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PowerPoint® Lecture Slides prepared by Betsy C. Brantley Valencia College CHAPTER 4 The Integumentary System © 2013 Pearson Education, Inc. Chapter 4 Learning Outcomes • Section 1: Functional Anatomy of the Skin • 4.1 • Describe the main structural features of the epidermis, and explain the functional significance of each. • 4.2 • Explain what accounts for individual differences in skin color and compare various types of skin cancer. • 4.3 • Describe the structure and functions of the dermis and hypodermis. • 4.4 • Describe the interaction between sunlight and endocrine functioning as they relate to the skin. © 2013 Pearson Education, Inc. Chapter 4 Learning Outcomes • Section 2: Accessory Organs of the Skin • 4.5 • Explain the mechanisms of hair production, and explain the structural basis for hair texture and color. • 4.6 • Describe the various kinds of exocrine glands in the skin, and discuss the secretions of each. • 4.7 • Explain the anatomy of a typical nail. • 4.8 • CLINICAL MODULE Summarize the effects of aging on the skin. • 4.9 • CLINICAL MODULE Explain how the skin responds to injury and the steps by which it repairs itself. © 2013 Pearson Education, Inc. Functional Anatomy of the Skin (Section 1) • Integumentary system (integument) • Body's first line of defense • Composed of: • Cutaneous membrane (skin) • Accessory structures (hair, nails, exocrine glands) © 2013 Pearson Education, Inc. Cutaneous Membrane (Section 1) • Epidermis • Stratified squamous epithelium • Dermis • Papillary layer of areolar tissue • Reticular layer of dense irregular connective tissue • Hypodermis or subcutaneous layer • Connective tissue deep to integument © 2013 Pearson Education, Inc. Accessory Structures (Section 1) • Include: • Hair • Nails • Exocrine glands • Cutaneous plexus • Network of arteries and veins associated with integumentary tissues © 2013 Pearson Education, Inc. Functional anatomy of the skin Cutaneous Membrane Accessory Structures Hair shaft Epidermis Dermis Pore of sweat gland duct Papillary layer Reticular layer Touch and pressure receptors Sebaceous gland Arrector pili muscle Sweat gland duct Hair follicle Hypodermis, or subcutaneous layer Nerve fibers Sweat gland Fat © 2013 Pearson Education, Inc. Artery Vein Figure 4 Section 1 1 1 Integumentary System Functions (Section 1) • Protection • Protects underlying tissues and organs from impact, abrasion, fluid loss, chemical attack • Produces melanin, which protects underlying tissue from UV radiation • Produces keratin, which protects against abrasion and repels water • Coordinates immune response to pathogens and skin cancer • Excretion • Excretes salts, water, organic wastes © 2013 Pearson Education, Inc. Integumentary System Functions (Section 1) • Body temperature regulation • Maintains normal body temperature through insulation or evaporative cooling • Vitamin D3 synthesis • Converted to calcitriol, important in calcium metabolism • Lipid storage • Stored in adipocytes in dermis and hypodermis • Sensory input • Detects touch, pressure, pain, temperature © 2013 Pearson Education, Inc. Epidermis (4.1) • Primary cell type in epidermis is keratinocyte • Body's most abundant epithelial cell • Multiple layers of cells (stratified squamous epithelium) • Stem cells in deepest layers • Keratinocytes shed at exposed surface • Epidermal ridges adjacent to dermal papillae • Increase surface area for better attachment © 2013 Pearson Education, Inc. Dermal papillae Epidermis Epidermal ridge Dermal papilla Dermis © 2013 Pearson Education, Inc. Figure 4.1 11 Thin Skin (4.1) • Covers most of body surface • Four strata (layers) • Epidermis as thick as a plastic sandwich bag (~0.08 mm) © 2013 Pearson Education, Inc. Micrograph of thin skin Epidermis Dermis Thin skin LM x 225 © 2013 Pearson Education, Inc. Figure 4.1 22 Thick Skin (4.1) • Found on palms of hands and soles of feet • Five strata (layers) • Epidermis as thick as a paper towel (~0.5 mm) © 2013 Pearson Education, Inc. Micrograph of thick skin Epidermis Dermal papilla Epidermal ridge Thick skin © 2013 Pearson Education, Inc. LM x 225 Figure 4.1 33 Characteristics of the Epidermis (4.1) • Entire epidermis lacks blood vessels • Cells get oxygen and nutrients from dermis • Cells with highest metabolic demand closest to dermis • Takes 7–10 days for cells to move from deepest layer (stratum basale) to most superficial layer (stratum corneum) © 2013 Pearson Education, Inc. Layers of the Epidermis (4.1) • Stratum basale • Deepest layer of epidermis • Attached to basement membrane by hemidesmosomes • Most cells here are basal cells, stem cells that divide to replace more superficial keratinocytes • Merkel cells that respond to touch are also found here • Stratum spinosum • "Spiny layer" composed of 8–10 layers of keratinocytes • Only looks spiny when on a prepared slide • Contains dendritic cells, part of immune response © 2013 Pearson Education, Inc. Layers of the Epidermis (4.1) • Stratum granulosum • "Grainy layer" composed of 3–5 layers of keratinocytes • Most cells have stopped dividing and started making keratin • Cells grow thinner, flatter with thick and less permeable membranes • Stratum lucidum • "Clear layer" found only in thick skin • Layer of flattened, densely packed dead cells filled with keratin • Stratum corneum • 15–30 layers of keratinized cells (filled with keratin) • Cells are dead but still tightly connected by desmosomes © 2013 Pearson Education, Inc. Layers of the epidermis Layers of the Epidermis Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale Papillary layer of dermis LM x 470 © 2013 Pearson Education, Inc. 4 Figure 4.1 34 Fingerprints (4.1) • Ridge patterns in thick skin on surface of fingertips • Pattern produces fingerprints • Fingerprints used to identify individuals © 2013 Pearson Education, Inc. Ridges patterns on fingertips SEM x 25 © 2013 Pearson Education, Inc. 4 Figure 4.1 35 Module 4.1 Review a. Identify the layers of the epidermis of thick skin (from deep to superficial). b. Dandruff is caused by excessive shedding of cells from the outer layers of the skin of scalp. Thus, dandruff is composed of cells from which epidermal layer? c. A splinter penetrates to the third layer of the epidermis of the palm. In which layer does it lodge? © 2013 Pearson Education, Inc. Skin Color (4.2) • Skin color is determined by: • Pigments in the skin • Carotene • Melanin • Degree of dermal circulation • Difference in skin pigmentation results from different levels of pigment production, not different numbers of melanocytes © 2013 Pearson Education, Inc. Epidermal pigmentation Melanocytes in stratum basale Melanin pigment Basement membrane Thin skin © 2013 Pearson Education, Inc. LM x 400 4 Figure 4.2 31 Skin Pigments (4.2) • Carotene • Orange-yellow pigment • Most apparent in stratum corneum of light-skinned people • Found in orange vegetables • Melanin • Brown, yellow-brown, or black pigment • Produced by melanocytes, located in stratum basale • Packaged into melanosomes; transferred to keratinocytes where it offers protection for nucleus against UV radiation • Larger melanosomes result in darker skinned individuals © 2013 Pearson Education, Inc. A melanocyte in the stratum basale 3 Keratinocyte 1 Melanosomes transferred to keratinocytes Melanin produced by melanocytes 2 4 Carotene is an orange-yellow pigment Melanin packaged in melanosomes Basement membrane © 2013 Pearson Education, Inc. 4 Figure 4.2 31 Dermal Circulation (4.2) • Hemoglobin is red pigment found in red blood cells • Blood flows to dermis through papillary plexus • More blood flow to region results in redder color • Flushed skin with fever from dilated superficial blood vessels • Less blood flow to region results in cyanosis • Lower oxygen levels makes hemoglobin darker red • From surface view, skin has bluish color • Most apparent in very thin skin (lips, beneath nails) © 2013 Pearson Education, Inc. Dermal circulation affects skin color Hair Capillary loop of papillary plexus Papillary plexus Papillary layer Cutaneous plexus © 2013 Pearson Education, Inc. 4 Figure 4.2 32 Skin Cancers (4.2) • Skin cancers most common types of cancers • Basal cell carcinoma • Most common form of skin cancer • Originates in stratum basale and rarely metastasizes • Result of mutation caused by overexposure to UV radiation • Squamous cell carcinoma • Second most common form of skin cancer • Found in areas of sun-exposed skin • More likely to metastasize than basal cell carcinoma • Treatment for both types is surgical removal of tumor © 2013 Pearson Education, Inc. Basal cell carcinoma © 2013 Pearson Education, Inc. 4 Figure 4.2 33 Malignant Melanoma (4.2) • Most serious form of skin cancer • Cancerous melanocytes grow rapidly and metastasize through lymphatic system • If detected early and removed surgically, the 5-year survival rate is 99 percent • If not detected until after metastasis, the 5-year survival rate is 14 percent • Key characteristics • Irregular in shape, border, color • More than 5 mm in diameter • Raised beyond skin surface © 2013 Pearson Education, Inc. Malignant melanoma © 2013 Pearson Education, Inc. 4 Figure 4.2 34 Module 4.2 Review a. Name the two pigments contained in the epidermis. b. Why does exposure to sunlight or sunlamps darken skin? c. Rank the three skin cancers according to their health risk. © 2013 Pearson Education, Inc. Dermis (4.3) • Between epidermis and hypodermis • Two fiber types 1. Elastic fibers stretch and recoil to original length • Allow flexibility in dermis 2. Collagen fibers are strong, resist stretching, and bend easily • Limit flexibility in dermis and prevent damage © 2013 Pearson Education, Inc. Epidermis, dermis, and hypodermis Epidermal ridges Dermal papillae Papillary layer Reticular layer Capillary network Hypodermis © 2013 Pearson Education, Inc. 4 Figure 4.3 31 Dermal Layers (4.3) • Papillary layer (named after dermal papillae) • Composed of areolar tissue • Contains capillaries, lymphatic vessels, sensory neurons, and touch receptors • Reticular layer • Interwoven meshwork of dense irregular connective tissue • Collagen fibers from this layer blend into both papillary layer above and hypodermis below • Contains blood vessels, nerve fibers, and accessory organs © 2013 Pearson Education, Inc. Micrograph of reticular layer of dermis Reticular layer of dermis SEM x 1500 © 2013 Pearson Education, Inc. 4 Figure 4.3 32 Hypodermis (4.3) • Separates skin from deeper structures • Stabilizes position of skin relative to underlying tissues • Often dominated by adipose tissue • Site for storing energy © 2013 Pearson Education, Inc. Micrograph of hypodermis Adipocytes Hypodermis © 2013 Pearson Education, Inc. SEM x 250 4 Figure 4.3 33 Module 4.3 Review a. Describe the location of the dermis. b. Where are the capillaries and sensory neurons that supply the epidermis located? c. What accounts for the ability of the dermis to undergo repeated stretching? © 2013 Pearson Education, Inc. Vitamin D and Sunlight (4.4) • Two sources of vitamin D3 • Sunlight • Epidermal cells in stratum spinosum and stratum basale convert steroid compound into vitamin D3 • Vitamin diffuses across basement membrane and into capillaries • Diet • Fish, fish oils, shellfish • Foods "fortified with vitamin D" like milk and orange juice © 2013 Pearson Education, Inc. Vitamin D and Calcium (4.4) • Liver converts vitamin D3 to intermediary product • Kidney uses that product to synthesize calcitriol • Calcitriol stimulates calcium and phosphorus absorption by small intestines • Bones use calcium and phosphorus for growth and maintenance © 2013 Pearson Education, Inc. Sources of Vitamin D Sources of Vitamin D3 Food Sunlight Steroid compound Epidermis Vitamin D3 Dietary vitamin D3 Digestive tract Liver Intermediary product Stimulates calcium and phosphorus absorption Calcitriol Kidney © 2013 Pearson Education, Inc. 4 Figure 4.4 31 Inadequate Vitamin D (4.4) • Lack of sunlight exposure and low vitamin D3 in diet • Inadequate vitamin D3 means inadequate calcium and phosphorus • Results in flexible, poorly mineralized bone • In a growing child, causes rickets • In adults, causes decreased bone density and increased risk of fractures • Elderly at higher risk with 75 percent decline in skin production of vitamin D3 © 2013 Pearson Education, Inc. Patient with rickets © 2013 Pearson Education, Inc. 4 Figure 4.4 32 Module 4.4 Review a. Describe two sources of vitamin D3. b. Explain the relationship between sunlight exposure and vitamin D3. c. In some cultures, females must be covered from head to toe when they go outdoors. Explain why these women are at increased risk of developing bone problems later in life. © 2013 Pearson Education, Inc. Accessory Organs of the Skin (Section 2) • Hair follicles • Exocrine glands • Nails © 2013 Pearson Education, Inc. Integumentary system components Epidermis • Protects dermis from trauma and chemicals • Controls skin permeability and prevents water loss • Prevents entry of pathogens • Synthesizes vitamin D3 • Sensory receptors detect touch, pressure, pain, and temperature • Coordinates immune response to pathogens and skin cancers Cutaneous membrane Integumentary System • Protects from environmental hazards • Excretes salts, water, and wastes • Maintains body temperature (thermoregulation) • Produces melanin • Produces keratin • Synthesizes vitamin D3 • Stores lipids • Detects sensory information • Coordinates immune response Dermis Papillary Layer Reticular Layer • Nourishes and supports epidermis • Restricts spread of pathogens that penetrate epidermis • Stores lipid reserves • Attaches skin to deeper tissues • Sensory receptors detect touch, pressure, pain, vibration, and temperature • Blood vessels assist in thermoregulation Hair Follicles • Produce hairs that protect skull • Produce hairs that provide delicate touch sensations on general body surface Exocrine Glands • Assist in thermoregulation • Excrete wastes • Lubricate epidermis Accessory structures Nails • Protect and support tips of fingers and toes © 2013 Pearson Education, Inc. Figure 4 Section 2 1 1 Hair (4.5) • Found almost everywhere on body • Produced by hair follicle • Follicle composed of epithelial and connective tissues • Parts of a hair • Hair shaft is partly visible on the surface • Hair root anchors hair into skin • Root hair plexus is group of sensory nerves surrounding base of follicle • Arrector pili is smooth muscle attached to follicle; contraction causes "goosebumps" © 2013 Pearson Education, Inc. Single hair follicle Sebaceous gland Hair shaft Hair root Connective tissue sheath Root hair plexus Arrector pili muscle © 2013 Pearson Education, Inc. 4 Figure 4.5 31 Hair Structure (4.5) • Hair papilla • Peg of connective tissue filled with blood vessels and nerves at base of follicle • Matrix • Growth zone of hair • Medulla • Core of hair at center of hair matrix • Cortex • Intermediate layer deep to cuticle • Cuticle • Forms surface of the hair © 2013 Pearson Education, Inc. Sectional view of hair follicle Cuticle Cortex Medulla Matrix Hair papilla © 2013 Pearson Education, Inc. 4 Figure 4.5 32 Keratin in Hair (4.5) • Medulla • Contains flexible, soft keratin • Cortex • Contains thick layers of hard keratin • Gives hair stiffness • Cuticle • Contains very hard keratin • Very tough © 2013 Pearson Education, Inc. Hair follicle structures with cross section Sebaceous gland Hair Structure Medulla Cortex Cuticle Hair shaft Hair follicle Hair root Connective tissue sheath Root hair plexus Arrector pili muscle © 2013 Pearson Education, Inc. Figure 4.5 11- 3– 3 Hair Growth Cycle (4.5) • Hairs grow and are shed in the hair growth cycle • Active phase • Lasts 2–5 years • Hair grows at rate of 0.33 mm/day • Resting phase • Hair loses attachment to follicle • Becomes club hair • When follicle reactivated, club hair shed and replacement hair formation begins © 2013 Pearson Education, Inc. Hair growth cycle 2 Regression and transition 3 1 Active phase 2 © 2013 Pearson Education, Inc. Resting phase Follicle reactivation and growth of replacement hair 4 Figure 4.5 34 Hair Color (4.5) • Variations in hair color are due to melanin variations • Different forms of melanin give: • Dark brown • Yellow-brown • Red • Pigment production declines with age, lightening color • White hair from lack of pigment and air bubbles in medulla of hair shaft © 2013 Pearson Education, Inc. Module 4.5 Review a. Describe a typical strand of hair. b. What happens when an arrector pili muscle contracts? c. Pulling a hair is painful, but cutting a hair is not. Why? © 2013 Pearson Education, Inc. Sebaceous Glands (4.6) • Discharge sebum through holocrine secretion • Mixture of triglycerides, cholesterol, proteins, and electrolytes • Coats hair shaft and surrounding epidermal surfaces • Provides lubrication • Keeps hair shaft from becoming dry and brittle • Has antibacterial properties • Contraction of arrector pili muscles squeezes sebaceous glands, forcing sebum into hair follicle • Also secrete sebum onto skin surface on face, back, chest, nipples, and external genitalia © 2013 Pearson Education, Inc. Sebaceous glands Sebaceous Glands Typical Sebaceous Glands Sebaceous gland Sebaceous Follicles Hair removed Wall of hair follicle Basement membrane Discharge of sebum Lumen Breakdown of cell membranes Mitosis and growth Basal cells © 2013 Pearson Education, Inc. 4 Figure 4.6 31 Sweat Glands (4.6) • Apocrine sweat glands • Found in armpits, nipples, pubic region • Secrete onto hair follicles • Produce sticky, cloudy, odorous secretion • Merocrine sweat glands • Found all over body; highest concentration in palms and soles • Secrete directly onto skin surface • Produce watery secretions with electrolytes to help regulate body temperature © 2013 Pearson Education, Inc. Sweat glands Sweat Glands Apocrine Sweat Glands Connective tissue of dermis Apocrine gland cells Merocrine Sweat Glands Merocrine gland cells Lumen Lumen Section LM x 375 of apocrine sweat gland © 2013 Pearson Education, Inc. Sweat pore Section LM x 210 of merocrine sweat gland 4 Figure 4.6 32 Module 4.6 Review a. Identify two types of exocrine glands found in the skin. b. What are the functions of sebaceous secretions? c. Deodorants are used to mask the effects of secretions from which type of skin gland? © 2013 Pearson Education, Inc. Nails (4.7) • Protect tips of fingers and toes • Nail body is thick sheets of dead, keratinized epidermal cells • Nail bed is area of epidermis under nail body • Nail production occurs at nail root • Cuticle is portion of stratum corneum of nail extending over nail root • Pale arched area near nail root is lunula © 2013 Pearson Education, Inc. Common landmarks of nail structure 1 Nail bed Nail body Direction of growth Free edge of nail body 3 2 Underlying blood vessels give the nail its pink appearance. Lunula Proximal nail fold Cuticle 4 5 Proximal nail fold Phalanx (bone of fingertip) Cuticle Lunula Nail body Nail root Epidermis Dermis Phalanx © 2013 Pearson Education, Inc. 4 Figure 4.7 31 Changes in Nail Appearance (4.7) • Any health condition altering body metabolism may alter nail appearance • Changes in nail shape, structure, or appearance give diagnostic information • Psoriasis causes rapid stem cell division at stratum basale, resulting in distorted and pitted nails • Concave nails may be from blood disorder © 2013 Pearson Education, Inc. Altered nail appearance with psoriasis © 2013 Pearson Education, Inc. 4 Figure 4.7 32 Module 4.7 Review a. Define nail bed. b. Describe a typical fingernail. c. Where does nail production occur? © 2013 Pearson Education, Inc. Age-Related Changes in the Integument (4.8) • Melanocyte activity declines so skin is more sensitive to sun exposure and at risk for sunburn • Sebaceous glands secrete less sebum so skin is dry and scaly • Increased risk of skin injury, tears, and infection • Basal cell activity declines so there are fewer epidermal cells • Weakened connections between epidermis and dermis • Declining metabolic activity (less vitamin D3 production) © 2013 Pearson Education, Inc. Age-Related Changes in the Integument (4.8) • Decreasing numbers of dendritic cells decrease immune response • Dermis thins and has fewer elastic fibers resulting in sagging and wrinkling • Merocrine sweat glands are less active so there is a greater risk of overheating • Reduced blood supply to dermis affects temperature regulation © 2013 Pearson Education, Inc. Age-Related Changes in the Integument (4.8) • Skin repair slows • Hair follicles stop functioning or produce thinner hair • Decreased melanocyte activity, so gray or white hairs • Changing levels of sex hormones alter hair and fat distribution © 2013 Pearson Education, Inc. Age-related changes in the integument Fewer Melanocytes Drier Epidermis Thinning Epidermis Diminished Immune Response Thinning Dermis Decreased Perspiration Altered Hair and Fat Distribution © 2013 Pearson Education, Inc. Fewer Active Follicles Slower Skin Repair Reduced Blood Supply Figure 4.8 3 Module 4.8 Review a. Identify some common effects of the aging process on skin. b. Why does hair turn white or gray with age? c. Why do we tolerate summer heat less well and become more susceptible to heat-related illness when we become older? © 2013 Pearson Education, Inc. Integument Repair (4.9) • Initial injury to skin causes bleeding and release of mast cells • After several hours: • Blood clot or scab forms at surface • Cells of stratum basale migrate along wound edges • Macrophages remove debris • If damage into dermis, combination of fibroblasts, blood clot, and capillary network form granulation tissue as part of repair process © 2013 Pearson Education, Inc. Integument Repair (4.9) • After one week: • Scab undermined by migrating epidermal cells • Phagocytic activity almost complete • Blood clot disintegrating • Fibroblasts have formed collagen fibers and ground substance • After several weeks: • Scab is shed; epidermis is complete • Shallow depression marks injury site • Fibroblasts continue to create scar tissue – inflexible, fibrous, noncellular material © 2013 Pearson Education, Inc. Repair of injury to the integument After One Week Initial Injury After Several Hours Mast cells trigger inflammatory Bleeding response occurs at the site of injury. Scab forms at the surface Epidermis Patrolling macrophages Dermis Rapid cell division and migration along wound edges After Several Weeks Deeper portions of the clot dissolve. Fibroblasts deposit collagen fibers and ground substance. Fibroblasts Scar tissue formation Scar tissue Formation of granulation tissue © 2013 Pearson Education, Inc. Figure 4.9 11- 4– 4 Scar Tissue (4.9) • Formation of scar tissue part of tissue repair • Hair follicles, sebaceous or sweat glands, muscle cells, nerves often replaced by scar tissue • Scar tissue forming beyond repair area is keloid • Harmless raised, thickened mass of scar tissue • Covered by shiny, smooth epidermal surface • Most common on upper back, shoulders, anterior chest, earlobes © 2013 Pearson Education, Inc. Adult with keloid scar tissue © 2013 Pearson Education, Inc. 4 Figure 4.9 35 Module 4.9 Review a. Identify the first step in the repair of an injury to the skin. b. Describe granulation tissue. c. Why can skin regenerate effectively even after considerable damage? © 2013 Pearson Education, Inc.