ANATOMY AND PHYSIOLOGY

Integumentary System

Skin

Called cutaneous membrane or integumentIntegument and its appendages form the

integumentary system Hair Nails

Largest organ in human body Covers entire surface of the human body

Skin has two distinguished regions; three layers Hypodermis Dermis Epidermis

Skin

Functions Protection

Internal organs Waterproof, cushions, and insulates Protects against heat, bacteria, and UV rays

Regulates body heat Facilitates water retention and loss Site of sensory receptors

Skin—Hypodermis

A subcutaneous (below the skin) tissue layer Also called superficial fascia Not considered skin

Fatty tissue which stores fat and anchors skinDifferent patterns of fat accumulation in men

and womenConnects to underlying muscle

tissue when muscle is present ifnot connects directly to bone

Skin—Epidermis

The outer and thinner region of skinMade of stratified squamous epithelium

divided into five separate layers Stratum basale—single row of cells attached to dermis;

youngest cells Stratum spinosum—bundles of protein that resist

tension Stratum granulosum—layers of flattened cells

producing keratin (hair and nails are composed of it) Stratum lucidum—only found on the palms and soles Stratum corneum—thick layers made of dead cells

Avascular and made of tightly-packed cells

Skin—Epidermis

Stratum basale Cells of this layer not supplied with nutrients and

oxygen, so they die off Contains melanocyte cells that produce melanin,

which gives skin its color.Sensory nerves are found in the stratum

basale Free nerve endings – supply pain and temperature

sensations to the brain Tactile cells (Merkel cells) – signal the brain that an

object has touched the skin

Skin - Dermis

Strong and flexible connective tissueContains rich supply of nerves and vesselsCritical role in temperature regulation (the

vessels)Two layers

Papillary – areolar connective tissue; includes dermal papillae, which is responsible for fingertip patterns

Reticular – network of collagen and reticular fibers

Hair

Found on all body parts except the palms, soles, lips, nipples, and portions of the external reproductive organs

Projects from structures called hair follicles (formed from epidermis cells) Hair follicles are located in the dermis

Each hair has oil glands also calledsebaceous glands that empties intothe hair follicle

Hair

Functions Warmth Sense Protection for scalp

Made of hardened keratinThree concentric layers

Medulla—core Cortex—surrounds medulla Cuticle—overlapping single layers

Nails

Grow from special epithelial cells at base of nail called nail root

Cells become keratinized as they grow out over nail bed

Visible portion of nail is called nail bodyCuticle is a fold of skin that

hides nail rootThe whitish color of the

“half-moon” shaped base is called a lunula

Glands—Sweat

Also called sudoriferous glandsPresent in all regions of skinTwo types

Apocrine glands Open into hair follicles in the anal region, groin, and armpits Glands begin to secrete after puberty

Eccrine glands Open onto surface of the skin Become active when person is hot to lower body

temperature Sweat is mostly water, salts, and a waste substance called

urea Ears have modified sweat glands that produce earwax

Glands—Sebaceous

Most sebaceous glands are associated with hair follicles

Glands secrete sebum, which lubricate hair and skin and kill bacteria on skin surface

Glands may fail to secrete sebum and accumulation of sebum causes whiteheads and blackheads to appear on skin surface

Most common form of acne, Acne vulgaris, is the inflammation of sebaceous glands

Glands—Other

Mammary Glands Modified apocrine sweat glands Produce milk after childbirth

Ceruminous Glands Modified apocrine sweat

glands Secrete earwax, or cerum

Disorders of the Skin

Athlete’s Foot Caused by a fungal infection that involves skin of the toes and

solesImpetigo

Highly contagious disease that is caused by bacterial infection that results in pustules

Eczema Inflammation of the skin caused by sensitivity to certain chemicals,

fabrics, and dryness or heatDandruff

Skin disorder caused by an accelerated rate of keratinization in certain areas of the scalp – causes flaking and itching.

Hives An allergic reaction characterized by the appearance of reddish,

elevated patches and itching.

Disorders—Skin Cancer

Categorized as melanoma or non-melanoma Begins with mutation of skin cell DNA

Non-melanoma Basal cell carcinoma

Most common type of skin cancer Begins when ultraviolet radiation causes epithelial basal cells to

form a tumor Squamous cell carcinoma

Begins in the epidermis Triggered by excessive UV exposure

Melanoma Associated with skin aging, UV exposure, and overproduction of

melanin in melanocytes which causes an unusual mole Most dangerous type of skin cancer

Disorders—Burns

Burns Catastrophic loss of body fluids Dehydration and fatal circulatory shock Infection

Types First degree

Occurs in epidermis Most common—skinburn

Second degree Occurs in epidermis and upper dermis Commonly blisters

Third degree Occurs in epidermis, dermis, and sometimes as deep as

hypodermis Worst and most dangerous type of burn

Wounds and Healing

A wound is characterized by redness, swelling, heat, and pain

A wound that punctures a blood vessel will fill with blood Chemicals cause the blood to clot Blood clots will harden and create a scab when

exposed to air Fibroblasts pull skin together to regenerate tissue Scar tissue is a tissue composed of many collagen

fibers

Aging

As skin ages, the rate of cell reproduction decreases Dermis becomes thinner and is held less tightly to the

epidermis causing loose skinWrinkling

Epidermis is loose Fibers are fewer and scarce Hypodermis has less padding

Melanocytes decrease causing hair to turn gray and skin becomes paler

Many changes due to sun damage

Homeostasis

Used to regulate water loss and gainRegulates body temperature as wellDisorders

Hypothermia Body temperature falls below normal

Hyperthermia Body temperatures rises above normal