essentials of human anatomy skin and body membranes

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Essentials of Human AnatomyEssentials of Human Anatomy Skin and Body Membranes

Chapter 4Dr Fadel Naim

Ass. Prof. Faculty of MedicineIUG

Body Membranes• Thin tissue layers that cover surfaces, line cavities, Thin tissue layers that cover surfaces, line cavities,

and divide spaces or organs and divide spaces or organs • Epithelial membranes are most common typeEpithelial membranes are most common type

– Cutaneous membrane (skin)Cutaneous membrane (skin)• Primary organ of integumentary systemPrimary organ of integumentary system• One of the most important organsOne of the most important organs• Composes approximately 16% of body weightComposes approximately 16% of body weight

– Serous membrane (serosa)Serous membrane (serosa)• Parietal membranes—line closed body cavitiesParietal membranes—line closed body cavities• Visceral membranes—cover visceral organsVisceral membranes—cover visceral organs• Pleura—surrounds a lung and lines the thoracic cavityPleura—surrounds a lung and lines the thoracic cavity• Peritoneum—covers the abdominal viscera and lines the Peritoneum—covers the abdominal viscera and lines the

abdominal cavityabdominal cavity

Body Membranes

• Mucous membrane (mucosa)Mucous membrane (mucosa)– Lines and protects organs that open to the exterior of the bodyLines and protects organs that open to the exterior of the body– Found lining ducts and passageways of respiratory, digestive, other Found lining ducts and passageways of respiratory, digestive, other

tractstracts– Lamina propria—fibrous connective tissue underlying mucous Lamina propria—fibrous connective tissue underlying mucous

epitheliumepithelium– Mucus is made up mostly of water and mucins—proteoglycans that Mucus is made up mostly of water and mucins—proteoglycans that

form a double-layer protection against environmental microbesform a double-layer protection against environmental microbes

• Connective tissue membranesConnective tissue membranes– Do not contain epithelial componentsDo not contain epithelial components– Synovial membranes—line the spaces between bone in jointsSynovial membranes—line the spaces between bone in joints– Have smooth and slick membranes that secrete synovial fluidHave smooth and slick membranes that secrete synovial fluid– Help reduce friction between opposing surfaces in a moveable jointHelp reduce friction between opposing surfaces in a moveable joint– Synovial membranes also line bursaeSynovial membranes also line bursae

Ventral Body Cavity Membranes

• Parietal serosa lines internal body walls• Visceral serosa covers the internal organs• Serous fluid separates the serosae

Serous Membranes

• Skin (integument) is body’s largest organSkin (integument) is body’s largest organ• Approximately 1.6 to 1.9 mApproximately 1.6 to 1.9 m22 in average-sized adult in average-sized adult• Integumentary system describes the skin Integumentary system describes the skin

and its appendages—the hair, nails, and and its appendages—the hair, nails, and skin glandsskin glands

• Thin and thick skinThin and thick skin– ““Thin skin”—covers most of body surface Thin skin”—covers most of body surface

(1 to 3 mm thick)(1 to 3 mm thick)– ““Thick skin”—soles and palms Thick skin”—soles and palms

(4 to 5 mm thick)(4 to 5 mm thick)

Anatomy of Skin

Functions of Skin

Function of Integumentary SystemA. Regulation of Body TemperatureB. Protection from Dehydration and InfectionC. Respond to Temperature, Pressure, PainD. Excretion of Water, Salts, Urea (nitrogenous waste)E. Synthesis Vitamin D (essential for Ca + P absorption)

F. First Defensive Barrier of Immune Response

Functions of the Skin

• ProtectionProtection– Physical barrier to microorganismsPhysical barrier to microorganisms– Barrier to chemical hazardsBarrier to chemical hazards– Reduces potential for mechanical traumaReduces potential for mechanical trauma– Prevents dehydrationPrevents dehydration– Protects (via melanin) excess UV exposureProtects (via melanin) excess UV exposure

Functions of the Skin• SensationSensation

– Skin acts as a sophisticated sense organSkin acts as a sophisticated sense organ– Somatic sensory receptors detect stimuli that Somatic sensory receptors detect stimuli that

permit us to detect pressure, touch, permit us to detect pressure, touch, temperature, pain, and other general temperature, pain, and other general sensationssensations

Functions of the Skin• FlexibilityFlexibility

– Skin is supple and elastic, thus permitting Skin is supple and elastic, thus permitting change in body contours without injurychange in body contours without injury

• ExcretionExcretion– WaterWater– Urea/ammonia/uric acidUrea/ammonia/uric acid

Functions of the Skin• Hormone (Vitamin D) productionHormone (Vitamin D) production

– Exposure of skin to UV light converts Exposure of skin to UV light converts 7-dehydrocholesterol to cholecalciferol— 7-dehydrocholesterol to cholecalciferol— a precursor to vitamin Da precursor to vitamin D

– Blood transports precursor to liver and Blood transports precursor to liver and kidneys, where vitamin D is producedkidneys, where vitamin D is produced

– Process and end result fulfill the necessary Process and end result fulfill the necessary steps required for vitamin D to be classified as steps required for vitamin D to be classified as a hormonea hormone


• ImmunityImmunity– Phagocytic cells destroy bacteriaPhagocytic cells destroy bacteria– Langerhans cells trigger helpful immune Langerhans cells trigger helpful immune

reaction working with “helper T cells”reaction working with “helper T cells”


– Heat lossHeat loss• approximately 80% of heat loss occurs through the approximately 80% of heat loss occurs through the

skin; remaining 20% occurs through the mucosa of skin; remaining 20% occurs through the mucosa of the respiratory, digestive, and urinary tractsthe respiratory, digestive, and urinary tracts

Layers of Skin

• Epidermis• Dermis• Subcutaneous layer• beneath dermis • not part of skin

Epidermis

• Lacks blood vessels• Keratinized• Thickest on palms and soles (0.8-1.4mm)• Melanocytes provide melanin• Rests on basement membrane• Stratified squamous

Epidermis

Layers of Epidermis• stratum corneum• stratum lucidum• stratum granulosum• stratum spinosum• stratum basale

Structure of the Skin• EpidermisEpidermis

– Cell typesCell types• Keratinocytes—Keratinocytes— constitute constitute

over 90% of cells present; over 90% of cells present; principal structural element of principal structural element of the outer skinthe outer skin

• Melanocytes—Melanocytes— pigment- pigment-producing cells (5% of the producing cells (5% of the total); contribute to skin color; total); contribute to skin color; filter ultraviolet lightfilter ultraviolet light

• Langerhans cells—Langerhans cells— dendritic dendritic (branched) antigen-presenting (branched) antigen-presenting cells (APCs), they play a role cells (APCs), they play a role in immune responsein immune response

Structure of the Skin• EpidermisEpidermis

– Cell layersCell layers• Stratum germinativum (growth layer)—Stratum germinativum (growth layer)—

describes the stratum spinosum and stratum describes the stratum spinosum and stratum basale togetherbasale together

– Stratum basale (base layer)—Stratum basale (base layer)—single layer of single layer of columnar cells; only these cells undergo mitosis, then columnar cells; only these cells undergo mitosis, then migrate through the other layers until they migrate through the other layers until they are shed are shed

– Stratum spinosum (spiny layer)—Stratum spinosum (spiny layer)—cells arranged in 8 cells arranged in 8 to 10 layers with desmosomes that pull cells into spiny to 10 layers with desmosomes that pull cells into spiny shapes; cells rich in RNAshapes; cells rich in RNA

Structure of the Skin– Cell layersCell layers

• Stratum granulosum (granular layer)—Stratum granulosum (granular layer)—cells cells arranged in two to four layers and filled with arranged in two to four layers and filled with keratohyalin granules; contain high levels of keratohyalin granules; contain high levels of lysosomal enzymes lysosomal enzymes

• Stratum lucidum (clear layer)—Stratum lucidum (clear layer)—cells filled with cells filled with keratin precursor called keratin precursor called eleidin;eleidin; absent in thin skin absent in thin skin

• Stratum corneum (horny layer)—most superficial Stratum corneum (horny layer)—most superficial layer; dead cells filled with keratin (barrier area)layer; dead cells filled with keratin (barrier area)

Structure of the Skin– Epidermal growth and repairEpidermal growth and repair

• Turnover or regeneration time refers to time required for Turnover or regeneration time refers to time required for epidermal cells to form in the stratum basale and migrate epidermal cells to form in the stratum basale and migrate to the skin surface—about 35 daysto the skin surface—about 35 days

• Shortened turnover time will increase the thickness of Shortened turnover time will increase the thickness of the stratum corneum and result in callus formationthe stratum corneum and result in callus formation

• Normally 10% to 12% of all cells in stratum basale enter Normally 10% to 12% of all cells in stratum basale enter mitosis dailymitosis daily

• Each group of 8 to 10 basal cells in mitosis with their Each group of 8 to 10 basal cells in mitosis with their vertical columns of migrating keratinocytes is called an vertical columns of migrating keratinocytes is called an epidermal proliferating unitepidermal proliferating unit, or , or EPUEPU

Structure of the Skin

• Dermal-epidermal junctionDermal-epidermal junction– A definite basement membrane, A definite basement membrane,

specialized fibrous elements, and a specialized fibrous elements, and a polysaccharide gel serve to “glue” the polysaccharide gel serve to “glue” the epidermis to the dermis belowepidermis to the dermis below

– The junction serves as a partial barrier to The junction serves as a partial barrier to the passage of some cells and large the passage of some cells and large moleculesmolecules

Structure of the Skin• DermisDermis

– Sometimes called “true skin”—much thicker Sometimes called “true skin”—much thicker than the epidermis and lies beneath itthan the epidermis and lies beneath it

– Gives strength to the skinGives strength to the skin– Serves as a reservoir area for storage of Serves as a reservoir area for storage of

water and electrolyteswater and electrolytes

Dermis

• Contains dermal papillae• Binds epidermis to underlying tissues• Irregular dense connective tissue

• On average 1.0-2.0mm thick

• Muscle cells• Nerve cell processes• Specialized sensory receptors• Blood vessels• Hair follicles• Glands

Structure of the Skin• DermisDermis

– Contains various structures:Contains various structures:• Arrector pili muscles and hair follicles Arrector pili muscles and hair follicles • Sensory receptors Sensory receptors • Sweat and sebaceous glandsSweat and sebaceous glands• Blood vesselsBlood vessels

– Rich vascular supply plays a critical role in Rich vascular supply plays a critical role in temperature regulationtemperature regulation

Structure of the Skin• Dermis Dermis

– Layers of dermis:Layers of dermis:• Papillary layer—Papillary layer— composed of dermal papillae that composed of dermal papillae that

project into the epidermis; contains fine project into the epidermis; contains fine collagenous and elastic fibers; contains the dermal-collagenous and elastic fibers; contains the dermal-epidermal junction; forms a unique pattern that epidermal junction; forms a unique pattern that gives individual fingerprintsgives individual fingerprints

• Reticular layer—Reticular layer— contains dense, interlacing white contains dense, interlacing white collagenous fibers and elastic fibers to make the collagenous fibers and elastic fibers to make the skin tough yet stretchable; when processed from skin tough yet stretchable; when processed from animal skin, produces leatheranimal skin, produces leather

Lines of Cleavage

• Tension lines in the skin identify the predominant orientation of collagen fiber bundles.

• Clinically and surgically significant because cuts can result in slow healing and increased scarring.

Structure of the Skin

• Dermis remains a scarDermis remains a scar• Dermal growth and repairDermal growth and repair

• The dermis does not continually shed and regenerate itself The dermis does not continually shed and regenerate itself as does the epidermisas does the epidermis

• During wound healing, the fibroblasts begin forming an During wound healing, the fibroblasts begin forming an unusually dense mass of new connective fibers; if not unusually dense mass of new connective fibers; if not replaced by normal tissue, this mass by the collagenous replaced by normal tissue, this mass by the collagenous fibers of the reticular layer of the dermis; also called Langer’s fibers of the reticular layer of the dermis; also called Langer’s lineslines

Subcutaneous Layer

• hypodermis

• loose connective tissue

• adipose tissue

• insulates

• major blood vessels

Structure of the Skin• Hypodermis Hypodermis

– Also called subcutaneous layer or superficial Also called subcutaneous layer or superficial fasciafascia

– Deep to the dermis, forming connection Deep to the dermis, forming connection between the skin and other structuresbetween the skin and other structures

– Not part of the skinNot part of the skin

Skin Color

Genetic Factors• varying amounts of melanin• varying size of melanin granules• albinos lack melanin

Environmental Factors• sunlight• UV light from sunlamps• X rays• darkens melanin

Physiological Factors• dilation of dermal blood vessels• constriction of dermal blood vessels• accumulation of carotene• jaundice

Skin Color– Melanin

• Basic determinant of skin color is quantity, type, and distribution of Basic determinant of skin color is quantity, type, and distribution of melaninmelanin

– Beta carotene • (group of yellowish pigments from food) can also contribute to skin (group of yellowish pigments from food) can also contribute to skin

colorcolor– Hemoglobin

• color changes also occur as a result of changes in blood flow color changes also occur as a result of changes in blood flow – Redder skin color when blood flow to skin increasesRedder skin color when blood flow to skin increases– Cyanosis—bluish color caused by darkening of hemoglobin when Cyanosis—bluish color caused by darkening of hemoglobin when

it loses oxygen and gains carbon dioxide (Figure 6-9)it loses oxygen and gains carbon dioxide (Figure 6-9)– Bruising can cause a rainbow of different colors to appear in the Bruising can cause a rainbow of different colors to appear in the

skin skin – Other pigments

• from cosmetics, tattoos, and bile pigments in jaundice cosmetics, tattoos, and bile pigments in jaundice

Basis of Skin Color• The color of skin and mucous membranes can provide The color of skin and mucous membranes can provide

clues for diagnosing certain problems, such asclues for diagnosing certain problems, such as

– JaundiceJaundice• yellowish color to skin and whites of eyesyellowish color to skin and whites of eyes• buildup of yellow bilirubin in blood from liver diseasebuildup of yellow bilirubin in blood from liver disease

– CyanosisCyanosis• bluish color to nail beds and skinbluish color to nail beds and skin• hemoglobin depleted of oxygen looks purple-bluehemoglobin depleted of oxygen looks purple-blue

– ErythemaErythema• redness of skin due to enlargement of capillaries in dermisredness of skin due to enlargement of capillaries in dermis• during inflammation, infection, allergy or burnsduring inflammation, infection, allergy or burns

Sebaceous glandsSebaceous glands• Secrete sebum—oily substance that keeps hair and skin Secrete sebum—oily substance that keeps hair and skin

soft and pliant; prevents excessive water loss from the soft and pliant; prevents excessive water loss from the skinskin

• usually associated with hair follicles• Lipid components have antifungal activityLipid components have antifungal activity• Simple, branched glandsSimple, branched glands• Found in dermis except in palms and solesFound in dermis except in palms and soles• Secretion increases in adolescence; may lead to Secretion increases in adolescence; may lead to

formation of pimples and blackheadsformation of pimples and blackheads

Skin glands

Sweat Glands

• Widespread in skin

• Originates in deeper dermis Or hypodermis

• Eccrine glands

• Apocrine glands

• Ceruminous glands

• Mammary glands

• Eccrine glandsEccrine glands

–Most numerous sweat glands; quite smallMost numerous sweat glands; quite small–Distributed over total body surface with Distributed over total body surface with

exception of a few small areasexception of a few small areas–Simple, coiled, tubular glandsSimple, coiled, tubular glands–Function throughout lifeFunction throughout life–Secrete perspiration or sweat; eliminate Secrete perspiration or sweat; eliminate

wastes; and help maintain a constant core wastes; and help maintain a constant core temperaturetemperature

Sweat glands

• Apocrine glandsApocrine glands

–Located deep in subcutaneous layerLocated deep in subcutaneous layer–Limited distribution—axilla, areola of breast, Limited distribution—axilla, areola of breast,

and around anusand around anus–Large (often more than 5 mm in diameter)Large (often more than 5 mm in diameter)–Simple, branched, tubular glandsSimple, branched, tubular glands–Begin to function at pubertyBegin to function at puberty–Secretion shows cyclic changes in female Secretion shows cyclic changes in female

with menstrual cyclewith menstrual cycle

Sweat glands

Ceruminous glandsCeruminous glands

• Modified apocrine sweat glandsModified apocrine sweat glands• Simple, coiled, tubular glandsSimple, coiled, tubular glands• Empty contents into external ear canal alone or with Empty contents into external ear canal alone or with

sebaceous glandssebaceous glands• Mixed secretions of sebaceous and ceruminous glands Mixed secretions of sebaceous and ceruminous glands

called cerumen (wax)called cerumen (wax)• Function of cerumen to protect area from dehydration; Function of cerumen to protect area from dehydration;

excess secretion can cause blockage of ear canal and excess secretion can cause blockage of ear canal and loss of hearingloss of hearing

Sweat glands

Hair

• Distribution—over entire body except Distribution—over entire body except palms of hands and soles of feet and a palms of hands and soles of feet and a few other small areasfew other small areas

• Fine and soft hair coat present before birth called Fine and soft hair coat present before birth called lanugolanugo

• Coarse pubic and axillary hair that develops at Coarse pubic and axillary hair that develops at puberty called puberty called terminal hairterminal hair

Functions of Hair • Protection • Heat retention • Prevents the loss of conducted heat from the

scalp to the surrounding air • Facial expression• Sensory reception • Visual identification • Chemical signal dispersal

Hair Follicles

• Epidermal cells• Tube-like depression• Extends into dermis• Hair root• Hair shaft• Hair papilla• Dead epidermal cells• Melanin• Arrector pili muscle

A. Shaft - projects above surface of epidermis

1. medulla - polyhedral cells with eleidin2. cortex - elongated cells with/out

pigment3. cuticle - outermost layer, like shingles

on roof B. Root - below epidermis, penetrates

into the dermis C. Hair Follicle - at the base a a single

hair 1. external root sheath - basale and

spinosum extension2. internal root sheath - internal hair

cell layers3. bulb - base of hair cell4. papilla - in the bulb, provides

nourishment for hair5. matrix - origin of new hair cellsD. arrector pili - smooth muscle, cause

hair to risenerve bundle responds to touch

E. hair root plexuses

• ColorColor– result of different amounts, distribution, types of melanin in result of different amounts, distribution, types of melanin in

cortex of haircortex of hair

• GrowthGrowth– hair growth and rest periods alternate; hair on head averages 5 hair growth and rest periods alternate; hair on head averages 5

inches of growth per yearinches of growth per year

• Sebaceous glandsSebaceous glands– attach to and secrete sebum attach to and secrete sebum

(skin oil) into follicle(skin oil) into follicle

• Male pattern baldness results from combination of genetic Male pattern baldness results from combination of genetic tendency and male sex hormonestendency and male sex hormones

Appearance of hair

Hair Thinning and Baldness

• Alopecia – hair thinning in both sexes• True, or frank, baldness

– Genetically determined and sex-influenced condition

Consist of epidermal cells Consist of epidermal cells converted to hard keratinconverted to hard keratin

– Nail body—visible part of Nail body—visible part of each naileach nail

– Root—part of nail in groove Root—part of nail in groove hidden by fold of skin, the hidden by fold of skin, the cuticlecuticle

– Lunula—moon-shaped Lunula—moon-shaped white area nearest rootwhite area nearest root

Nails

• Nail bed—layer of epithelium under nail bodyNail bed—layer of epithelium under nail body– contains abundant blood vesselscontains abundant blood vessels

• Appears pink under translucent nailsAppears pink under translucent nails• Growth—nails grow by mitosis of cells in stratum germinativum Growth—nails grow by mitosis of cells in stratum germinativum

beneath the lunula; average growth about 0.5 mm per week, or beneath the lunula; average growth about 0.5 mm per week, or slightly over 1 inch per yearslightly over 1 inch per year

Burns• Tissue damage from excessive heat, electricity, radioactivity, Tissue damage from excessive heat, electricity, radioactivity,

or corrosive chemicals that destroys (denatures) proteins in or corrosive chemicals that destroys (denatures) proteins in the exposed cells is called athe exposed cells is called a burn. burn.

• Generally, the systemic effects of a burn are a greater threat Generally, the systemic effects of a burn are a greater threat to life than are the local effects.to life than are the local effects.

• The seriousness of a burn is determined by The seriousness of a burn is determined by – Its depthIts depth– ExtentExtent– Area involvedArea involved– The person’s age and general health. The person’s age and general health.

• When the burn area exceeds 70%, over half of the victims dieWhen the burn area exceeds 70%, over half of the victims die

Burns

• Destruction of proteins of the skinDestruction of proteins of the skin– chemicals, electricity, heatchemicals, electricity, heat

• Problems that resultProblems that result– shock due to water, plasma and plasma shock due to water, plasma and plasma

protein lossprotein loss– circulatory & kidney problems from loss of circulatory & kidney problems from loss of

plasmaplasma– bacterial infectionbacterial infection

Types of Burns• First-degreeFirst-degree

– only epidermis (sunburn)only epidermis (sunburn)

Types of Burns• Second-degree burn Second-degree burn

– destroys entire epidermis & part of dermis destroys entire epidermis & part of dermis – fluid-filled blisters separate epidermis & dermisfluid-filled blisters separate epidermis & dermis– epidermal derivatives are not damagedepidermal derivatives are not damaged– heals without grafting in 3 to 4 weeks & may scarheals without grafting in 3 to 4 weeks & may scar

Types of Burns• Third-degree or full-thicknessThird-degree or full-thickness

– destroy epidermis, dermis & epidermal derivativesdestroy epidermis, dermis & epidermal derivatives– damaged area is numb due to loss of sensory nervesdamaged area is numb due to loss of sensory nerves

Rule of Nines

Cycle of Life: Skin

• ChildrenChildren– Skin is smooth, unwrinkled, and characterized Skin is smooth, unwrinkled, and characterized

by elasticity and flexibilityby elasticity and flexibility– Few sweat glandsFew sweat glands– Rapid healingRapid healing

Cycle of Life: Skin

• AdultsAdults– Development and activation of sebaceous Development and activation of sebaceous

and sweat glandsand sweat glands– Increased sweat productionIncreased sweat production

• Body odorBody odor– Increased sebum productionIncreased sebum production

• AcneAcne

Aging• Skin repair processes take longer due to

reduced number and activity of stem cells. • Skin forms wrinkles and becomes less resilient. • Skin’s immune responsiveness is diminished.• Skin becomes drier due to decreased

sebaceous gland activity.• Altered skin and hair pigmentation.

Cycle of Life: Skin

Aging• Sweat production diminishes. • Blood supply to the dermis is reduced

leading to impaired thermoregulation. • Hair thinning and loss. • Integumentary production of vitamin D3

diminishes. • Development of skin cancers.

Cycle of Life: Skin

Skin and Aging Process

Skin Cancer

• The most common type of cancer. • The greatest risk factor is exposure to UV

rays of the sun. • The highest incidence is in people who

have had severe sunburns, especially as children.

Skin Cancer

• Most skin tumors are benign and do not metastasize

• The three major types of skin cancer are:– Basal cell carcinoma– Squamous cell carcinoma– Melanoma

Basal Cell Carcinoma• Least malignant and most common skin cancer• Stratum basale cells proliferate and invade the

dermis and hypodermis• Slow growing and do not often metastasize• Can be cured by surgical excision in 99% of the

cases

Squamous Cell Carcinoma• Arises from keratinocytes of stratum spinosum• Arise most often on scalp, ears, and lower lip• Grows rapidly and metastasizes if not removed• Prognosis is good if treated by radiation therapy

or removed surgically

MelanomaCancer of melanocytes is the most dangerous type

of skin cancer because it is:– Highly metastatic– Resistant to chemotherapy

MelanomaMelanomas have these characteristics (ABCD rule)

– A: Asymmetry; the two sides of the pigmented area do not match

– B: Border is irregular and exhibits indentations– C: Color (pigmented area) is black, brown, tan, and

sometimes red or blue– D: Diameter is larger than 6 mm (size of a pencil

eraser)

Melanoma• Treated by wide surgical excision

accompanied by immunotherapy• Chance of survival is poor if the lesion is

over 4 mm thick

THE END

essentials of human anatomy skin and body membranes

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