INTEGUMENTARY SYSTEM

Integumentary System

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

Integument

means covering, and the integumentary system is one of the mor familiar systems of the body to everyone because it covers the outside of the body and is easily observed

Protection

The skin provides protection against abrasion and ultraviolet light.

Protection

It also prevents microorganisms from entering the body and reduces water loss, thus preventing dehydration

Sensation

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

Vitamin D production

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

Temperature regulation

The amount of blood flow beneath the skin’s surface and the activity of sweat glands in the skin both help regulate body temperature

Excretion

Small amounts of waste products are lost through the skin and in gland secretions

epidermis and dermis

The skin is made up of two major tissue layers

Epidermis

is the most superficial layer of skin

Epidermis

It is a layer of epithelial tissue that rests on the dermis.

Dermis

Dense connective tissue that forms the deep layer of the skin; responsible for the structural strength of the skin

Epidermis

Outer portion of the skin formed of epithelial tissue that rests on the dermis; resists abrasion and forms a permeability barrier

Subcutaneous tissue

under the skin; same tissue as the hypodermis

Subcutaneous tissue

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

Epidermis

stratified squamous epithelium; in its deepest layers, new cells are produced by mitosis

Epidermis

many cells of this prevent water loss and resist abrasion

Keratinization

Production of keratin and changes in the structure and shape of epithelial cells as they move to the skin surface

Outermost cells of epidermis

protect the cells underneath, and the deeper, replicating cells replace cells lost from the surface

Keratinization

reflects the fact that the cells become filled with the protein keratin which makes them more rigid and durable

Keratin

Protein that accumulates in cells of nails, hair, and the superficial layers of the epidermis of the skin

Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum

Five layers that divides the epidermis into layers

Stratum basale

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

Stratum spinosum

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

Flat and diamond-shaped

shapes of the cells of the stratum granulosum

Dermal papillae

project toward the epidermis

Stratum lucidum

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

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

Thick and thin skin

only refer to the number of epidermal strata and not to the overall thickness of the skin, which is determined by the dermis

Stratum corneum

the most superficial stratum of the epidermis

Stratum corneum

consists of dead squamous cells filled with keratin

Stratum corneum

cells are also coated and surrounded by lipids released from the lamellar bodies of the skin cells

Stratum corneum

these lipids act as waterproofing material, thereby preventing fluid loss through the skin

Stratum corneum

composed of 25 or more layers of dead squamous cells joined by desmosomes

Callus

thickening of the stratum corneum of skin in response to friciton; the zone of tissue repair between fragments of a broken bone

Corn

Thickening of the stratum corneum of the skin over a bony projection in response to friction or pressure

Dermis

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

Dermis

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

Superficial papillary layer and deep reticular layer, reticular layer

Two layers of dermis

Superficial papillary layer

composed of loose, connective tissue

Deep reticular layer

composed of dense irregular connective tissue

Reticular layer

thicker, main layer of the dermis

Collagen and elastic fibers of the reticular layer

responsible for the strength of the dermis

Collagen fibers of the dermis

oriented in many different directions and can resist stretch

Collagen fibers of the dermis

produces cleavage lines, or tension lines, in the skin, and the skin is most resistant to stretch alone these lines

Stretch marks

can develop when a person increases in size quite rapidly

Dermal papillae

projection of the papillary layer of the dermis which extend toward the epidermis

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

Intradermal injection

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

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

delivers material to the blood faster than intradermal or subcutaneous injection

Intramuscular injection

is accomplished by inserting a long needle at a 90-degree angle to the skin

Intramuscular injection

are used for most vaccines and certain antibiotics

Pigments in the skin, blood circulating, thickness of the stratum corneum

several factors that determine skin color

Melanin

Brown to black pigment responsible for skin and hair color

Melanin

provides protection against ultraviolet light from the sun

Melanin

is produced by melanocytes

Melanocytes

are irregularly shaped cells between the stratum basale and the stratum spinosum

Melanosomes

pigment granule produced by melanocytes

Skin cancer

the most common type of 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

Squamous cell carcinoma

develops from cells immediately superficial to the stratum basale

Squamous cell carcinoma

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

Malignant melanoma

a rare form of cancer that arises from melanocytes, usually in a preexisting mole

Melanoma

can appear as a large, flat, spreading lesion or as a deeply pigmented nodule

Metastasis

common and unless diagnosed and treated early in development, this cancer is often fatal

Carotene

a yellow pigment found in plants such as squash and carrots

Carotene

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

Carotenoderma

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

Hypodermis

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

Subcutaneous tissue

loose connective tissue, including adipose tissue that contains about half the body’s stored lipids

Subcutaneous tissue

can be used to estimate total body fat

21%-30%

The acceptable percentage of body fat for females

13%-25%

The acceptable percentage of body fat for males

Hair

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

an invagination of the epidermis that extends deep into the dermis

Shaft of the hair

protrudes above the surface of the skin

Root

below the surface of the hair

Hair bulb

is the expanded base of the root

Cortex

outer part of an organ such as the brain, kidney, adrenal gland, or hair

Medulla

Center, or core, of an organ, such as the adrenal gland, kidney, or hair

Cuticle

single layer of overlapping cells that holds the hair in the hair follicle

Hair bulb

rests on the hair papilla

Hair papilla

an extension of the dermis that protrudes into the hair bulb

Arrector pili

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

Contraction of the 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

Goose bump

raised area of skin

Sebaceous and sweat

major glands of the skin

Sebaceous gland

gland of the skin that produces sebum; usually associated with a hair follicle

Sebaceous gland

simple, branched acinar glands

Sweat glands

secretory organ that produces a watery secretion, called sweat, that is released onto the surface of the skin; some sweat glands, however, produce an organic secretion

Glands

produce sebum

Sebum

an oily, white substance rich in lipids

Sebum

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

Eccrine and apocrine

two kinds of sweat glands

Eccrine sweat glands

simple, coiled, tubular glands and release sweat by merocrine secretion

Eccrine sweat glands

located in almost every part of the skin but are most numerous in the palms and soles

Eccrine sweat glands

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

Emotional sweating

can also occur in the palms, soles, armpits, and other places