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5 . The Integumentary System. Skin (Integument). Consists of three major regions Epidermis—superficial region Dermis—middle region Hypodermis (superficial fascia)—deepest region Subcutaneous layer deep to skin (not technically part of skin) Mostly adipose tissue. Hair shaft. - PowerPoint PPT PresentationTRANSCRIPT
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PowerPoint® Lecture Slides prepared by Janice Meeking, Mount Royal College
C H A P T E R
Copyright © 2010 Pearson Education, Inc.
5 The Integumentary System
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Skin (Integument)
• Consists of three major regions
1. Epidermis—superficial region
2. Dermis—middle region
3. Hypodermis (superficial fascia)—deepest region
• Subcutaneous layer deep to skin (not technically part of skin)
• Mostly adipose tissue
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Copyright © 2010 Pearson Education, Inc. Figure 5.1
Epidermis
Hair shaft
Dermis Reticularlayer
Papillarylayer
Hypodermis(superficial fascia)
Dermal papillae
Pore
Subpapillaryvascular plexus
Appendagesof skin • Eccrine sweat gland• Arrector pili muscle• Sebaceous (oil) gland• Hair follicle• Hair rootNervous structures
• Sensory nerve fiber• Pacinian corpuscle• Hair follicle receptor (root hair plexus)
Cutaneous vascularplexus
Adipose tissue
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Epidermis
• Keratinized stratified squamous epithelium
• Cells of epidermis• Keratinocytes—produce fibrous protein keratin
• Melanocytes
• Produce pigment melanin
• Dendritic (Langerhans) cells—macrophages that help activate immune system
• Tactile (Merkel) cells—touch receptors
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Copyright © 2010 Pearson Education, Inc. Figure 5.2a
Dermis
Stratum corneumMost superficial layer; 20–30 layers of deadcells represented only by flat membranoussacs filled with keratin. Glycolipids inextracellular space.Stratum granulosumThree to five layers of flattened cells,organelles deteriorating; cytoplasm full oflamellated granules (release lipids) andkeratohyaline granules.Stratum spinosumSeveral layers of keratinocytes unified bydesmosomes. Cells contain thick bundles ofintermediate filaments made of pre-keratin.Stratum basaleDeepest epidermal layer; one row of activelymitotic stem cells; some newly formed cellsbecome part of the more superficial layers.See occasional melanocytes and epidermaldendritic cells.
(a)
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Layers of the Epidermis: Stratum Basale (Basal Layer)• Deepest epidermal layer firmly attached to the
dermis
• Single row of stem cells
• Also called stratum germinativum: cells undergo rapid division
• Journey from basal layer to surface• Takes 25–45 days
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Layers of the Epidermis: Stratum Spinosum (Prickly Layer)• Cells contain a weblike system of intermediate
prekeratin filaments
• Abundant melanin granules and dendritic cells
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Layers of the Epidermis: Stratum Granulosum (Granular Layer)• Thin; three to five layers of dying cells
• cells flatten
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Layers of the Epidermis: Stratum Lucidum (Clear Layer)• In thick skin
• A few rows of flat, dead keratinocytes
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Layers of the Epidermis: Stratum Corneum
• 20–30 rows of dead, flat, keratinized membranous sacs• Three-quarters of the epidermal thickness• Functions• Protects from abrasion and penetration• Waterproofs• Barrier against biological, chemical, and
physical assaults
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Copyright © 2010 Pearson Education, Inc. Figure 5.2b
MelanocyteMelanin granule
Tactile(Merkel) cell
Sensorynerve ending Epidermal
dendritic cell
Dermis
KeratinocytesStratum corneumMost superficial layer; 20–30 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space.Stratum granulosumThree to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules.Stratum spinosumSeveral layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin.Stratum basaleDeepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and epidermal dendritic cells. Desmosomes
(b)
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Dermis
• Strong, flexible connective tissue
• Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells
• Two layers: • Papillary
• Reticular
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Copyright © 2010 Pearson Education, Inc. Figure 5.1
Epidermis
Hair shaft
Dermis Reticularlayer
Papillarylayer
Hypodermis(superficial fascia)
Dermal papillae
Pore
Subpapillaryvascular plexus
Appendagesof skin • Eccrine sweat gland• Arrector pili muscle• Sebaceous (oil) gland• Hair follicle• Hair rootNervous structures
• Sensory nerve fiber• Pacinian corpuscle• Hair follicle receptor (root hair plexus)
Cutaneous vascularplexus
Adipose tissue
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Layers of the Dermis: Papillary Layer
• Papillary layer• Areolar connective tissue with collagen and
elastic fibers and blood vessels
• Dermal papillae contain:
• Capillary loops
• Meissner’s corpuscles
• Free nerve endings
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Layers of the Dermis: Reticular Layer
• Reticular layer• ~80% of the thickness of dermis
• Collagen fibers provide strength and resiliency
• Elastic fibers provide stretch-recoil properties
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Skin Markings: Friction Ridges
• Epidermal ridges lie atop deeper dermal papillary ridges to form friction ridges of fingerprints
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Copyright © 2010 Pearson Education, Inc. Figure 5.4a
Friction ridges
(a)
Openings ofsweat gland ducts
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Skin Markings: Cleavage Lines
• Collagen fibers arranged in bundles form cleavage (tension) lines
• Incisions made parallel to cleavage lines heal more readily
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Copyright © 2010 Pearson Education, Inc. Figure 5.4b
(b)
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Skin Color
• Three pigments contribute to skin color:1. Melanin• Yellow to reddish-brown to black,
responsible for dark skin colors• Produced in melanocytes; migrates to
keratinocytes where it forms “pigment shields” for nuclei
• Freckles and pigmented moles• Local accumulations of melanin
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Skin Color
2. Carotene
• Yellow to orange, most obvious in the palms and soles
3. Hemoglobin
• Responsible for the pinkish hue of skin
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Appendages of the Skin
• Derivatives of the epidermis• Sweat glands
• Oil glands
• Hairs and hair follicles
• Nails
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Sweat Glands
• Two main types of sweat (sudoriferous) glands
1. Eccrine (merocrine) sweat glands—abundant on palms, soles, and forehead
• Sweat: 99% water, NaCl, vitamin C, antibodies, dermcidin, metabolic wastes
• Ducts connect to pores
• Function in thermoregulation
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Copyright © 2010 Pearson Education, Inc. Figure 5.5b
(b) Photomicrograph of a sectioned eccrine gland (220x)
Secretory cells
Dermal connectivetissue
DuctSebaceousgland
Sweat pore
Eccrinegland
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Sweat Glands
2. Apocrine sweat glands—confined to axillary and anogenital areas• Sebum: sweat + fatty substances and proteins• Ducts connect to hair follicles• Functional from puberty onward
• Specialized apocrine glands• Ceruminous glands—in external ear canal; secrete
cerumen (wax)• Mammary glands
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Sebaceous (Oil) Glands
•Widely distributed
• Most develop from hair follicles
• Become active at puberty
• Sebum• Oily holocrine secretion
• Bactericidal
• Softens hair and skin
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Copyright © 2010 Pearson Education, Inc. Figure 5.5a
(a) Photomicrograph of a sectioned sebaceous gland (220x)
Sebaceousgland ductHair inhair follicleSecretory cells
Dermalconnectivetissue
Sebaceousgland
Sweatpore
Eccrinegland
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Hair
• Functions• Alerting the body to presence of insects on the
skin
• Guarding the scalp against physical trauma, heat loss, and sunlight
• Distribution• Entire surface except palms, soles, lips,
nipples, and portions of external genitalia
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Hair
• Consists of dead keratinized cells
• Contains hard keratin; more durable than soft keratin of skin
• Hair pigments: melanins (yellow, rust brown, black)• Gray/white hair: decreased melanin
production, increased air bubbles in shaft
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Copyright © 2010 Pearson Education, Inc. Figure 5.6a
Hair shaft
ArrectorpiliSebaceousglandHair root
Hair bulb
(a) Diagram of a cross section of a hair within its follicle
• Connective tissue root sheath• Glassy membrane• External epithelial root sheath• Internal epithelial root sheath
Follicle wall
• Cuticle• Cortex• Medulla
Hair
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(b) Photomicrograph of a cross section of a hair and hair follicle (250x)
• Connective tissue root sheath
Follicle wall
• Cuticle
• Glassy membrane
• Cortex• Medulla
• Internal epithelial root sheath
• External epithelial root sheath
Hair
Hair shaft
ArrectorpiliSebaceousglandHair root Hair bulb
Figure 5.6b
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Hair Follicle
• Extends from the epidermal surface into dermis
• Two-layered wall: outer connective tissue root sheath, inner epithelial root sheath
• Hair bulb: expanded deep end
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Hair Follicle
• Hair follicle receptor (root hair plexus) • Sensory nerve endings around each hair bulb
• Stimulated by bending a hair
• Arrector pili• Smooth muscle attached to follicle
• Responsible for “goose bumps”
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Copyright © 2010 Pearson Education, Inc. Figure 5.6c
Hair shaft
ArrectorpiliSebaceousglandHair root Hair bulb
(c) Diagram of a longitudinal view of the expanded hairbulb of the follicle, which encloses the matrix
• Internal epithelial root sheath• External epithelial root sheath
• Connective tissue root sheathFollicle wall
Hair matrix
MelanocyteHair papilla
Subcutaneous adipose tissue
• Medulla• Cortex• Cuticle
• Glassy membrane
Hair root
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(d) Photomicrograph of longitudinal view of the hair bulb in the follicle (160x)
Follicle wall
Hair matrixHair papilla
Subcutaneousadipose tissue
Hair root
• Connective tissue root sheath• Glassy membrane• External epithelial root sheath• Internal epithelial root sheath
• Cuticle• Cortex• Medulla
Hair shaft
ArrectorpiliSebaceousglandHair root
Hair bulb
Figure 5.6d
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Types of Hair
• Vellus—pale, fine body hair of children and adult females
• Terminal—coarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males)
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Hair Thinning and Baldness
• Alopecia—hair thinning in both sexes after age 40
• True (frank) baldness • Genetically determined and sex-influenced
condition
• Male pattern baldness is caused by follicular response to DHT
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Structure of a Nail
• Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes
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Copyright © 2010 Pearson Education, Inc. Figure 5.7
Lateralnail fold
Lunule
Nailmatrix
Root of nail
Proximalnail fold
Hyponychium
Nail bed
Phalanx (bone of fingertip)
Eponychium(cuticle)
Bodyof nail
Free edgeof nail
(a)
(b)
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Functions of the Integumentary System
1. Protection—three types of barriers• Chemical
• Low pH secretions (acid mantle) and defensins retard bacterial activity
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Functions of the Integumentary System
• Physical/mechanical barriers• Keratin and glycolipids block most water and
water- soluble substances• Limited penetration of skin by lipid-soluble
substances, plant oleoresins (e.g., poison ivy), organic solvents, salts of heavy metals, some drugs
• Biological barriers• Dendritic cells, macrophages, and DNA
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Functions of the Integumentary System
2. Body temperature regulation• ~500 ml/day of routine insensible
perspiration (at normal body temperature)
• At elevated temperature, dilation of dermal vessels and increased sweat gland activity (sensible perspirations) cool the body
3. Cutaneous sensations• Temperature, touch, and pain
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Functions of the Integumentary System
4. Metabolic functions• Synthesis of vitamin D precursor and
collagenase• Chemical conversion of carcinogens and
some hormones
5. Blood reservoir—up to 5% of body’s blood volume
6. Excretion—nitrogenous wastes and salt in sweat
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Skin Cancer
• Most skin tumors are benign (do not metastasize)
• Risk factors• Overexposure to UV radiation
• Frequent irritation of the skin
• Some skin lotions contain enzymes in liposomes that can fix damaged DNA
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Skin Cancer
• Three major types:• Basal cell carcinoma
• Least malignant, most common
• Squamous cell carcinoma
• Second most common
• Melanoma
• Most dangerous
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Basal Cell Carcinoma
• Stratum basale cells proliferate and slowly invade dermis and hypodermis
• Cured by surgical excision in 99% of cases
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Copyright © 2010 Pearson Education, Inc. Figure 5.8a
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Squamous Cell Carcinoma
• Involves keratinocytes of stratum spinosum
• Most common on scalp, ears, lower lip, and hands
• Good prognosis if treated by radiation therapy or removed surgically
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Copyright © 2010 Pearson Education, Inc. Figure 5.8b
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Melanoma
• Involves melanocytes
• Highly metastatic and resistant to chemotherapy
• Treated by wide surgical excision accompanied by immunotherapy
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Melanoma
• Characteristics (ABCD rule)
A: Asymmetry; the two sides of the pigmented area do not match
B: Border exhibits indentations
C: Color is black, brown, tan, and sometimes red or blue
D: Diameter is larger than 6 mm (size of a pencil eraser)
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Copyright © 2010 Pearson Education, Inc. Figure 5.8c
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Burns
• Heat, electricity, radiation, certain chemicals
Burn
(tissue damage, denatured protein, cell death)
• Immediate threat:• Dehydration and electrolyte imbalance, leading
to renal shutdown and circulatory shock
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Rule of Nines
• Used to estimate the volume of fluid loss from burns
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Copyright © 2010 Pearson Education, Inc. Figure 5.9
Anterior and posteriorhead and neck, 9%
41/2%41/2%
Anterior and posteriorupper limbs, 18%
Anterior and posteriorlower limbs, 36%
100%
Totals
Anterior and posteriortrunk, 36%
Anteriortrunk,18%
9% 9%(Perineum, 1%)
41/2%
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Partial-Thickness Burns
• First degree• Epidermal damage only
• Localized redness, edema (swelling), and pain
• Second degree• Epidermal and upper dermal damage
• Blisters appear
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Copyright © 2010 Pearson Education, Inc. Figure 5.10a
(a) Skin bearing partialthickness burn (1st and 2nd degree burns)
1st degreeburn
2nd degreeburn
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Full-Thickness Burns
• Third degree• Entire thickness of skin damaged
• Gray-white, cherry red, or black
• No initial edema or pain (nerve endings destroyed)
• Skin grafting usually necessary
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Copyright © 2010 Pearson Education, Inc. Figure 5.10b
(b) Skin bearing fullthickness burn(3rd degree burn)
3rddegreeburn
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Severity of Burns
• Critical if:• >25% of the body has second-degree burns
• >10% of the body has third-degree burns
• Face, hands, or feet bear third-degree burns
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Developmental Aspects: Fetal
• Ectoderm epidermis
• Mesoderm dermis and hypodermis
• Lanugo coat: covering of delicate hairs in 5th and 6th month
• Vernix caseosa: sebaceous gland secretion; protects skin of fetus
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Developmental Aspects: Adolescent to Adult• Sebaceous gland activity increases
• Effects of cumulative environmental assaults show after age 30
• Scaling and dermatitis become more common
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Developmental Aspects: Old Age
• Epidermal replacement slows, skin becomes thin, dry, and itchy
• Subcutaneous fat and elasticity decrease, leading to cold intolerance and wrinkles
• Increased risk of cancer due to decreased numbers of melanocytes and dendritic cells