+ Integumentary System (Skin). + Skin Functions Protects deeper tissues from: Mechanical damage (bumps) Chemical damage (acids and bases) Bacterial damage.

+

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 acid

Synthesizes 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 superficial

Stratum basale

Stratum spinosum

Stratum granulosum

Stratum 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 black

Amount 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 structureCollagen 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 pigments

CaroteneOrange-yellow pigment from some

vegetables

HemoglobinRed coloring from blood cells in

dermal capillariesOxygen content determines the

extent of red coloring

+Alterations in Skin Color

Redness (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 disorder

Bruises—hematomas

+Skin Appendages

Sebaceous (Oil) glands

Sudoriferous (Sweat) glands

Hair

Hair follicles

Nails

+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) glands

Produce sweat

Widely distributed in skin

Two types of sudoriferous glandsEccrine

Open 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 Function

CompositionMostly 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 Structures

Free edge

Body: visible attached portion

Root: embedded in skin

Cuticle: 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

+Infections

Athlete’s foot (tinea pedis)Caused by fungal infection

Boils and carbunclesCaused by bacterial infection

Cold soresCaused by virus

+Infections & Allergies

Contact dermatitisExposures cause allergic reaction

ImpetigoCaused by bacterial infection

PsoriasisCause is unknownTriggered by trauma,

infection, stress