integumentary.ppt - Integumentary System Dr Ancrum Chapter 5 Skin(Integument Consists of two distinct regions Epidermis\u2014superficial region Epithelial

integumentary.ppt - Integumentary System Dr Ancrum Chapter...

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Unformatted text preview: Integumentary System Dr. Ancrum Chapter 5 Skin (Integument) Consists of two distinct regions Epidermis—superficial region Epithelial tissue Dermis—underlies epidermis Mostly fibrous connective tissue Hypodermis (superficial fascia) Subcutaneous layer deep to skin Not part of skin but shares some functions Mostly adipose tissue that absorbs shock & insulates Anchors skin to underlying structures – mostly muscles Hair shaft Dermal papillae Epidermis Subpapillary plexus Papillary layer Sweat pore Appendages of skin Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Dermis Reticular layer Hypodermis (subcutaneous tissue; not part of skin) Nervous structures Sensory nerve fiber with free nerve endings Lamellar corpuscle Hair follicle receptor (root hair plexus) Cutaneous plexus Adipose tissue Epidermis Keratinized stratified squamous epithelium Four or five distinct layers Stratum Stratum Stratum Stratum Stratum basale spinosum granulosum lucidum (only in thick skin) corneum Four cell types Keratinocytes Melanocytes Dendritic (langerhans) cells Tactile (merkel) cells Stratum corneum Most superficial layer; 20–30 layers of dead cells, essentially flat membranous sacs filled with keratin. Glycolipids in extracellular space. Stratum granulosum Typically five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellar granules (release lipids) and keratohyaline granules. Dermis Stratum spinosum Several layers of keratinocytes unified by desmosomes. Cells contain thick bundles of intermediate filaments made of pre-keratin. Stratum basale Deepest epidermal layer; one row of actively mitotic stem cells; some newly formed cells become part of the more superficial layers. See occasional melanocytes and dendritic cells. Cells of the Epidermis Keratinocytes Produce fibrous protein keratin Most cells of epidermis Tightly connected by desmosomes Melanocytes 10–25% of cells in deepest epidermis Produce pigment melanin Protect apical surface of keratinocyte nucleus from UV damage Dendritic (langerhans) cells Macrophages – key activators of immune system Tactile (merkel) cells Sensory touch receptors Cellular extension of melanocyte Epidermis Pigment granules Golgi apparatus Melanocyte nucleus Basement membrane Dermis (b) Layers of the Epidermis: Stratum Corneum (Horny Layer) • 20–30 rows of dead, flat, anucleate keratinized membranous sacs • Three-quarters of epidermal thickness • Though dead, its cells have functions • Protect deeper cells from environment and water loss • Protect from abrasion and penetration • Barrier against biological, chemical, and physical assaults Stratum Lucidum (Clear Layer) • Only in thick skin • Thin, translucent band superficial to the stratum granulosum • A few rows of flat, dead keratinocytes Stratum Granulosum (Granular Layer) Thin - four to six cell layers Cell appearance changes Cells flatten Nuclei and organelles disintegrate Keratinization begins Cells accumulate keratohyaline granules Help form keratin in upper layers Cell accumulate lamellar granules Their water-resistant glycolipid slows water loss Cells above this layer die Too far from dermal capillaries Stratum Spinosum (Prickly Layer) • Several layers thick • Cells contain web-like system of intermediate prekeratin filaments attached to desmosomes • Abundant melanosomes and dendritic cells Layers of the Epidermis: Stratum Basale (Basal Layer) Deepest epidermal layer Also called stratum germinativum Firmly attached to dermis Single row of stem cells Actively mitotic Produces two daughter cells One cell journeys from basal layer to surface Takes 25–45 days Dies as moves toward surface One cell remains in stratum basale as stem cell Melanocytes compose 10 – 25% of this layer Cell Differentiation in Epidermis • Cells change from stratum basale to stratum corneum • Accomplished by specialized form of apoptosis • • • • • Controlled cellular suicide Nucleus and organelles break down Plasma membrane thickens Allows cells to slough off as dandruff and dander Shed ~ 50,000 cells every minute Epidermal Layers Dermis Strong, flexible connective tissue Cells Fibroblasts, macrophages, and occasionally mast cells and white blood cells Fibers in matrix bind body together "Hide" used to make leather Contains nerve fibers; blood and lymphatic vessels Contains epidermal hair follicles; oil and sweat glands Two layers Papillary Reticular Hair shaft Dermal papillae Epidermis Subpapillary plexus Papillary layer Sweat pore Appendages of skin Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Dermis Reticular layer Hypodermis (subcutaneous tissue; not part of skin) Nervous structures Sensory nerve fiber with free nerve endings Lamellar corpuscle Hair follicle receptor (root hair plexus) Cutaneous plexus Adipose tissue Layers of the Dermis: Papillary Layer • Areolar connective tissue with collagen and elastic fibers and blood vessels • Loose tissue • Phagocytes can patrol for microorganisms • Dermal papillae • Superficial peglike projections Dermal Papillae Most contain capillary loops Some contain Meissner's corpuscles (touch receptors) Some contain free nerve endings (pain receptors) In thick skin lie atop dermal ridges that cause epidermal ridges Collectively ridges called friction ridges Enhance gripping ability Contribute to sense of touch Pattern is fingerprints Openings of Friction sweat gland ducts ridges Friction ridges of fingertip (SEM 12x) Layers of the Dermis: Reticular Layer ~80% of dermal thickness Dense fibrous connective tissue Elastic fibers provide stretch-recoil properties Collagen fibers • • • Provide strength and resiliency Bind water Cleavage lines because most collagen fibers parallel to skin surface Externally invisible Important to surgeons Incisions parallel to cleavage lines gap less and heal more readily Cleavage lines in the reticular dermis Skin Markings • Flexure lines • Dermal folds at or near joints • Dermis tightly secured to deeper structures so skin cannot slide easily for joint movement causing deep creases. • Visible on hands, wrists, fingers, soles, toes Flexure lines on digit Flexure lines on the palm Flexure lines of the hand Other Skin Markings • Striae • Silvery-white scars • "Stretch marks" • Extreme stretching causes dermal tears • Blister • From acute, short-term trauma • Fluid-filled pocket that separates epidermal and dermal layers Skin Color • Three pigments contribute to skin color • Melanin • Only pigment made in skin • Carotene • Hemoglobin Melanin Two forms Reddish-yellow to brownish-black Color differences due to amount and form Produced in melanocytes Same relative number in all people Migrates to keratinocytes to form "pigment shields" for nuclei Freckles and pigmented moles Local accumulations of melanin Sun exposure stimulates melanin production Sunspots (tinea versicolor) are fungal infection; not related to melanin • Carotene Carotene and Hemoglobin • Yellow to orange pigment • Most obvious in palms and soles • Accumulates in stratum corneum and hypodermis • Can be converted to vitamin A for vision and epidermal health • Hemoglobin • Pinkish hue of fair skin Skin Color in Diagnosis Cyanosis Blue skin color - low oxygenation of hemoglobin Erythema (redness) Fever, hypertension, inflammation, allergy Pallor (blanching)- Pale Anemia, low blood pressure, fear, anger Jaundice (yellow cast) Liver disorder Icterus- jaundice in the eyes Bronzing Inadequate steroid hormones in Addison's disease Bruises Clotted blood beneath skin Appendages of the Skin • Derivatives of the epidermis • • • • Hairs and hair follicles Nails Sweat glands Sebaceous (oil) glands Hair Dead keratinized cells of hard keratin More durable than soft keratin of skin Not in palms, soles, lips, nipples, portions of external genitalia Functions include Warn off insects on skin Physical trauma Heat loss Sunlight Hair pigments Melanins (yellow, rust, brown, black); trichosiderin in red hair Gray/white hair: decreased melanin production, increased air bubbles in shaft Hair Follicles Extend from epidermal surface to dermis Two-layered wall - part dermis, part epidermis Hair bulb Expanded deep end Hair follicle receptor (root hair plexus) Sensory nerve endings - touch receptors Hair matrix Actively dividing area Arrector pili Smooth muscle attached to follicle Responsible for "goose bumps" Hair papilla Dermal tissue - blood supply Figure 5.5a Skin appendages: Structure of a hair and hair follicle. Follicle wall • Peripheral connective tissue (fibrous) sheath • Glassy membrane • Epithelial root sheath • External root sheath • Internal root sheath Hair shaft Hair • Cuticle • Cortex • Medulla Diagram of a cross section of a hair within its follicle Arrector pili Sebaceous gland Hair root Hair bulb Figure 5.5b Skin appendages: Structure of a hair and hair follicle. Follicle wall • Peripheral connective tissue (fibrous) sheath • Glassy membrane • Epithelial root sheath • External root sheath • Internal root sheath Hair • Cuticle • Cortex • Medulla Photomicrograph of a cross section of a hair and hair follicle (100x) Figure 5.5c Skin appendages: Structure of a hair and hair follicle. Hair shaft Arrector pili Sebaceous gland Hair root Hair bulb Follicle wall • Peripheral connective tissue (fibrous) sheath • Glassy membrane • Epithelial root sheath • External root sheath • Internal root sheath Hair root • Cuticle • Cortex • Medulla Hair matrix Hair papilla Melanocyte Subcutaneous adipose tissue Diagram of a longitudinal view of the expanded hair bulb of the follicle, which encloses the matrix Figure 5.5d Skin appendages: Structure of a hair and hair follicle. Follicle wall • Peripheral connective tissue (fibrous) sheath • Glassy membrane • Epithelial root sheath • External root sheath • Internal root sheath Hair root • Cuticle • Cortex • Medulla Hair matrix Hair papilla Subcutaneous adipose tissue Photomicrograph of longitudinal view of the hair bulb in the follicle (160x) Types and Growth of Hair Vellus hair Pale, fine body hair of children and adult females Terminal hair Coarse, long hair of eyebrows, scalp At puberty Appear in axillary and pubic regions of both sexes Face and neck of males Nutrition and hormones affect hair growth Follicles cycle between active and regressive phases Average 2.25 mm growth per week Lose 90 scalp hairs daily Hair Thinning and Baldness • Alopecia • Hair thinning in both sexes after a age 40 • True (frank) baldness • Genetically determined and sex-influenced condition • Male pattern baldness caused by follicular response to DHT (dihydrotestosterone) • Treatments • Minoxidil (rogaine) and finasteride (propecia) Nails • Scalelike modifications of epidermis • Protective cover for distal, dorsal surface of fingers and toes • Contain hard keratin • Nail matrix • Nail growth Figure 5.6 Skin appendages: Structure of a nail. Lunule Lateral nail fold Free edge Body Eponychium Root of nail of nail of nail (cuticle) Proximal Nail nail fold matrix Hyponychium Nail bed Phalanx (bone of fingertip) Sweat Glands • Also called sudoriferous glands • All skin surfaces except nipples and parts of external genitalia • ~3 million per person • Two main types • Eccrine (merocrine) sweat glands • Apocrine sweat glands • Contain myoepithelial cells • Contract upon nervous system stimulation to force sweat into ducts Eccrine Sweat Glands • Most numerous • Abundant on palms, soles, and forehead • Ducts connect to pores • Function in thermoregulation • Regulated by sympathetic nervous system • Their secretion is sweat • 99% water, salts, vitamin c, antibodies, dermcidin (microbe-killing peptide), metabolic wastes Sebaceous gland Sweat pore Eccrine gland Duct Dermal connective tissue Secretory cells Photomicrograph of a sectioned eccrine gland (140x) Apocrine Sweat Glands Confined to axillary and anogenital areas Sweat + fatty substances + proteins Viscous; milky or yellowish Odorless until bacterial interaction body odor Larger than eccrine sweat glands Ducts usually empty into hair follicles Begin functioning at puberty Function unknown but may act as sexual scent gland Modified apocrine glands Ceruminous glands—lining of external ear canal; secrete cerumen (earwax) Mammary glands – secrete milk Sebaceous (Oil) Glands Widely distributed • Not in thick skin of palms and soles Most develop from hair follicles and secrete into hair follicles Relatively inactive until puberty • Stimulated by hormones, especially androgens Secrete sebum • Oily holocrine secretion • Bactericidal • Softens hair and skin Merocrine Apocrine Holocrine Figure 5.7a Photomicrograph of a sectioned sebaceous gland (90x). Sebaceous gland Dermal connective Hair in tissue hair follicle Sebaceous gland duct Sweat pore Eccrine gland Secretory cells Photomicrograph of a sectioned sebaceous gland (90x) Functions of the Integumentary System • Protection • Body temperature regulation • Cutaneous sensation • Metabolic functions • Blood reservoir • Excretion Protection • Three types of barriers • Chemical barriers • Physical barriers • Biological barriers Chemical Barriers • Skin secretions • Low pH slows bacterial multiplication • Sebum and defensins kill bacteria • Melanin • Defense against UV radiation damage Physical Barriers Flat, dead cells of stratum corneum surrounded by lipids Keratin and glycolipids block most water and water- soluble substances Limited penetration of skin Lipid-soluble substances Plant oleoresins (e.g., Poison ivy) Organic solvents Salts of heavy metals Some drugs Drug agents Biological Barriers • Biological barriers • Dendritic cells of epidermis • Present foreign antigens to white blood cells • Macrophages of dermis • Present foreign antigens to white blood cells • DNA • Its electrons absorb UV radiation • Radiation converted to heat Functions of the Integumentary System • Body temperature regulation • If body temperature normal, ~500 ml/day of routine insensible perspiration (if environmental temperature below 87-89° F) • If body temperature rises, dilation of dermal vessels and increased sweat gland activity (sensible perspiration) cool the body • Cold external environment • Dermal blood vessels constrict • Skin temperature drops to slow passive heat loss Functions of the Integumentary System Cutaneous sensations Cutaneous sensory receptors – part of nervous system – detect temperature, touch, and pain Metabolic functions Synthesis of vitamin D precursor and collagenase Chemical conversion of carcinogens and activate some hormones Blood reservoir—up to 5% of body's blood volume Excretion—nitrogenous wastes and salt in sweat Skin Cancer • Most skin tumors are benign (not cancerous) and do not metastasize (spread) • Risk factors • Overexposure to UV radiation • Frequent irritation of skin • Three major types of skin cancer • Basal cell carcinoma • Squamous cell carcinoma • Melanoma Basal Cell Carcinoma • Least malignant; most common • Stratum basale cells proliferate and slowly invade dermis and hypodermis • Cured by surgical excision in 99% of cases Squamous Cell Carcinoma • Second most common type • Involves keratinocytes of stratum spinosum • Usually scaly reddened papule on scalp, ears, lower lip, and hands • Does metastasize • Good prognosis if treated by radiation therapy or removed surgically Melanoma Cancer of melanocytes Most dangerous Highly metastatic and resistant to chemotherapy Treated by wide surgical excision accompanied by immunotherapy Key to survival is early detection – ABCD rule A: asymmetry; the two sides of the pigmented area do not match B: border irregularity; exhibits indentations C: color; contains several (black, brown, tan, sometimes red or blue) D: diameter; larger than 6 mm (size of pencil eraser) Figure 5.8 Photographs of skin cancers. Basal cell carcinoma Squamous cell carcinoma Melanoma Burns Tissue damage caused by heat, electricity, radiation, certain chemicals • Denatures proteins • Kills cells Immediate threat: • Dehydration and electrolyte imbalance Leads to renal shutdown and circulatory shock To evaluate burns • Rule of nines • Used to estimate volume of fluid loss Figure 5.9 Estimating the extent and severity of burns using the rule of nines. Totals 41/2% Anterior and posterior head and neck, 9% Anterior and posterior upper limbs, 18% 41/2% 1 Anterior 4 /2% trunk, 18% 9% 9% Anterior and posterior trunk, 36% (Perineum, 1%) Anterior and posterior lower limbs, 36% 100% Burns Classified by Severity Partial-thickness burns First degree Epidermal damage only Localized redness(erythema), edema (swelling), and pain Second degree Epidermal and upper dermal damage Blisters appear Full-thickness burns Third degree Entire thickness of skin involved Skin gray-white, cherry red, or blackened Not painful (nerve endings destroyed) or swollen Skin grafting usually necessary 1st Degree Burn 2nd Degree burns 3rd Degree Burn 4th Degree Severity and Treatment of Burns • Critical if • >25% of body has second-degree burns • >10% of body has third-degree burns • Face, hands, or feet bear third-degree burns • Treatment includes • • • • Debridement (removal) of burned skin Antibiotics Temporary covering Skin grafts Developmental Aspects Fetal Ectoderm epidermis; Mesoderm dermis and hypodermis Lanugo coat: delicate hairs in 5th and 6th month Vernix caseosa: sebaceous gland secretion; protects skin of fetus Infancy to adulthood Skin thickens; accumulates more subcutaneous fat Sweat and sebaceous gland activity increases Effects of cumulative environmental assaults show after age 30 Scaling and dermatitis become more common Vernix caseosa Developmental Aspects Aging skin • Epidermal replacement slows, skin becomes thin, dry and itchy (decreased sebaceous gland activity) • Subcutaneous fat and elasticity decrease, leading to cold intolerance and wrinkles • Increased risk of cancer due to decreased numbers of melanocytes and dendritic cells • Hair thinning To delay • UV protection, good nutrition, lots of fluids, good hygiene The End ...
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