the plasma membrane and release their lipid contents into the extracellular space. Inside the keratinocyte, a protein envelope forms beneath the plasma membrane.

What is the last, and most superficial, stratum of the epidermis?

The last, and most superficial, stratum of the epidermis is the stratum corneum.

What is the nail fold?

The lateral and proximal edges of the nail are covered by skin called the nail fold.

What does the length of each stage depend on?

The length of each stage depends on the hair-eyelashes grow for approximately for 30 days and rest for 105 days, whereas the scalp hairs grow for 3 years and rest for 1-2 years.

What do the living cells of the epidermis contain?

The living cells of the epidermis receive nutrients and excrete waste products by the diffusion of substances between the epidermis and the capillaries of the dermis.

What affects the color produced in skin?

The location of pigments and other substances in the skin affects the color produced.

What are the main types of cells within the subcutaneous tissue?

The main types of cells within the subcutaneous tissue are fibroblasts, adipocytes, and macrophages.

What are the major glands of the skin?

The major glands of the skin are the sebaceous glands and the sweat glands.

What are the mammary glands?

The mammary glands are modified apocrine sweat glands located in the breasts. They produce milk.

What does the matrix produce?

The matrix produces both the hair and the internal epithelial root sheath.

What is the medulla?

The medulla is the central axis of the hair, and it consists of two to three layers of cells containing soft keratin.

What is the most common kind of hair loss?

The most common kind of permanent hair loss is "pattern baldness."

What does the epidermis do?

The multiple cell layers of the epidermis protects against the potential damage from abrasion on the skin's surface. In addition, the epidermis reduces water loss through the skin.

What does the nail attach to?

The nail also attaches to the underlying nail bed, which is located between the nail matrix and the hyponychium.

What does the nail bed look like?

The nail bed is visible through the clear nail and appears pink because of blood vessels in the underlying dermis.

What is the nail matrix and bed composed of?

The nail matrix and bed are composed of epithelial tissue, with a stratum basale that gives rise to the cells that form the nail. Though both contribute to the growth of the nail, the nail matrix is thicker than the nail bed and produces nearly all of the nail.

Where does the nail root extend from?

The nail root extends distally from the nail matrix.

What is the nail root covered by?

The nail root is covered by skin, and the nail body is the visible portion of the nail.

What are the nerve endings function of the dermis?

The nerve endings are varied in structure and function. They include (1) free nerve endings for pain, itch, tickle, and temperature sensations; (2) hair follicle receptors for light touch; (3) Pacinian corpuscles for deep pressure; (4) Meissner corpuscles for detecting simultaneous stimulation at two points of the skin; and (5) Ruffini end organs for sensing continuous touch or pressure.

What determines the number of cell layers in each stratum?

The number of cell layers in each stratum and even the number of strata in the skin vary, depending on the location in the body.

What happens to the number of melanocytes as the body ages?

The number of function melanocytes generally decreases; however, in some localized areas, especially not the hands and face, melanocytes increase in number, producing age spots. (Age spots are different from freckles, which are caused by an increase in melanin production, not an increase in melanocyte numbers.) White or gray hairs also appear because of a decrease in or lack of melanin production.

Explain what causes age spots and white hair?

The number of functioning melanocytes generally decreases; however, in some localized areas, especially on the hands and face, melanocytes increase in number, producing age spots (Age spots are different from freckles, which are caused by an increase in melanin production, not an increase in melanocyte numbers.) White or gray hairs also appear because of a decrease in or lack of melanin production.

FIGURE 5.6 Cleavage Lines

The orientation of collagen fibers produces cleavage lines, or tension lines, in the skin.

What do the outermost cells do in the stratified arrangement?

The outermost cells in this stratified arrangement protect the cells underneath, and the deeper, replicating cells replace cells lost from the surface.

What does the papillary layer contain?

The papillary layer also contains blood vessels that supply the overlying epidermis with O2 and nutrients, remove waste products, and aid in regulating body temperature.

Where does the papillary layer derive its name from?

The papillary layer derives its name from projections, called dermal papillae, that extend toward the epidermis.

What is the papillary layer?

The papillary layer is loose connective tissue with thin fibers that are somewhat loosely arranged.

What is fur?

The presence of hair is one of the characteristics of all mammals; if the hair is dense and covers most of the body surface, it is called fur.

What is the main layer of the dermis?

The reticular layer, which is composed of dense irregular connective tissue, is the main layer of the dermis.

What does the secretion of sebum prevent?

The secretion of sebum onto the hair and surrounding skin prevents drying and protects against some bacteria.

Why is heat potentially dangerous to the elderly?

The skin also become drier with age as sebaceous gland activity decreases. Decreases in the activity of sweat glands and the blood supply to the dermis result in a reduced ability to regulate body temperature. Elderly individuals who do not take proper precautions may experience heat exhaustion, which can even lead to death.

What happens to the skin as the body grows old?

The skin also becomes drier with age as sebaceous gland activity decreases. Decreases in the activity of sweat glands and the blood supply to the dermis result in a reduced ability to regulate body temperature.

What are the function of glands on the skin?

The skin has several types of glands that secret materials onto its surface; however, not all are functional in all individuals.

What are the two major tissue layers?

The skin is made up of two major tissue layers, the epidermis and the dermis.

How does the integumentary system provide protection?

The skin is the covering of the body. Though exposed to the external environment, the skin's structure reduces the negative and harmful effects of ultraviolet light. Acting as a barrier, the skin also keeps microorganisms from entering the body and prevents dehydration by reducing water loss.

How is a corn developed?

The skin over bony prominences develop a cone-shaped structure called a corn. The base of the cone is at the surface, but the apex extends deep into the epidermis, and pressure on the corn may be quite painful.

How does the integumentary system regulate temperature?

The skin plays a major role in regulating body temperature through the modulation of blood flow through the skin and the activity of sweat glands.

Where does the skin rest?

The skin rests on the subcutaneous tissue, or hypodermis, a layer of loose connective tissue.

FIGURE 5.1 Skin and Subcutaneous Tissue

The skin, consisting of the epidermis and the dermis, is connected by the subcutaneous tissue to underlying structures. Note the accessory structures (hairs, glands, and arrector pilli), some of which project into the subcutaneous tissue, as well as the large amount adipose tissue in the subcutaneous tissue

What is the stratum basale

The stratum basale, or stratum germinativum is the deepest portion of the epidermis.

What does the stratum corneum consist of?

The stratum corneum consists of cornified cells, which are dead keratinocytes, with a hard protein envelope, filled with the protein keratin.

What is the cuticle?

The stratum corneum of the nail fold grows onto the nail body as the cuticle, or eponychium.

How many layers does the stratum granulosum consist of?

The stratum granulosum consists of two to five layers of somewhat flattened, diamond-shaped cells. The long axes of these cells are oriented parallel to the surface of the skin.

What is the stratum lucidum?

The stratum lucidum is a thin, clear zone above the stratum granulosum.

Where is the stratum lucidum present?

The stratum lucidum is present in only a few areas of the body.

What does the stratum spinousum consist of?

The stratum spinous consist of 8-10 layers of many-sided cells.

What is the function of the dermis?

The structure of the dermis is responsible for most of the strength of the skin. The strength of the dermis is seen in leather, which is produced from the hide (skin) of an animal by removing the epidermis and preserving the dermis in a process called tanning.

Why is the study of keratinization important?

The study of keratinization is important because many skin diseases result from malfunctions in this process. For example, large scales of epidermal tissue are sloughed of in psoriasis. By comparing normal and abnormal keratinization, scientists may be able to develop effective therapies for psoriasis.

What does the subcutaneous tissue attach too?

The subcutaneous tissue attaches the skin to underlying bone and muscle and supplies the skin with blood vessels and nerves.

Describe the structure and functions of the subcutaneous tissue underlying the skin.

The subcutaneous tissue attachs the skin to underlying bone and muscle and supplies the skin with blood vessels and nerves. The subcutaneous tissue consists of loose connective tissue with collagen and elasti ibers. The main types of cells within the subcutaneous tissue are fibroblasts, adipocytes, and macrophages. The subcutaneous tissue, which is not part of the skin, is sometimes called the hypodermis.

What is the subcutaneous tissue used for?

The subcutaneous tissue can be used to estimate total body fat by pinching the skin at selected locations and measuring the thickness of the skin fold and underlying subcutaneous tissue. The thicker the fold, the greater the amount of total body fat.

How is subcutaneous tissue related to skin?

The subcutaneous tissue can be used to estimate total body fat by pinching the skin at selected locations and measuring the thickness of the skin fold and underlying subcutaneous tissue. The thicker the fold, the greater the amount of total body fat.

Name the types of tissue forming the subcutaneous tissue layer.

The subcutaneous tissue consists of loose connective tissue with collagen and elastic fibers.

What does the subcutaneous tissue consist of?

The subcutaneous tissue consists of loose connective tissue with collagen and elastic fibers.

What does the subcutaneous tissue do?

The subcutaneous tissue is not part of the skin or the integumentary system, but it does connect the skin to underlying muscle or bone.

What does the terms thin and thick skin refer to?

The terms thin and thick refer only to the epidermis and should not be used when total skin thickness is considered. It is actually variation in the thickness of the dermis that accounts for most of the difference in total skin thickness.

What type of keratin is found in the skin?

The type of keratin found in the skin is soft keratin.

How many types of injections are there?

There are three types of injections. (1) An individual injection (2) A subcutaneous injection (3) An intramuscular injection.

How many types of sweat glands are there?

There two types of sweat , or sudoriferous glands: eccrine glands and apocrine glands.

What are the changes in hair type?

These changes in hair type at puberty are universal and have biological significance.

How are new keratinocytes produced?

These new keratinocytes are produce when keratinocyte stem cells undergo mitosis in the deepest layer of the epidermis.

Why is using skin from other animals rejected by the body?

These techniques are often unsatisfactory because the body's immune systems recognizes the graft as a foreign substance and rejects it.

How are first-degree burns caused?

They can be caused by sunburn or brief exposure to hot or cold objects, and they heal in a weak or so without scarring.

What does the thick skin have?

Thick skin has all five epithelial strata, and the stratum corneum has many layers of cells.

Where is thick skin found?

Thick skin is found in areas subject to pressure or friction, such as the palm of the hands, the soles of the feet, and the finger tips.

Compare the structure and location of thick and thin skin. Is hair in thick or thin skin.

Thick skin is palms of hands,soles of feet, and the fingertips. The rest of the body is thin skin. Hair is thin skin.

Hyponychium

Thickened portion of the stratum corneum under the free edge of the nail.

How is thin skin different from thick skin?

Thin skin covers the rest of the body and is more flexible than thick skin.

What color are third degree burns?

Third-degree burns appear white, tan, brown, black, or deep cherry-red.

What are third-degree burns surrounded by?

Third-degree burns are often surrounded by first- and second-degree burns. Although the areas that have first- and second-degree burns are painful, the region of third-degree burn is usually painless because the sensory receptors have been destroyed.

Why is the arrangement of epidermal cells important?

This arrangement of epidermal cells has important consequences for skin repair. If the epidermis and the superficial part of the dermis are damaged, the keratinocyte stem cells located in the stratum basal of the undamaged part of the hair follicle can be a source of new epithelium.

What process is similar to the split skin graft?

This is the same process of epidermis formation that occurs following superficial second-degree burns.

Where does the stratum granulosum derive its name from?

This stratum derives its name from the presence of protein granules of keratohyalin, which accumulate in the cytoplasm of the keratinocytes.

What is the stratum corneum composed of?

This stratum is composed of 25 or more layers of dead, overlapping squares cells joined by desmosomes.

Which is thicker dermis or epidermis?

Though the epidermis is stratified, it is not as thick as the dermis.

By combining your understanding of epithelial tissue from chapter 4 with further information about skin structure and pigmentation in this chapter, explain how and why Laura's tan faded in the fall.

To begin, we must identify the important information provided in the question. First, we are told that Laura is spending her summer at the pool, constantly exposed to the sun, and develops a "golden tan." Second, she returns to school in the fall, thus spending less time outside, and her tan fades. We know that sun exposure leads to tanning of the skin, but to answer this question fully we must consider what specifically causes the skin to darken and why tanning is not permanent. We learned in this chapter that melanocytes in the epidermis produce melanin in response to sun exposure and package it in melanosomes. Keratinocytes phagocytize the tips of melanocyte processes containing the melanosomes, and the result is pigmented keratinocytes, and thus darker skin. We can therefore conclude that Laura's skin is darker due to increased sun exposure and increased melanin production during the summer. We also learned in this chapter that the epidermis is a stratified squamous epithelium (described in chapter 4) composed of many layers of cells. Mitosis of cells in the deepest layer (stratum basale) of the epidermis produces new cells, which gradually undergo keratinization and eventually die. At the surface of the skin, keratinized (dead) keratinocytes are sloughed off and replaced by new ones daily. So why did Laura's tan fade? It faded because the older, heavily pigmented keratinocytes were sloughed off each day and replaced with new cells. These new cells, produced after she returned to school, were less pigmented and her skin became a lighter color.

What happens to produce melanin?

To produce melanin, the enzyme tyrosinase converts the amino acid tyrosine to dopaquinone.

How do genetic factors, exposure to sunlight, and hormones determine the amount of melanin in the skin?

To produce melanin, the enzyme tyrosinase converts the amino acid tyrosine to dopaquinone. Dopaquinone can be converted to a variety of related molecules, most of which are brown to black pigments but some of which are yellowish or reddish. Melanin production is determined by genetic factors, exposure to light, and hormones. Genetic factors are primarily responsible for the variations in skin color among different races and among people of the same race. It is interesting to note that the number of melanocytes in the skin is relatively the same for all humans, regardless of race. Racial variations in skin color determined by several major factors: -types of melanin produced -amount of melanin produced -size of melanosomes (melanin-filled vesicles in cells) -number of melanosomes -distribution of melanosomes. Although many genes are responsible for skin color, a single mutation can prevent the manufacture of melanin. Albinism is usually a recessive genetic trait that results from an inability to produce tyrosinase. The result is a deficiency or an absence of pigment in the skin, the hair, and the irises of the eyes. For those individuals who are able to produce melanin, exposure to ultraviolet light darkens the melanin already present in the skin and stimulates melanin production, resulting in tanning. Certain conditions may cause increases in melanin production and therefore changes in pigmentation in areas of the body. During pregnancy, certain hormones, such as estrogen and melanocyte-stimulating hormone, cause the mother's body to increase melanin production, which causes darkening of the nipples, areolae, and genitalia. The cheekbones, forehead, and chest also may darken, resulting in the "mask of pregnancy." In addition, a dark line of pigmentation may appear on the midline of the abdomen. Diseases that cause increased secretion of adrenocorticotropic hormone and melanocyte-stimulating hormone, such as Addison disease, also. caused increased pigmentation.

How are apocrine sweat glands different from eccrine sweat glands

Unlike eccrine sweat glands, apocrine sweat glands do not help regulate temperature in humans.

Why is vitamin D important in the integumentary system?

Vitamin D is important for the regulation of calcium and phosphate homeostasis.

How does vitamin D synthesis begin?

Vitamin D synthesis begins in the skin when it is exposed to ultraviolet light.

List the steps of vitamin D synthesis.

Vitamin D synthesis involves a precursor molecule, 7-dehydrocholesterol which is stored in the skin. 1. When 7-dehydrocholesterol is exposed to ultraviolet light, the precursor molecule is converted into choleacalciferol 2. Cholecalciferol is released into the blood and modified first by the liver and 3. later by the kidney to form active vitamin D3, also called calcitrilol 4.Calcitriol is an important hormone, a chemical messenger that travels through the blood, regulating calcium homeostasis.

Name the locations where cholecalciferol is produced and then modified into vitamin D. What are the functions of vitamin D?

Vitamin D synthesis involves a precursor molecule, 7-dehydrocholesterol which is stored in the skin. When expose to ultraviolet light, the precursor molecule is converted into cholecalciferol. Cholecalciferol is released into the blood and modified first by the liver and later by the kidneys to form active vitamin D3, also called calcitiriol. Calcitriol is an important hormone, a chemical messenger that travels through the blood, regulating calcium homeostasis.

When Sam was first admitted to the burn unit, the nurses carefully monitored his urine output. Why does that make sense in light of his injuries?

We learned that one of the functions of the skin is to reduce water loss. Sam's burns resulted in severe damage to his skin, which most likely led to increased water loss at the injury site, causing dehydration and reduced urine production. We learned that Sam was administered large volumes of fluid to counteract his increased fluid loss. But how much fluid should be given? The amount of fluid given should match the amount that is lost, plus enough to keep the kidneys functioning properly. An adult receiving intravenous fluids should produce 30 to 50 mL of urine per hour, and children should produce 1 mL/kg of body weight per hour. By monitoring Sam's urine output, the nurse can determine if he is getting enough fluids. If his urine output is too low, more fluids can be given.

What happens as the hair is pulled out?

When a hair is pulled out, the internal epithelial root sheath usually comes out as well and is plainly visible as whitish tissue around the root of the hair.

What happens to the blood vessels in the dermis as they constrict?

When blood vessels in the dermis constrict, less warm blood flows from deeper structures to the skin, and heat loss decreases. If body temperature begins to drop below normal, heat can be conserved by a decrease in the diameter of dermal blood vessels.

How does the integumentary system produce vitamin D?

When exposed to ultraviolet light, the skin produces a molecule that can be transformed into the hormonal form of vitamin D, an important regulator of calcium homeostasis.

What happens when we cannot use skin from another part of the body to replace other skin?

When it is not possible or practical to move skin from one part of the body to a burn site, artificial skin or grafts from human cadavers or pigs are used.

What happens when the arrector pili muscles contract?

When the arrector pili muscles contract, however, they pull the follicle into a more perpendicular position, causing the hair to "stand on end."

Why is sweat important?

When the body temperature starts to rise above normal, the sweat glands produce sweat, which evaporates and cools the body.

Lunnula

White, crescent-shaped portion of the nail matrix visible through the proximal end of the nail.

What causes hair to fade?

With age, the amount of melanin in hair can decrease necessarily dominant over light. With age, the amount of melanin in hair can decrease, causing hair color to fade or become white (i.e., no melanin). Gray hair is usually a mixture of unfaded, faded, and white hairs.

What happens in the new cycle?

With this new cycle, a new hair forms to replace the old hair, which falls out of the hair follicle. Thus, losing a hair normally means that the hair is being replaced.

What is within the hair papilla?

Within the hair papilla are blood vessels that provide nourishment to the cells to the matrix.

Explain how woman have more adipose tissue than men.

Women have proportionately more adipose tissue than men, especially over the thighs, buttocks, and breasts, which accounts for some of the differences in body shape between women and men.

What are cornified cells?

dead keratinocytes, with a hard protein envelope, filled with the protein keratin.