+
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