CHAPTER 4
CHAPTER 4SKIN AND BODY MEMBRANES
Body MembranesBody membranes cover surfaces, line body cavities,
and form protective sheets around organsFall into two major
groups:1. epithelial membranesinclude cutaneous, mucous, and serous
membranes2. connective tissue membranesRepresented by synovial
membranes
Body MembranesThe functions of body membranes:1. line or cover
body surfaces2. protect body surfaces3. lubricate body surfaces
CLASSIFICATION OF BODY MEMBRANES
Epithelial MembranesEpithelial membranes (covering and lining
membranes) include cutaneous membrane, mucous membranes, and serous
membranes
Epithelial MembranesCalling these epithelial is inaccurateDo
contain an epithelial sheet, but it is always combined with an
underlying layer of connective tissueThese are simple organs
Cutaneous MembranesCutaneous Membrane: your skinExposed to
airDry membraneThe superficial epidermis keratinizing stratified
squamous epitheliumThe underlying dermis mostly dense connective
tissue
Mucous MembranesSurface epitheliumtype depends on siteUnderlying
loose connective tissue (lamina propia)Lines all body cavities that
open to the exterior body surfaceOften adapted for absorption and
secretion
Serous MembranesSurface simple squamous epitheliumUnderlying
areolar connective tissueLines open body cavities that are closed
to the exterior of the bodySerous layers separated by serous
fluid
Serous MembranesSpecific serous membranesPeritoneumAbdominal
cavityPleuraAround the lungsPericardiumAround the heart
Connective Tissue MembranesSynovial membraneConnective tissue
onlyLines fibrous capsules surrounding jointsProvide:Smooth surface
Secrete lubricating fluid
Synovial Membrane
Connective Tissue MembranesSynovial membraneAlso line bursae and
tendon sheathsCushion organs moving against each other during
muscle activity
THE INTEGUMENTARY SYSTEM (SKIN)
Integumentary SystemSkin (cutaneous membrane)Skin
derivativesSweat glandsOil glandsHairsNails
Skin FunctionsProtects deeper tissues from:Mechanical
damageChemical damageBacterial damageThermal damageUltraviolet
radiationDesiccation
Skin FunctionsThe uppermost layer of the skin is full of keratin
and is cornified, or hardened, to help prevent water loss from the
body surface
Skin FunctionsProtects deeper tissuesAids in heat
regulationCapillary network and sweat glandsAids in excretion of
urea and uric acidUrea, salts, waterSynthesizes Vitamin DModified
cholesterol molecules in the skin are converted to Vitamin D by
sunlightCutaneous Sensory ReceptorsTiny sensors detect touch,
pressure, temperature and pain
Skin StructureEpidermis outer layerStratified squamous
epitheliumOften keratinizedDermisDense connective tissue
Skin Structure
Skin StructureEpidermis and dermis are firmly connectedA burn or
friction may cause them to separateInterstitial fluid accumulates,
forms blister
Skin StructureDeep to the dermis is the hypodermis (subcutaneous
tissue)Not part of the skinAnchors skin to underlying
organsComposed mostly of adipose tissue
Skin Structure
EPIDERMIS
EpidermisComposed of up to five layers:Stratum basaleStratum
spinosumStratum granulosumStratum lucidumStratum corneum
EpidermisMost cells of the epidermis are keratinocytes: keratin
cells
Epidermis Stratum basaleDeepest cell layer in epidermisLies
closest to the dermisReceive the most nourishment, through
diffusion, from the dermisCells are undergoing mitosis (also called
the stratum germinativum)Pushed upward from this layer
Epidermis Stratum basale
Epidermis stratum spinsosum and stratum granulosumAbove the
stratum basale is the stratum spinosum and then the stratum
granulosumFlatter, more keratinized
Epidermis Stratum lucidumAbove the stratum granulosum is the
stratum lucidumClear layer full of dead skin cellsNot present in
all skin regionsThick, hairless areas (palms, soles)High in
keratinFar from blood supply
Epidermis Stratum corneumOutermost layerAccounts for of
epidermal thicknessShingle-like dead cellsCompletely filled with
keratinAlso called cornified or horny cells
Epidermis stratum corneumThe stratum corneum rubs and flakes off
slowly as dandruffThe stratum corneum is replaced quickly by rising
cells from the stratum basaleWe have an entirely new epidermis
every 25-45 days.
Epidermis - MelaninMelanin: pigment that ranges in color from
yellow to brown to blackMelanin is produced by melanocytesFound
mainly in the stratum basaleAccumulates in membrane-bound granules
called melanosomes
Epidermis - MelaninThe amount of melanin in the epidermis
results from genetics and sunlight exposureFreckles and moles are
seen in areas where melanin is concentrated
DERMIS
DermisDermis your hideTwo layers:Papillary Layer (upper
region)Reticular Layer (lower region)
Dermis Papillary LayerDermal PapillaeIndent epidermis
aboveCreate fingerprintsCapillary loopsNourish epidermisPain and
touch receptorsPain free nerve endingsTouch Meissners
corpuscles
Dermis Reticular LayerBlood vesselsSweat and oil glandsDeep
pressure receptors Pacinian corpusclesContain phagocytes that
prevent bacteria from reaching deeper tissues
DermisHeavy in collagen and elastic fibersAs age increases,
these fibers decrease as do fat cells and skin sagsAbundantly
supplied with bloodSkin reds and warms with high body tempRich
nerve supply
SKIN COLOR
Skin ColorThree pigments contribute to skin color:1. the amount
and kind of melanin2. the amount of carotene in the stratum corneum
and subcutaneous tissue3. the amount of hemoglobin in the dermal
blood vessels
Skin ColorPeople with a lot of melanin have brown-toned
skinPeople with less melanin have fair-toned skin
Skin ColorThe hemoglobin in the dermal blood supply shows
through the transparent cell layers aboveThis gives skin a rosy
glow
Skin ColorEmotions also influence skin color, and many
alterations in skin color signal disease:1. Redness (erythema)
reddened skinBlushing, fever, hypertension, inflammation,
allergy
Skin Color2. Pallor (blanching)Emotional stress (fear,
anger)Anemia, hypotension, impaired blood flow3. Jaundice
(yellowing)Liver/Gallbladder disorders excess of bilirubin in the
blood
Skin Color4. Bruises (black and blue coloring)Show where blood
has escaped circulation and has clotted in tissue spacesHematomasAn
unusual tendency to bruising may signify a deficiency of vitamin C
or hemophilia
Skin appendages
Skin appendagesSkin appendages: skin-associated structures that
serve a particular functionFunctions include sensation,
contractility, lubrication and heat loss
Skin AppendagesSkin appendages include cutaneous glands, hair
and hair follicles, nailsArise from the epidermisPlay a role in
homeostasis
Cutaneous GlandsExocrine glandsRelease secretions to the skin
surface via ductsTwo groups:Sebaceous glandsSweat glandsFormed in
the stratum basale and push into the deeper layers of the
dermis
Sebaceous GlandsOil glandsFound all over skin except palms and
solesSebum: the product of sebaceous glandsLubricate skinKills
bacteriaMost with ducts empty into hair folliclesIncrease
production during puberty
Sweat GlandsAlso called sudoriferous glands Widely distributed
across the skinTwo types:1. eccrineOpen via duct to pore on
skinProduce sweatImportant in heat regulation2. apocrineUsually
larger than eccrine glandsDucts empty into hair folliclesActivated
during pain and stress
Sweat Glands
Sweat and its FunctionComposition:Mostly waterSome metabolic
wastes (ammonia, urea, etc.)Fatty acids and proteins (apocrine
only)Function:Helps dissipate excess heatExcretes waste
productsAcidity decreases bacterial growthOdor is from associated
bacteria
Hair and Hair Follicles Produced by hair bulbFormed by
well-nourished stratum basale cells in the matrix (growth
zone)Consists of hard, keratinized epithelial cellsMelanocytes
provide pigment for hair color
Hair and Hair Follicles
Hair AnatomyCentral medullaCortex surrounds medullaCuticle on
outside of cortexMost heavily keratinized
Hair structuresHair follicleDermal and epidermal sheath surround
hair rootArrector piliSmooth muscleCause hair to stand upGoosebumps
(piloerection)Sebaceous glandLubricates hairSweat gland
Hair functionWarmthLimited in humansProtectionTouch
senseNon-verbal communication (eyebrows and eyelashes)
Human Body Hair TypesAccording to forensic scientists there are
six types of hair on the human body:HeadEyebrow and eyelashBeard
and moustacheBody hair (Auxilairy)PubicArmpit
NailsScale-like modifications of the epidermisHighly
keratinizedStratum basale extends beneath the nail bedResponsible
for growthLack of pigment makes them colorless
Nail Structures Free EdgeBodyRoot of NailEponychium: proximal
nail fold that projects into the nail body
SKIN HOMEOSTATIC IMBALANCES
InfectionsAthletes FootMedically known as tinea pedisCaused by a
fungal infectionThrives in warm, moist areasContagious by
contact
InfectionsBoils and CarbunclesInflammation of hair follicles and
sebaceous glandsCaused by bacterial infection
InfectionsCold soresCaused by the Herpes Simplex VirusCan remain
dormant for extended periods of time
InfectionsImpetigoCaused by bacterial infection (staph)Highly
contagiousCommon in elementary children
AllergiesContact dermatitisExposure to substance causes an
allergic reactionEx. poison ivy
AllergiesPsoriasisChronic, autoimmune conditionCan be
disfiguringAttacks are often triggered by trauma, infection, stress
or hormonal changes
BURNS
BurnsBurn: tissue damage and cell death caused by heat,
electricity, UV radiation (sunburns) or chemicals
BurnsImmediate Associated Dangers:
1. Dehydration
2. Electrolyte Imbalance
3. Circulatory Shock
Burns Rule of NinesWay of determining the extent of burns (how
much of the body is burned)
Body is divided into 11 areas for quick estimationEach area
represents about 9% of the body(last 1% is the area surrounding the
gentials)
Burns Rule of Nines
Burns - SeverityFirst-Degree
Second Degree
Third-Degree
Burns - Severity
1st degree burnsOnly the epidermis is damaged (superficial)Skin
is red and swollenNo blisteringMinimal painUsually heals in a week
or less
Cool, cover loosely, over the counter pain medications
1st degree burns
2nd degree burnsEpidermis and upper dermis are damaged (partial
thickness)Skin is redBlisters that sometimes breakSevere painTakes
up to a month to heal
Cool, cover loosely, over the counter pain medsBe cautious of
infections
2nd degree burns
3rd degree burnsDestroy entire skin layer (full thickness)Skin
is gray-white or black; may appear waxy of charredMinimal pain at
first due to nerve damage
Partial or complete skin grafts, biomask, amnionPossible system
shock and cardiac or respiratory arrestExtended healing time
3rd degree burns
3rd degree burn treatment
Critical BurnsBurns are considered critical if:Over 25% of the
body has 2nd degree burnsOver 10% of the body has 3rd degree
burnsThere are third degree burns of the face, hands or feet
Critical BurnsFacial burnsParticularly dangerousPossibility of
burns in respiratory passageCan cause swelling and
suffocationJointsScar tissue can limit mobility
SKIN CANCER
Skin CancerCancer abnormal cell massTwo typesBenignDoes not
spread (encapsulated)MalignantMetastasized (moves) to other parts
of the bodyMost common type of cancer
Skin Cancer TypesBasal Cell CarcinomaLeast malignantMost common
typeArises from stratum basale
Skin Cancer TypesSquamous Cell CarcinomaArises from stratum
spinosumMetastasizes to lymph nodesEarly removal allows for a good
chance of a cure
Skin Cancer TypesMalignant MelanomaMost deadly type of skin
cancerCancer of melanocytesMetastasizes rapidly to lymph and blood
vesselsDetection uses ABCD rule
ABCD Rules
ABCD RulesA = AsymmetryTwo sides of pigmented mole do not
match
B = Border IrregularityBorders of mole are not smooth
ABCD RulesC = ColorDifferent colors in pigmented area
D = DiameterSpot is larger than 6mm in diameter
ABCD Rules
