introduction to the skin! integumentary system skin (aka- cutaneous membrane) nails hair follicles...
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INTEGUMENTARY SYSTEM
Introduction to the SKIN!Integumentary System
Skin (aka- cutaneous membrane)NailsHair FolliclesSkin Glands
The skin is the largest organ by weightFunctions:
Protective coveringSlows water lossRegulates body temperatureHouses sensory receptorsExcretes small amounts of wasteHelps in vitamin D formation
Tissues of the Skin- Into to Layers2 distinct layers
Epidermis Outer layer Stratified squamous epithelium
Dermis Inner layer Connective tissue Smooth muscle tissue Nervous tissue Blood
Layers are separated by a basement membrane
Tissues of the Skin- HypodermisSubcutaneous layer
Aka- hypodermisNot part of the skinAreolar and adipose tissuesBinds skin to underlying organsHelps insulateContains blood vessels that supply the skin
The dermis and hypodermis lack a sharp boundary
Tissues of the Skin- InjectionsIntradermal injections
Injected into the skinSubcutaneous injections
Injected into the hypodermisAdministered through a hollow needleAlso called hypodermic injections
Transdermal patchesDrug passes into the epidermis through a
permeable membraneMotion sickness, chest pain, blood pressure,
smoking cessation
The Epidermis- Characteristics and FunctionsLacks blood vesselsThickest on palms and soles (0.0-1.4 mm)Other body regions average 0.07-0.12 mmProduction of new epidermal cells balances loss of dead
cells in healthy skinSkin does not completely wear awayCell division increases where skin is rubbed/pressed
regularly Leads to calluses and corns
Protective FunctionsShields against water lossPrevents injuryProtects against harmful chemicalsKeeps out pathogens
The Epidermis-Layers4 main layers:
Stratum corneum Outermost layer Keratinized, dead epithelial cells Keratinization- hardening of cells, waterproof keratin
proteins made and stored in the cellsStratum granulosumStrantum spinosumStratum basale
Deepest layer Able to divide and grown Receive nutrients from dermis Contains melanocytes
The Epidermis- PigmentationThe epidermis contains melanocytes
Produce the pigment melaninFound in the stratum basale
MelaninProvides skin colorAbsorbs UV radiation
Effect of Environmental FactorsSunlight, UV light, X rays
Rapidly darken melanin Stimulate melanocytes to produce more pigment Pigment is transferred to nearby cells
Effect of BloodWell oxygenated blood is bright red
Light-complexioned people may appear pinkDilated vessels redden the skin
Overheated, embarrassed, under the influence of alcohol
Constriction of vesssel cause loss of color Low body temperature, frightened/anxious person
Human Skin ColorDetermined by heredity and environmental &
physiological factorsAll people have ~same number of melanocytesDifferences in skin color result from different
amounts of melanin produced Controlled by several genes More melanin = darker skin
The Dermis- General CharacteristicsThe boundary between the epidermis and dermis
is unevenDermal papillae extend from dermis into ridges
of the epidermisIncreases surface areaMost abundant in hands and feetForm fingerprints
Genes determine general patterns Fetal movement forms distinct characteristics
The dermis binds epidermis to underlying tissuesThickness ranges from 0.5 mm to 3.0 mm
The Dermis- LayersPapillary Layer
Upper layerAreolar connective tissue
Reticular LayerLower layerDense irregular connective tissueGive skin toughness and elasticity
The Dermis- Additional Components
Smooth muscle fibersCan wrinkle the skin (testes)Associated with hair follicles and glands
Skeletal muscle fibersVoluntary movements (facial expressions)
Nerve cellsCarry impulses to dermal muscles and glandsCarry sensory impulses away from sensory
receptors Lamellated corpuscles
In deep dermis Respond to heavy pressure
Tactile corpuscles In upper dermis Sense light touch and texture
Accessory Structures (blood, hair follicles, glands)
Accessory Structures of the Skin-NailsProtective coveringsComponents:
Nail plateNail bed
Skin surfaceLunula
Most actively growing region Produces keratinized, dead cells
Wears away with normal useAnalogous to hoofs and claws of other animals
Accessory Structures of the Skin- Hair FolliclesHair is present on all surfaces except: palms,
soles, lips, nipples and parts of external reproductive organsNot well developed on other surfaces (forehead)
Originates in epidermisNourished by dermisGrow, divide and push older cells toward
surfaceCells become keratinized and dieCreate the hair shaft
Average hair loss is 20-100 hairs a dayA single hair grows 2-6 years and is then
replaced by a completely new hairGenes determine hair color
direct the type and amount of pigment produced by melanocytes
Arrector pili muscles attaches to each hair follicleContraction causes hair to stand upCauses goose bumps
Accessory Structures of the Skin- GlandsSebaceous glands
Associated with hair folliclesOil glandsProduce sebum (oil and cell fragments)Ducts usually empty into hair folliclesActivated by hormonesKeep hairs and skin soft, pliable and
waterproofNot on palms or soles
Sweat glands~2 million per personWidespreadOriginates in deep dermisEccrine glands
Most numerous Abundant on forehead, neck, back Palms and soles
Respond to elevated body temperature Also respond to emotional stress
Apocrine glands Develop a scent as they mix with skin bacteria Activated at puberty React to emotional upset, fright, pain, sexual arousal Most unmberous in axillary regions and groin
Specialized sweat glandsCeruminous glands- ear waxFemale mammary glands- milk