1 essentials of human anatomy essentials of human anatomy skin dr fadel naim ass. prof. faculty of...
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Essentials of Human AnatomyEssentials of Human Anatomy
Skin
Dr Fadel NaimAss. Prof. Faculty of Medicine
IUG
Slide 2
• 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
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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
Slide 5
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
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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
Slide 7
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
Slide 8
Functions of the Skin• 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”
Slide 9
Functions of the Skin– 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
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Structure of the Skin• EpidermisEpidermis
– Cell typesCell types• Keratinocytes—Keratinocytes— constitute over 90% of cells present; constitute over 90% of cells present;
principal structural element of the outer skinprincipal structural element of the outer skin• Melanocytes—Melanocytes— pigment-producing cells (5% of the total); pigment-producing cells (5% of the total);
contribute to skin color; filter ultraviolet lightcontribute to skin color; filter ultraviolet light• Langerhans cells—Langerhans cells— dendritic (branched) antigen-presenting dendritic (branched) antigen-presenting
cells (APCs), they play a role in immune responsecells (APCs), they play a role in immune response
Epidermis
Layers of Epidermis• stratum corneum• stratum lucidum• stratum granulosum• stratum spinosum• stratum basale
Slide 14
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
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Structure of the Skin– Cell layersCell layers
• Stratum granulosum (granular layer)—Stratum granulosum (granular layer)—cells cells arranged in 2-4 layers and filled with keratohyalin arranged in 2-4 layers and filled with keratohyalin granules; contain high levels of lysosomal granules; contain high levels of lysosomal enzymes 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)Stratum corneum (horny layer)—most superficial —most superficial layer; dead cells filled with keratin (barrier area)layer; dead cells filled with keratin (barrier area)
Slide 16
Structure of the Skin– Epidermal growth and repairEpidermal growth and repair
• Turnover or regeneration time Turnover or regeneration time refers to time refers to time required for epidermal cells to form in the stratum required for epidermal cells to form in the stratum basale and migrate to the skin surfacebasale and migrate to the skin surface—about 35 —about 35 daysdays
• Shortened turnover time Shortened turnover time will increase the thickness will increase the thickness of the stratum corneum and result in of the stratum corneum and result in callus formationcallus formation
• Normally Normally 10% to 12% 10% to 12% of all cells in stratum basale of all cells in stratum basale enter mitosis dailyenter mitosis daily
• Each group of Each group of 8 to 10 basal cells in mitosis with 8 to 10 basal cells in mitosis with their vertical columns of migrating keratinocytes their vertical columns of migrating keratinocytes is called an is called an epidermal proliferating unitepidermal proliferating unit, or , or EPUEPU
Slide 17
Structure of the Skin
• Dermal-epidermal junctionDermal-epidermal junction– A definite A definite basement membrane, basement membrane,
specialized fibrous elementsspecialized fibrous elements, and a , and a polysaccharide gel serve to polysaccharide gel serve to “glue” the “glue” the epidermis to the dermis belowepidermis to the dermis below
– The junction serves as The junction serves as a partial barrier a partial barrier to to the passage of some cells and large the passage of some cells and large moleculesmolecules
Slide 18
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
Slide 20
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
Slide 21
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 epidermisproject into the epidermis; contains fine ; contains fine collagenous and elastic fiberscollagenous and elastic fibers; contains the ; contains the dermal-epidermal junctiondermal-epidermal junction; forms a unique ; forms a unique pattern that gives pattern that gives individual fingerprintsindividual fingerprints
• Reticular layer—Reticular layer— contains contains dense, interlacing dense, interlacing white collagenous fibers and elastic fiberswhite collagenous fibers and elastic fibers to to make the skin make the skin tough yet stretchabletough yet stretchable; when ; when processed from animal skin, produces processed from animal skin, produces leatherleather
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.
Slide 24
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
Subcutaneous Layer
• hypodermis
• loose connective tissue
• adipose tissue
• insulates
• major blood vessels
Slide 26
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
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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
Slide 29
Skin Color– Melanin
• Basic determinant of skin color is quantity, type, and distribution of melaninBasic determinant of skin color is quantity, type, and distribution of melanin– Beta carotene
• (group of yellowish pigments from food) can also contribute to skin color(group of yellowish pigments from food) can also contribute to skin color– 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 it Cyanosis—bluish color caused by darkening of hemoglobin when it
loses oxygen and gains carbon dioxide (Figure 6-9)loses oxygen and gains carbon dioxide (Figure 6-9)– Bruising can cause a rainbow of different colors to appear in the skin Bruising can cause a rainbow of different colors to appear in the skin
– Other pigments• from cosmetics, tattoos, and bile pigments in jaundice cosmetics, tattoos, and bile pigments in jaundice
Slide 30
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
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Sebaceous glandsSebaceous glands• Secrete sebum—oily substance that keeps hair Secrete sebum—oily substance that keeps hair
and skin soft and pliant; prevents excessive water and skin soft and pliant; prevents excessive water loss from the skinloss from the skin
• 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
Slide 33
• 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
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• 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
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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
Slide 36
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
Slide 40
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• 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
Slide 45
– Consist of epidermal cells converted to hard Consist of epidermal cells converted to hard keratinkeratin
– Nail body—visible part of each nailNail body—visible part of each nail– Root—part of nail in groove hidden by fold of Root—part of nail in groove hidden by fold of
skin, the cuticleskin, the cuticle– Lunula—moon-shaped white area nearest Lunula—moon-shaped white area nearest
rootroot
Nails
Slide 46
• 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
Slide 47
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
Slide 48
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
Slide 49
Types of Burns• First-degreeFirst-degree
– only epidermis (sunburn)only epidermis (sunburn)
Slide 50
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
Slide 51
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
Slide 53
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
Slide 54
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
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