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