ap chap 5

integumentary system

integumentary system

• is one of the more familiar systems of the body to everyone because it covers the outside of the body and is easily observed

• consists of the skin and accessory structures, such as hair, glands, and nails

1. protection

2. sensation

3. vitamin d production

4. temperature regulation

5. excretion

Major functions of the integumentary system

1. epidermis

2. dermis

skin is made up of two major tissue layers

epidermis

• is the most superficial layer of skin.

• provides protection

dermis

• epidermis is a layer of epithelial tissue that rests on the —, which is a layer of dense connective tissue

• is responsible for most of the skin’s structural strength

subcutaneous tissue

• the skin rests on the — which is also a layer of connective tissue.

• — is not part of the skin, but it does connect the skin to underlying muscle or bone

stratified squamous epithelium

The epidermis is —; in its deepest layers,

mitosis

epidermis new cells are produced by —

keratinization

(epidermis) During their movement, the cells change shape and chemical composition, a process called —

keratin

The term keratinization reflects the fact that the cells become filled with the protein —-, which makes them more rigid and durable.

strata

Although keratinization is a continuous process, distinct cellular characteristics can be recognized. These characteristics are used to divide the epidermis into layers called —

1. stratum basale

2. stratum spinosum

3. stratum granulosum

4. stratum lucidum

5. stratum corneum

From the deepest to the most superficial, the five strata are the

stratum basale

• consists of cuboidal or columnar cells that undergo mitotic divisions about every 19 days.

• One daughter cell becomes a new — cell and can divide again.

• The other daughter cell is pushed toward the surface, a journey that takes about 40–56 days.

• As cells move to the surface, changes in the cells produce intermediate strata

stratum spinosum

cells of — take on a flattened appearance and accumulate lipid-filled vesicles called lamellar bodies

stratum granulosum

• cells of — are flat and diamond shaped.

• The cells accumulate more keratin and release the contents of the lamellar bodies to the extracellular space.

• The cells’ nuclei and organelles degenerate, and the cells die, giving this layer its characteristic grainy appearance

stratum lucidum

• is a thin, clear zone between the stratum granulosum and stratum corneum.

• is present in certain areas of the body.

• The cells of this stratum no longer have nuclei or organelles, and as a result, the cells stain more lightly

thick skin

has all five strata and is found in areas subject to pressure or friction, such as the palms of the hands, the soles of the feet, and the fingertips

thin skin

lacks the stratum lucidum and covers the rest of the body.

stratum corneum

• is the most superficial stratum of the epidermis. It consists of dead squamous cells filled with keratin. Keratin gives the — its structural strength.

• The — cells are also coated and surrounded by lipids released from the lamellar bodies of the skin cells.

• These lipids act as waterproofing material, thereby preventing fluid loss through the skin.

dandruff

Excessive sloughing of stratum corneum cells from the surface of the scalp is called —

callus

In skin subjected to friction, the number of layers in the stratum corneum greatly increases, producing a thickened area called a

corn

Over a bony prominence, the stratum corneum can thicken to form a cone-shaped structure called a —

dermis (2)

• is composed of dense collagenous connective tissue containing fibroblasts, adipocytes, and macrophages.

• Nerves, hair follicles, smooth muscles, glands, and lymphatic vessels extend into the

Collagen and elastic fibers

— are responsible for the strength of the dermis.

collagen fibers

The —-of the dermis are oriented in many different directions and can resist stretch

cleavage lines

However, more collagen fibers are oriented in some directions than in others. This produces — or tension lines, in the skin, and the skin is most resistant to stretch along these lines

across

An incision made — the cleavage lines is likely to gap and produce considerable scar tissue,

parallel

but an incision made — with the cleavage lines tends to gap less and produce less scar tissue

stretch marks

If the skin is overstretched for any reason, the dermis can be damaged, leaving lines that are visible through the epidermis. These lines, called —-, can develop when a person increases in size quite rapidly

dermal papillae

• The upper part of the dermis has projections called — which extend toward the epidermis

• Recall that the epidermis lacks blood vessels; however, the — contain many blood vessels.

• Blood flow through these vessels supplies the overlying epidermis with nutrients, removes waste products, and helps regulate body temperature.

friction ridges

• The dermal papillae in the palms of the hands, the soles of the feet, and the tips of the digits are arranged in parallel, curving ridges that shape the overlying epidermis into patterns called —

• the impressions left on surfaces by these — are fingerprints and footprints

injection

• An — delivers substances, such as medicines, to the body by puncturing the skin.

• Substances are administered at different depths in the skin, depending on how quickly the material needs to enter the blood

intradermal injection

• An— delivers material to the blood slowly and is administered by drawing the skin taut and inserting a small needle at a shallow angle into the dermis;

• an example is the tuberculin skin test

subcutaneous injection

• A — is achieved by pinching the skin to form a “tent” and inserting a short needle into the adipose tissue of the subcutaneous tissue;

• an example is an insulin injection.

intramuscular injection

• An—delivers material to the blood faster than intradermal or subcutaneous injections.

• is accomplished by inserting a long needle at a 90-degree angle to the skin into a muscle deep to the subcutaneous tissue.

• — are used for most vaccines and certain antibiotics.

1. pigments in the skin

2. blood circulating through the skin

3. thickness of the stratum corneum

Several factors determine skin color:

melanin

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

• provides protection against ultraviolet light from the sun

melanocytes

• Melanin is produced by —

• are irregularly shaped cells located between the stratum basale and the stratum spinosum.

• They have many long processes that extend between the epithelial cells of the deep part of the epidermis

melanosomes

• Within melanocytes, the Golgi apparatuses package melanin into vesicles called

• — move into the cell processes of the melanocytes.

albinism

is a recessive genetic trait that causes a deficiency or an absence of melanin, resulting in fair skin, white hair, and unpigmented irises in the eyes.

skin cancer

• is the most common type of cancer.

• Although chemicals and radiation (x-rays) are known to induce cancer, the development of — most often is associated with exposure to ultraviolet (UV) light from the sun

1. basal cell carcinoma

2. squamous cell carcinoma

3. malignant melanoma

3 main types of skin cancer

basal cell carcinoma

• — the most frequent type, begins with cells in the stratum basale and extends into the dermis to produce an open ulcer

• Surgical removal or radiation therapy cures this type of cancer.

• Fortunately, there is little danger that this type of cancer will spread, or metastasize, to other areas of the body.

squamous cell carcinoma

• develops from cells immediately superficial to the stratum basale.

• Normally, these cells undergo little or no cell division, but in —the cells continue to divide as they produce keratin. The typical result is a nodular, keratinized tumor confined to the epidermis

• If untreated, the tumor can invade the dermis, metastasize, and cause death

malignant melanoma

• is a rare form of skin cancer that arises from melanocytes, usually in a preexisting mole.

• A mole is an aggregation, or “nest,” of melanocytes. The melanoma can appear as a large, flat, spreading lesion or as a deeply pigmented nodule

1. UVA

2. UVB

Ultraviolet light is classified into two types based on their wavelengths:

UVA

• has a longer wavelength

• Exposure to — causes most tanning of the skin but is associated with the development of malignant melanoma

UVB

Exposure to—causes most burning of the skin and is associated with the development of basal cell and squamous cell carcinomas.

estrogen and melanocyte-stimulating hormone

certain hormones, such as —, cause an increase in melanin production during pregnancy in the mother, darkening the nipples, the pigmented circular areas around the nipples, and the genitalia even more.

cyanosis

• A decrease in blood flow, as occurs in shock, can make the skin appear pale.

• A decrease in the blood O2 content produces a bluish color of the skin, called

birthmarks

are congenital (present at birth) disorders of the blood vessels in the dermis.

carotene

• is a yellow pigment found in plants such as squash and carrots.

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

• — is lipid-soluble, and when consumed it accumulates in the lipids of the stratum corneum and in the adipocytes of the dermis and subcutaneous tissue.

• If large amounts of carotene are consumed, the skin can become quite yellowish

subcutaneous tissue

• Just as a house rests on a foundation, the skin rests on the — or hypodermis

• The — is not part of the skin but instead attaches the skin to underlying bone and muscle and supplies it with blood vessels and nerves

• is loose connective tissue

adipose tissue

• The subcutaneous tissue is loose connective tissue, including —that contains about half the body’s stored lipids.

• — in the subcutaneous tissue functions as padding and insulation, and it is responsible for some of the differences in appearance between males and females as well as between individuals of the same sex

21% to 30%

The acceptable percentage of body fat varies from — for females

13% to 25%

The acceptable percentage of body fat varies from — for males

hair

In humans, — is found everywhere on the skin, (except on the palms, the soles, the lips, the nipples, parts of the genitalia, and the distal segments of the fingers and toes)

hair follicle

• Each hair arises from a —, an invagination of the epidermis that extends deep into the dermis

• The vase is like the —- and the flower stem is like the hair

shaft

The — of the hair protrudes above the surface of the skin,

root

whereas the — of the hair is below the surface.

hair bulb

The — is the expanded base of the root.

medulla

A hair has a hard cortex, which surrounds a softer center the —

cuticle

The cortex is covered by the—, a single layer of overlapping cells that holds the hair in the hair follicle.

hair papilla

• Hair is produced in the hair bulb, which rests on the —

• — is an extension of the dermis that protrudes into the hair bulb.

• Blood vessels within the — a supply the hair bulb with the nourishment needed to produce the hair.

growth and rest stage

Hair is produced in cycles of

growth stage

• During the—, a hair is formed by epithelial cells within the hair bulb.

• These cells, like the cells of the stratum basale in the skin, divide and undergo keratinization.

• The hair grows longer as these cells are added to the base of the hair within the hair bulb. Thus, the hair root and shaft consist of columns of dead keratinized epithelial cells

resting stage

• During the —, growth stops and the hair is held in the hair follicle.

• When the next growth stage begins, a new hair is formed and the old hair falls out.

arrector pili

• Associated with each hair follicle are smooth muscle cells called the—

• Contraction of the — causes the hair to become more perpendicular to the skin’s surface, or to “stand on end

goose bump

contraction of arrector pili causes the hair to become more perpendicular to the skin’s surface, or to “stand on end,” and it produces a raised area of skin called a —

sebaceous glands and sweat glands

major glands of the skin

sebaceous glands

• — are simple, branched acinar glands

• Most are connected by a duct to the superficial part of a hair follicle.

sebum

• sebaceous glands produce —

• oily, white substance rich in lipids.

• — is released by holocrine secretion and lubricates the hair and the surface of the skin, which prevents drying and protects against some bacteria.

1. eccrine sweat glands

2. apocrine sweat glands

2 kinds of sweat glands

eccrine glands

• are simple, coiled, tubular glands and release sweat by merocrine secretion.

• — are located in almost every part of the skin but most numerous in the palms and soles. They produce a secretion that is mostly water with a few salts

• — have ducts that open onto the surface of the skin through sweat pores.

apocrine sweat glands

• are simple, coiled, tubular glands that produce a thick secretion rich in organic substances.

• These substances are released primarily by merocrine secretion, though some glands demonstrate holocrine secretion.

• They open into hair follicles, but only in the armpits and genitalia.

• — become active at puberty because of the influence of reproductive hormones

body odor

The organic secretion, which is essentially odorless when released, is quickly broken down by bacteria into substances responsible for what is commonly known as —

nail

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

nail body

The visible part of the nail is the

nail root

the part of the nail covered by skin

cuticle

or eponychium, is stratum corneum that extends ti the nail bed

nail matrix

• The nail root extends distally from the —

• is thicker than the nail bed and produces most of the nail

nail bed

The nail also attaches to the underlying —, which is located distal to the nail matrix.

lunula

A small part of the nail matrix, the— can be seen through the nail body as a whitish, crescent-shaped area at the base of the nail.

vitamin D

• When the skin is exposed to ultraviolet light, a precursor molecule of — is formed.

• The precursor is carried by the blood to the liver, where it is modified, and then to the kidneys, where the precursor is modified further to form active—

37°C (98.6°F)

Body temperature normally is maintained at about —

excretion

the removal of waste products from the body. In addition to water and salts, sweat contains small amounts of waste products, such as urea, uric acid, and ammonia

jaundice

• A yellowish skin color, called — can occur when the liver is damaged by a disease, such as viral hepatitis.

• Normally, the liver secretes bile pigments, breakdown products of worn-out red blood cells, into the small intestine.

• Bile pigments are yellow, and their buildup in the blood and tissues can indicate impaired liver function

burn

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

partial-thickness burns

• — part of the stratum basale remains viable, and regeneration of the epidermis occurs from within the burn area, as well as from the edges of the burn.

• — are divided into first- and second-degree burns.

first-degree burns

• — involve only the epidermis and are red and painful.

• Slight edema or swelling, may be present. They can be caused by sunburn or brief exposure to very hot or very cold objects, and they heal without scarring in about a week.

Second-degree burns

• —- damage both the epidermis and the dermis. If dermal damage is minimal, symptoms include redness, pain, edema, and blisters.

• Healing takes about 2 weeks, and no scarring results.

• However, if the burn goes deep into the dermis, the wound appears red, tan, or white; can take several months to heal; and might scar.

full-thickness burns or third-degree burns

• — the epidermis and the dermis are completely destroyed, and recovery occurs from the edges of the burn wound.

• — often are surrounded by areas of first- and second-degree burns.

• the region of — is usually painless because sensory receptors in the epidermis and dermis have been destroyed.

• appear white, tan, brown, black, or deep cherry red.

fourth-degree burns

• are extremely severe burns that affect tissues deeper than the subcutaneous tissue.

• These burns often damage muscle, bone, and other tissues associated with them.

• are painless due to the destruction of the pain receptors.

• Because these burns are so severe, amputation or complete removal of the damaged tissue is required.

split skin graft

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

• To prevent these complications and to speed healing,— are often performed.

• In a procedure called a —, the epidermis and part of the dermis are removed from another part of the body and placed over the burn.