+

Integumentary System(Skin)

+Skin FunctionsProtects deeper tissues from:

Mechanical damage (bumps)Chemical damage (acids and bases)Bacterial damage Ultraviolet radiation (sunlight)Thermal damage (heat or cold)Desiccation (drying out)

Aids in body heat loss or heat retention as controlled by the nervous system

Aids in excretion of urea and uric acidSynthesizes vitamin D

+Skin Structure Epidermis—outer layer

Stratified squamous epithelium Can become keratinized (hardened by keratin) to

prevent water loss Avascular (no blood supply of its own) Most cells are keratinocytes (cells that produce

keratin – a fibrous protein that makes the epidermis tough)

Dermis Dense connective tissue

Subcutaneous tissue (hypodermis) is deep to dermis Not technically part of the skin Anchors skin to underlying organs Composed mostly of adipose tissue

+Layers of the Epidermis Can contain up to 5 of these layers (strata) Stratum basale (stratum germinativum)

Deepest layer of epidermis Lies next to dermis Wavy borderline with the dermis anchors the two

together Cells undergoing mitosis (cell division) Daughter cells are pushed upward to become the

more superficial layers Stratum spinosum Stratum granulosum

Cells become flatter and more full of keratin

+Layers of the Epidermis (cont’d)

Stratum lucidum Formed from dead cells of the deeper strata Occurs only in thick, hairless skin of the

palms of hands and soles of feet Stratum corneum

Outermost layer of epidermis Shingle-like dead cells are filled with keratin

(protective protein prevents water loss from skin)

+Summary of layers from deepest to most superficialStratum basaleStratum spinosumStratum granulosumStratum lucidum (thick, hairless skin

only)Stratum corneum

+Melanin

Pigment (melanin) produced by melanocytes

Melanocytes are mostly in the stratum basale

Color is yellow to brown to blackAmount of melanin produced depends

upon genetics and exposure to sunlight

+DermisTwo layers

Papillary layer (upper dermal region)Projections called dermal papillae

Some contain capillary loopsOthers house pain receptors and

touch receptorsReticular layer (deepest skin layer)

Blood vesselsSweat and oil glandsDeep pressure receptors

+Dermis (cont’d)Overall dermis structure

Collagen and elastic fibers located throughout the dermisCollagen fibers

give skin its toughness

Elastic fibers give skin elasticity

Blood vessels play a role in body temperature regulation

+Normal Skin Color DeterminantsMelanin

Yellow, brown, or black pigmentsCarotene

Orange-yellow pigment from some vegetables

HemoglobinRed coloring from blood cells in

dermal capillariesOxygen content determines the

extent of red coloring

+Alterations in Skin ColorRedness (erythema)—due to

embarrassment, inflammation, hypertension, fever, allergy, or conditions like rosacea

Pallor (blanching)—due to emotional stress such as fear, anemia, low blood pressure, impaired blood flow to an area

Jaundice (yellowing)—liver disorderBruises—hematomas

+Skin Appendages

Sebaceous (Oil) glandsSudoriferous (Sweat) glandsHairHair folliclesNails

+Sebaceous (oil) glands

Produce oil (sebum)Lubricant for skinPrevents brittle hairKills bacteria

Most have ducts that empty into hair follicles; others open directly onto skin surface

Glands are activated at puberty

+Sudoriferous (Sweat) glandsProduce sweat Widely distributed in skinTwo types of sudoriferous glands

EccrineOpen via duct to pore on skin surfaceProduce sweat (clear)

Apocrine (Begin to function at puberty)Ducts empty into hair folliclesRelease sweat that also contains fatty

acids and proteins (milky/yellowish color)

+Sweat and its FunctionComposition

Mostly waterSalts and vitamin CSome metabolic wasteFatty acids and proteins (apocrine only)

FunctionHelps dissipate excess heatExcretes waste productsAcidic nature inhibits bacteria growth

Odor is from associated bacteria

+Hair Produced by hair follicle Consists of hard keratinized epithelial cells Melanocytes provide pigment for hair color Hair grows in the matrix of the hair bulb in the stratum

basale Hair anatomy

Central medulla Cortex surrounds medulla Cuticle on outside of cortex

Most heavily keratinized

+Associated Hair Structures Hair follicle

Dermal and epidermal sheath around hair root

Arrector pili muscle Smooth muscle Pulls hair upright when cold or

frightened Sebaceous gland Sudoriferous gland

+Nails

Scale-like modifications of the epidermisHeavily keratinized

Stratum basale extends beneath the nail bedResponsible for growth

Lack of pigment makes them colorless

+Nail StructuresFree edgeBody: visible attached

portionRoot: embedded in

skinCuticle: proximal nail

fold that projects onto the nail body

+Skin Homeostatic Imbalances

Burns

+Burns

Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals

Associated dangersDehydrationElectrolyte imbalanceCirculatory shock

+Rule of Nines

Way to determine the extent of burns

Body is divided into 11 areas for quick estimation

Each area represents about 9 percent of total body surface area

+Severity of BurnsFirst-degree burns

Only epidermis is damagedSkin is red and swollen

Second-degree burnsEpidermis and upper dermis

are damagedSkin is red with blisters

Third-degree burnsDestroys entire skin layer;

burned area is painlessBurn is gray-white or black

+Critical Burns

Burns are considered critical ifOver 25 percent of body has second-

degree burnsOver 10 percent of the body has third-

degree burnsThere are third-degree burns of the

face, hands, or feet

+Skin Homeostatic Imbalances

Infections

+InfectionsAthlete’s foot (tinea pedis)

Caused by fungal infection

Boils and carbunclesCaused by bacterial infection

Cold soresCaused by virus

+Infections & AllergiesContact dermatitis

Exposures cause allergic reactionImpetigo

Caused by bacterial infectionPsoriasis

Cause is unknownTriggered by trauma,

infection, stress