Skin and Body Membranes

Body MembranesFunction of body membranes

Cover body surfacesLine body cavitiesForm protective sheets around organs

Classification of Body MembranesEpithelial membranes

Cutaneous membranesMucous membranesSerous membranes

Connective tissue membranesSynovial membranes

Cutaneous MembraneCutaneous membrane = skin

Dry membraneOutermost protective boundary

Superficial epidermis is composed of keratinized stratified squamous epithelium

Underlying dermis is mostly dense connective tissue

Cutaneous Membranes

Figure 4.1a

Mucous Membranes

Surface epithelium type depends on siteStratified squamous epithelium (mouth,

esophagus)Simple columnar epithelium (rest of digestive

tract)Underlying loose connective tissue (lamina

propria)Lines all body cavities that open to the

exterior body surfaceOften adapted for absorption or secretion

Mucous Membranes

Figure 4.1b

Serous MembranesSurface is a layer of simple squamous

epitheliumUnderlying layer is a thin layer of areolar

connective tissueLines open body cavities that are closed to

the exterior of the bodySerous membranes occur in pairs

separated by serous fluidVisceral layer covers the outside of the organParietal layer lines a portion of the wall of

ventral body cavity

Serous Membranes

Figure 4.1d

Serous MembranesSpecific serous membranes

PeritoneumAbdominal cavity

PleuraAround the lungs

PericardiumAround the heart

Serous Membranes

Figure 4.1c

Connective Tissue MembraneSynovial membrane

Connective tissue onlyLines fibrous capsules surrounding jointsSecretes a lubricating fluid

Connective Tissue Membrane

Figure 4.2

Integumentary SystemSkin (cutaneous membrane)Skin derivatives

Sweat glandsOil glandsHairNails

Skin Functions

Table 4.1 (1 of 2)

Skin Functions

Table 4.1 (2 of 2)

Skin StructureEpidermis—outer layer

Stratified squamous epitheliumOften keratinized (hardened by keratin)

DermisDense connective tissue

Skin Structure

Figure 4.3

Skin StructureSubcutaneous tissue (hypodermis) is deep

to dermisNot part of the skinAnchors skin to underlying organsComposed mostly of adipose tissue

Layers of the EpidermisStratum basale (stratum germinativum)

Deepest layer of epidermisLies next to dermisCells undergoing mitosisDaughter cells are pushed upward to become

the more superficial layersStratum spinosumStratum granulosum

Layers of the EpidermisStratum lucidum

Formed from dead cells of the deeper strataOccurs only in thick, hairless skin of the

palms of hands and soles of feetStratum corneum

Outermost layer of epidermisShingle-like dead cells are filled with keratin

(protective protein prevents water loss from skin)

Layers of the EpidermisSummary of layers from deepest to most

superficialStratum basaleStratum spinosumStratum granulosumStratum lucidum (thick, hairless skin only)Stratum corneum

MelaninPigment (melanin) produced by

melanocytesMelanocytes are mostly in the stratum

basaleColor 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 loopsOther house pain receptors and touch receptors

Reticular layer (deepest skin layer)Blood vesselsSweat and oil glandsDeep pressure receptors

DermisOverall dermis structure

Collagen and elastic fibers located throughout the dermisCollagen fibers give skin its toughnessElastic fibers give skin elasticity

Blood vessels play a role in body temperature regulation

Skin Structure

Figure 4.4

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

Skin AppendagesCutaneous glands are all exocrine glands

Sebaceous glandsSweat glands

HairHair folliclesNails

Appendages of the SkinSebaceous glands

Produce oilLubricant for skinPrevents brittle hairKills bacteria

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

Glands are activated at puberty

Appendages of the Skin

Figure 4.6a

Appendages of the SkinSweat glands

Produce sweat Widely distributed in skinTwo types

EccrineOpen via duct to pore on skin surface

ApocrineDucts empty into hair follicles

Appendages of the Skin

Figure 4.6b

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

Appendages of the SkinHair

Produced by hair follicleConsists of hard keratinized epithelial cellsMelanocytes provide pigment for hair color

Appendages of the Skin

Figure 4.7c

Appendages of the SkinHair anatomy

Central medullaCortex surrounds

medullaCuticle on outside

of cortexMost heavily

keratinized

Figure 4.7b

Appendages of the SkinAssociated hair structures

Hair follicleDermal and epidermal sheath surround hair root

Arrector pili muscle Smooth musclePulls hairs upright when cold or frightened

Sebaceous glandSweat gland

Appendages of the Skin

Figure 4.7a

Appendages of the Skin

Figure 4.8

Appendages of the SkinNails

Scale-like modifications of the epidermisHeavily keratinized

Stratum basale extends beneath the nail bedResponsible for growth

Lack of pigment makes them colorless

Appendages of the SkinNail structures

Free edgeBody is the visible attached portionRoot of nail embedded in skinCuticle is the proximal nail fold that projects

onto the nail body

Appendages of the Skin

Figure 4.9

Skin Homeostatic ImbalancesInfections

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

Boils and carbunclesCaused by bacterial infection

Cold soresCaused by virus

Skin Homeostatic ImbalancesInfections and allergies

Contact dermatitisExposures cause allergic reaction

ImpetigoCaused by bacterial infection

PsoriasisCause is unknownTriggered by trauma, infection, stress

Skin Homeostatic Imbalances

Figure 4.10

Skin Homeostatic ImbalancesBurns

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

Associated dangersDehydrationElectrolyte imbalanceCirculatory shock

Rule of NinesWay to determine the extent of burnsBody is divided into 11 areas for quick

estimationEach area represents about 9% of total

body surface area

Rule of Nines

Figure 4.11a

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 layerBurn is gray-white or black

Severity of Burns

Figure 4.11b

Critical BurnsBurns are considered critical if

Over 25% of body has second-degree burnsOver 10% of the body has third-degree burnsThere are third-degree burns of the face,

hands, or feet

Skin CancerCancer—abnormal cell massClassified two ways

BenignDoes not spread (encapsulated)

MalignantMetastasized (moves) to other parts of the body

Skin cancer is the most common type of cancer

Skin Cancer TypesBasal cell carcinoma

Least malignantMost common typeArises from stratum basale

Skin Cancer Types

Figure 4.12a

Skin Cancer TypesSquamous cell carcinoma

Metastasizes to lymph nodes if not removedEarly removal allows a good chance of cureBelieved to be sun-inducedArises from stratum spinosum

Skin Cancer Types

Figure 4.12b

Skin Cancer TypesMalignant melanoma

Most deadly of skin cancersCancer of melanocytesMetastasizes rapidly to lymph and blood

vesselsDetection uses ABCD rule

Skin Cancer Types

Figure 4.12c

ABCD RuleA = Asymmetry

Two sides of pigmented mole do not matchB = Border irregularity

Borders of mole are not smoothC = Color

Different colors in pigmented areaD = Diameter

Spot is larger then 6 mm in diameter