The Integumentary System Skin (Integument) F Consists of three major regions 1. Epidermissuperficial region 2. Dermismiddle region 3. Hypodermis (superficial fascia)deepest region F Subcutaneous layer deep to skin (not technically part of skin) F Mostly adipose tissue F Consists of three major regions 1. Epidermissuperficial region 2. Dermismiddle region 3. Hypodermis (superficial fascia)deepest region F Subcutaneous layer deep to skin (not technically part of skin) F Mostly adipose tissue Figure 5.1 Epidermis Hair shaft Dermis Reticular layer Papillary layer Hypodermis (superficial fascia) Dermal papillae Pore Subpapillary vascular plexus Appendages of skin Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Nervous structures Sensory nerve fiber Pacinian corpuscle Hair follicle receptor (root hair plexus) Cutaneous vascular plexus Adipose tissue Epidermis F Keratinized stratified squamous epithelium F Cells of epidermis F Keratinocytesproduce fibrous protein keratin F Melanocytes F 1025% of cells in lower epidermis F Produce pigment melanin F Epidermal dendritic (Langerhans) cells macrophages that help activate immune system F Tactile (Merkel) cellstouch receptors F Keratinized stratified squamous epithelium F Cells of epidermis F Keratinocytesproduce fibrous protein keratin F Melanocytes F 1025% of cells in lower epidermis F Produce pigment melanin F Epidermal dendritic (Langerhans) cells macrophages that help activate immune system F Tactile (Merkel) cellstouch receptors Figure 5.2a Dermis Stratum corneum Most superficial layer; 2030 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space. Stratum granulosum Three to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules. 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 epidermal dendritic cells. (a) Layers of the Epidermis: Stratum Basale (Basal Layer) F Deepest epidermal layer firmly attached to the dermis F Single row of stem cells F Also called stratum germinativum: cells undergo rapid division F Journey from basal layer to surface F Takes 2545 days F Deepest epidermal layer firmly attached to the dermis F Single row of stem cells F Also called stratum germinativum: cells undergo rapid division F Journey from basal layer to surface F Takes 2545 days Layers of the Epidermis: Stratum Spinosum (Prickly Layer) F Cells contain a weblike system of intermediate prekeratin filaments attached to desmosomes F Abundant melanin granules and dendritic cells F Cells contain a weblike system of intermediate prekeratin filaments attached to desmosomes F Abundant melanin granules and dendritic cells Layers of the Epidermis: Stratum Granulosum (Granular Layer) F Thin; three to five cell layers in which the cells flatten F Keratohyaline and lamellated granules accumulate F Thin; three to five cell layers in which the cells flatten F Keratohyaline and lamellated granules accumulate Layers of the Epidermis: Stratum Lucidum (Clear Layer) F In thick skin (soles of the feet & palms of the hands) F Thin, transparent band superficial to the stratum granulosum F A few rows of flat, dead keratinocytes F Lies below the Stratum Corneum F In thick skin (soles of the feet & palms of the hands) F Thin, transparent band superficial to the stratum granulosum F A few rows of flat, dead keratinocytes F Lies below the Stratum Corneum Layers of the Epidermis: Stratum Corneum (Horny Layer) F 2030 rows of dead, flat, keratinized membranous sacs F Three-quarters of the epidermal thickness F Functions F Protects from abrasion and penetration F Waterproofs F Barrier against biological, chemical, and physical assaults F 2030 rows of dead, flat, keratinized membranous sacs F Three-quarters of the epidermal thickness F Functions F Protects from abrasion and penetration F Waterproofs F Barrier against biological, chemical, and physical assaults Figure 5.2b Melanocyte Melanin granule Tactile (Merkel) cell Sensory nerve ending Epidermal dendritic cell Dermis Keratinocytes Stratum corneum Most superficial layer; 2030 layers of dead cells represented only by flat membranous sacs filled with keratin. Glycolipids in extracellular space. Stratum granulosum Three to five layers of flattened cells, organelles deteriorating; cytoplasm full of lamellated granules (release lipids) and keratohyaline granules. 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 epidermal dendritic cells. Desmosomes (b) Dermis F Strong, flexible connective tissue F Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells F Two layers: F Papillary F Reticular F Strong, flexible connective tissue F Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells F Two layers: F Papillary F Reticular Figure 5.1 Epidermis Hair shaft Dermis Reticular layer Papillary layer Hypodermis (superficial fascia) Dermal papillae Pore Subpapillary vascular plexus Appendages of skin Eccrine sweat gland Arrector pili muscle Sebaceous (oil) gland Hair follicle Hair root Nervous structures Sensory nerve fiber Pacinian corpuscle Hair follicle receptor (root hair plexus) Cutaneous vascular plexus Adipose tissue Layers of the Dermis: Papillary Layer F Papillary layer F Areolar connective tissue with collagen and elastic fibers and blood vessels F Dermal papillae contain: F Capillary loops F Meissners corpuscles F Free nerve endings F Papillary layer F Areolar connective tissue with collagen and elastic fibers and blood vessels F Dermal papillae contain: F Capillary loops F Meissners corpuscles F Free nerve endings Layers of the Dermis: Reticular Layer F Reticular layer F ~80% of the thickness of dermis F Collagen fibers provide strength and resiliency F Elastic fibers provide stretch-recoil properties F Reticular layer F ~80% of the thickness of dermis F Collagen fibers provide strength and resiliency F Elastic fibers provide stretch-recoil properties Skin Markings: Friction Ridges F Epidermal ridges lie atop deeper dermal papillary ridges to form friction ridges of fingerprints Figure 5.4a Friction ridges (a) Openings of sweat gland ducts Skin Markings: Cleavage Lines F Collagen fibers arranged in bundles form cleavage (tension) lines F Incisions made parallel to cleavage lines heal more readily F Collagen fibers arranged in bundles form cleavage (tension) lines F Incisions made parallel to cleavage lines heal more readily Figure 5.4b (b) Skin Color F Three pigments contribute to skin color: 1. Melanin F Yellow to reddish-brown to black, responsible for dark skin colors F Produced in melanocytes; migrates to keratinocytes where it forms pigment shields for nuclei F Freckles and pigmented moles F Local accumulations of melanin F Three pigments contribute to skin color: 1. Melanin F Yellow to reddish-brown to black, responsible for dark skin colors F Produced in melanocytes; migrates to keratinocytes where it forms pigment shields for nuclei F Freckles and pigmented moles F Local accumulations of melanin Skin Color 2. Carotene F Yellow to orange, most obvious in the palms and soles 3. Hemoglobin F Responsible for the pinkish hue of skin 2. Carotene F Yellow to orange, most obvious in the palms and soles 3. Hemoglobin F Responsible for the pinkish hue of skin Appendages of the Skin F Derivatives of the epidermis F Sweat glands F Oil glands F Hairs and hair follicles F Nails F Derivatives of the epidermis F Sweat glands F Oil glands F Hairs and hair follicles F Nails Sweat Glands F Two main types of sweat (sudoriferous) glands 1. Eccrine (merocrine) sweat glands abundant on palms, soles, and forehead F Sweat: 99% water, NaCl, vitamin C, antibodies, dermcidin, metabolic wastes F Ducts connect to pores F Function in thermoregulation F Two main types of sweat (sudoriferous) glands 1. Eccrine (merocrine) sweat glands abundant on palms, soles, and forehead F Sweat: 99% water, NaCl, vitamin C, antibodies, dermcidin, metabolic wastes F Ducts connect to pores F Function in thermoregulation Figure 5.5b (b) Photomicrograph of a sectioned eccrine gland (220x) Secretory cells Dermal connective tissue Duct Sebaceous gland Sweat pore Eccrine gland Sweat Glands 2. Apocrine sweat glandsconfined to axillary and anogenital areas F Sebum: sweat + fatty substances and proteins F Ducts connect to hair follicles F Functional from puberty onward (as sexual scent glands?) F Specialized apocrine glands F Ceruminous glandsin external ear canal; secrete cerumen F Mammary glands 2. Apocrine sweat glandsconfined to axillary and anogenital areas F Sebum: sweat + fatty substances and proteins F Ducts connect to hair follicles F Functional from puberty onward (as sexual scent glands?) F Specialized apocrine glands F Ceruminous glandsin external ear canal; secrete cerumen F Mammary glands Sebaceous (Oil) Glands F Widely distributed F Most develop from hair follicles F Become active at puberty F Sebum F Oily holocrine secretion F Bactericidal F Softens hair and skin F Widely distributed F Most develop from hair follicles F Become active at puberty F Sebum F Oily holocrine secretion F Bactericidal F Softens hair and skin Figure 5.5a (a) Photomicrograph of a sectioned sebaceous gland (220x) Sebaceous gland duct Hair in hair follicle Secretory cells Dermal connective tissue Sebaceous gland Sweat pore Eccrine gland Hair F Functions F Alerting the body to presence of insects on the skin F Guarding the scalp against physical trauma, heat loss, and sunlight F Distribution F Entire surface except palms, soles, lips, nipples, and portions of external genitalia F Functions F Alerting the body to presence of insects on the skin F Guarding the scalp against physical trauma, heat loss, and sunlight F Distribution F Entire surface except palms, soles, lips, nipples, and portions of external genitalia Hair F Consists of dead keratinized cells F Contains hard keratin; more durable than soft keratin of skin F Hair pigments: melanins (yellow, rust brown, black) F Gray/white hair: decreased melanin production, increased air bubbles in shaft F Consists of dead keratinized cells F Contains hard keratin; more durable than soft keratin of skin F Hair pigments: melanins (yellow, rust brown, black) F Gray/white hair: decreased melanin production, increased air bubbles in shaft Figure 5.6a Hair shaft Arrector pili Sebaceous gland Hair 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 (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 Arrector pili Sebaceous gland Hair root Hair bulb Figure 5.6b Hair Follicle F Extends from the epidermal surface into dermis F Two-layered wall: outer connective tissue root sheath, inner epithelial root sheath F Hair bulb: expanded deep end F Extends from the epidermal surface into dermis F Two-layered wall: outer connective tissue root sheath, inner epithelial root sheath F Hair bulb: expanded deep end Hair Follicle F Hair follicle receptor (root hair plexus) F Sensory nerve endings around each hair bulb F Stimulated by bending a hair F Arrector pili F Smooth muscle attached to follicle F Responsible for goose bumps F Hair follicle receptor (root hair plexus) F Sensory nerve endings around each hair bulb F Stimulated by bending a hair F Arrector pili F Smooth muscle attached to follicle F Responsible for goose bumps Figure 5.6c Hair shaft Arrector pili Sebaceous gland Hair root Hair bulb (c)Diagram of a longitudinal view of the expanded hair bulb of the follicle, which encloses the matrix Internal epithelial root sheath External epithelial root sheath Connective tissue root sheath Follicle wall Hair matrix Melanocyte Hair papilla Subcutaneous adipose tissue Medulla Cortex Cuticle Glassy membrane Hair root (d) Photomicrograph of longitudinal view of the hair bulb in the follicle (160x) Follicle wall Hair matrix Hair papilla Subcutaneous adipose tissue Hair root Connective tissue root sheath Glassy membrane External epithelial root sheath Internal epithelial root sheath Cuticle Cortex Medulla Hair shaft Arrector pili Sebaceous gland Hair root Hair bulb Figure 5.6d Types of Hair F Velluspale, fine body hair of children and adult females F Terminalcoarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males) F Velluspale, fine body hair of children and adult females F Terminalcoarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males) Types of Hair F Hair Growth F Growth phase (weeks to years) followed by regressive stage and resting phase (13 months) F Growth phase varies (610 years in scalp, 34 months in eyebrows) F Hair Growth F Growth phase (weeks to years) followed by regressive stage and resting phase (13 months) F Growth phase varies (610 years in scalp, 34 months in eyebrows) Hair Thinning and Baldness F Alopeciahair thinning in both sexes after age 40 F True (frank) baldness F Genetically determined and sex-influenced condition F Male pattern baldness is caused by follicular response to DHT F Alopeciahair thinning in both sexes after age 40 F True (frank) baldness F Genetically determined and sex-influenced condition F Male pattern baldness is caused by follicular response to DHT Structure of a Nail F Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes Figure 5.7 Lateral nail fold Lunule Nail matrix Root of nail Proximal nail fold Hyponychium Nail bed Phalanx (bone of fingertip) Eponychium (cuticle) Body of nail Free edge of nail (a) (b) Functions of the Integumentary System 1. Protectionthree types of barriers F Chemical F Low pH secretions (acid mantle) and defensins retard bacterial activity 1. Protectionthree types of barriers F Chemical F Low pH secretions (acid mantle) and defensins retard bacterial activity Functions of the Integumentary System F Physical/mechanical barriers F Keratin and glycolipids block most water and water- soluble substances F Limited penetration of skin by lipid-soluble substances, plant oleoresins (e.g., poison ivy), organic solvents, salts of heavy metals, some drugs F Biological barriers F Dendritic cells, macrophages, and DNA F Physical/mechanical barriers F Keratin and glycolipids block most water and water- soluble substances F Limited penetration of skin by lipid-soluble substances, plant oleoresins (e.g., poison ivy), organic solvents, salts of heavy metals, some drugs F Biological barriers F Dendritic cells, macrophages, and DNA Functions of the Integumentary System 2. Body temperature regulation F ~500 ml/day of routine insensible perspiration (at normal body temperature) F At elevated temperature, dilation of dermal vessels and increased sweat gland activity (sensible perspirations) cool the body 3. Cutaneous sensations F Temperature, touch, and pain 2. Body temperature regulation F ~500 ml/day of routine insensible perspiration (at normal body temperature) F At elevated temperature, dilation of dermal vessels and increased sweat gland activity (sensible perspirations) cool the body 3. Cutaneous sensations F Temperature, touch, and pain Functions of the Integumentary System 4. Metabolic functions F Synthesis of vitamin D precursor and collagenase F Chemical conversion of carcinogens and some hormones 5. Blood reservoirup to 5% of bodys blood volume 6. Excretionnitrogenous wastes and salt in sweat 4. Metabolic functions F Synthesis of vitamin D precursor and collagenase F Chemical conversion of carcinogens and some hormones 5. Blood reservoirup to 5% of bodys blood volume 6. Excretionnitrogenous wastes and salt in sweat Skin Cancer F Most skin tumors are benign (do not metastasize) F Risk factors F Overexposure to UV radiation F Frequent irritation of the skin F Some skin lotions contain enzymes in liposomes that can fix damaged DNA F Most skin tumors are benign (do not metastasize) F Risk factors F Overexposure to UV radiation F Frequent irritation of the skin F Some skin lotions contain enzymes in liposomes that can fix damaged DNA Skin Cancer F Three major types: F Basal cell carcinoma F Least malignant, most common F Squamous cell carcinoma F Second most common F Melanoma F Most dangerous F Three major types: F Basal cell carcinoma F Least malignant, most common F Squamous cell carcinoma F Second most common F Melanoma F Most dangerous Basal Cell Carcinoma F Stratum basale cells proliferate and slowly invade dermis and hypodermis F Cured by surgical excision in 99% of cases F Stratum basale cells proliferate and slowly invade dermis and hypodermis F Cured by surgical excision in 99% of cases Figure 5.8a Squamous Cell Carcinoma F Involves keratinocytes of stratum spinosum F Most common on scalp, ears, lower lip, and hands F Good prognosis if treated by radiation therapy or removed surgically F Involves keratinocytes of stratum spinosum F Most common on scalp, ears, lower lip, and hands F Good prognosis if treated by radiation therapy or removed surgically Figure 5.8b Melanoma F Involves melanocytes F Highly metastatic and resistant to chemotherapy F Treated by wide surgical excision accompanied by immunotherapy F Involves melanocytes F Highly metastatic and resistant to chemotherapy F Treated by wide surgical excision accompanied by immunotherapy Melanoma F 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) F 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) Figure 5.8c Burns F Heat, electricity, radiation, certain chemicals Burn (tissue damage, denatured protein, cell death) F Immediate threat: F Dehydration and electrolyte imbalance, leading to renal shutdown and circulatory shock F Heat, electricity, radiation, certain chemicals Burn (tissue damage, denatured protein, cell death) F Immediate threat: F Dehydration and electrolyte imbalance, leading to renal shutdown and circulatory shock Rule of Nines F Used to estimate the volume of fluid loss from burns Figure 5.9 Anterior and posterior head and neck, 9% 4 1 / 2 % 4 1 / 2 % Anterior and posterior upper limbs, 18% Anterior and posterior lower limbs, 36% 100% Totals Anterior and posterior trunk, 36% Anterior trunk, 18% 9% (Perineum, 1%) 4 1 / 2 % Partial-Thickness Burns F First degree F Epidermal damage only F Localized redness, edema (swelling), and pain F Second degree F Epidermal and upper dermal damage F Blisters appear F First degree F Epidermal damage only F Localized redness, edema (swelling), and pain F Second degree F Epidermal and upper dermal damage F Blisters appear Figure 5.10a (a)Skin bearing partial thickness burn (1st and 2nd degree burns) 1st degree burn 2nd degree burn Full-Thickness Burns F Third degree F Entire thickness of skin damaged F Gray-white, cherry red, or black F No initial edema or pain (nerve endings destroyed) F Skin grafting usually necessary F Third degree F Entire thickness of skin damaged F Gray-white, cherry red, or black F No initial edema or pain (nerve endings destroyed) F Skin grafting usually necessary Figure 5.10b (b)Skin bearing full thickness burn (3rd degree burn) 3rd degree burn Severity of Burns F Critical if: F >25% of the body has second-degree burns F >10% of the body has third-degree burns F Face, hands, or feet bear third-degree burns F Critical if: F >25% of the body has second-degree burns F >10% of the body has third-degree burns F Face, hands, or feet bear third-degree burns Developmental Aspects: Fetal F Ectoderm epidermis F Mesoderm dermis and hypodermis F Lanugo coat: covering of delicate hairs in 5th and 6th month F Vernix caseosa: sebaceous gland secretion; protects skin of fetus F Ectoderm epidermis F Mesoderm dermis and hypodermis F Lanugo coat: covering of delicate hairs in 5th and 6th month F Vernix caseosa: sebaceous gland secretion; protects skin of fetus Developmental Aspects: Adolescent to Adult F Sebaceous gland activity increases F Effects of cumulative environmental assaults show after age 30 F Scaling and dermatitis become more common F Sebaceous gland activity increases F Effects of cumulative environmental assaults show after age 30 F Scaling and dermatitis become more common Developmental Aspects: Old Age F Epidermal replacement slows, skin becomes thin, dry, and itchy F Subcutaneous fat and elasticity decrease, leading to cold intolerance and wrinkles F Increased risk of cancer due to decreased numbers of melanocytes and dendritic cells F Epidermal replacement slows, skin becomes thin, dry, and itchy F Subcutaneous fat and elasticity decrease, leading to cold intolerance and wrinkles F Increased risk of cancer due to decreased numbers of melanocytes and dendritic cells