Human Anatomy Chapter 5 Integumentary System PDF

Because learning changes everything.® Chapter 5 Integumentary System Human Anatomy SIXTH EDITION McKinley O’Loughlin Pennefather-O’Brien © 2021 McGraw Hill. All rights reserved. Authorized o...

Because learning changes everything.® Chapter 5 Integumentary System Human Anatomy SIXTH EDITION McKinley O’Loughlin Pennefather-O’Brien © 2021 McGraw Hill. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw Hill.  Outline Structure and Functions of the Integument Epidermis Dermis Subcutaneous Layer Integumentary Structures Derived from Epidermis Integument Repair and Regeneration Aging of the Integument Development of the Integumentary System © McGraw Hill 2  Introduction The integument is the skin that covers your body Also known as the cutaneous membrane Integumentary system is the skin and its derivatives (nails, hair, sweat glands, sebaceous glands) © McGraw Hill 3  Integument Structure Two layers of the integument: Epidermis: superficial layer of stratified squamous epithelium Dermis: deeper layer of areolar and dense irregular connective tissues Subcutaneous layer: not part of skin; lies under dermis; composed of areolar and adipose tissue © McGraw Hill 4  Layers of the Integument Figure 5.1 © McGraw Hill 5  Integument Functions 1 Functions of the integument: Protection Protects against trauma, toxic substances, and solar radiation Some chemicals can be absorbed Selective permeability Prevention of water loss and gain Skin is water-resistant but not completely waterproof due to transepidermal water loss Includes insensible perspiration (release of water vapor from sweat glands when not visibly sweating) and sensible perspiration (visible sweating) Temperature regulation Dilation of dermal vessels releases heat, constriction conserves heat © McGraw Hill 6  Integument Functions 2 Functions of the integument, continued: Metabolic regulation Vitamin D3 is produced by some skin cells and converted to calcitriol by the kidneys Calcitriol is a hormone involved in calcium homeostasis Immune defense Epidermal dendritic cells help initiate immune responses Sensory reception Many skin receptors help detect changes in temperature, touch E.g., tactile cells stimulate sensory nerve endings in response to touch Secretion Sweating; lubrication of hair and skin with sebum © McGraw Hill 7  Epidermis The epithelium of the skin is the epidermis Keratinized stratified squamous Avascular Composed of several layers (strata) © McGraw Hill 8  Epidermal Strata 1 From deep to superficial: Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum (found only in thick skin) Stratum corneum © McGraw Hill 9  Epidermal Strata 2 Figure 5.2 © McGraw Hill (a) Ed Reschke/Photolibrary/Getty Images 10  Stratum Basale Single layer of cells, cuboidal to low columnar in appearance Cells are attached to basement membrane and adjacent to the dermis Cell types include: Keratinocytes: most abundant; produce tough keratin protein, which protects and makes skin water resistant Keratinocyte stem cells predominate; divide to replace keratinocytes shed at epidermal surface Melanocytes: produce pigment melanin, which absorbs UV light to prevent DNA damage Melanocyte cytoplasmic processes transfer melanin granules (melanosomes) to keratinocytes Tactile cells: sensitive to touch © McGraw Hill 11  Stratum Spinosum Several layers of polygonal keratinocytes Daughter cells from stratum basale differentiate into nondividing, specialized keratinocytes that make up this stratum Keratinocytes attach to each other via desmosomes Some epidermal dendritic cells present in this stratum Immune cells that act as phagocytes to fight infection and initiate immune responses © McGraw Hill 12  Stratum Granulosum Three to five layers of keratinocytes undergoing keratinization Cytoplasm fills with keratin filaments Organelles begin to degrade Two types of keratin granules in cells of this stratum Keratohyalin granules involved in keratinization process Lamellar granules that release contents (primarily lipids) into extracellular space; help form water barrier © McGraw Hill 13  Stratum Lucidum Thin, translucent region, two to three cell layers thick Present only in thick skin Palms of the hands and soles of the feet Cells lack organelles and are filled with eleidin, a transparent, intermediate product of keratin maturation © McGraw Hill 14  Stratum Corneum Most superficial stratum of epidermis Thickness varies from 20 to 30 layers of dead, scaly, interlocking keratinized cells called corneocytes Cells are anucleate (lack a nucleus) and tightly packed Cells from stratum basale take about 2 weeks to migrate to stratum corneum where they spend another 2 weeks serving to protect deeper layers Eventually shed from epidermal surface © McGraw Hill 15  Thick Skin Versus Thin Skin Thick skin contains five layers in epidermis (includes stratum lucidum) Found in palms of hands and soles of feet Epidermis is 0.4–0.6 mm thick No hair follicles or sebaceous glands Thin skin lacks stratum lucidum—has four layers in epidermis Covers most of body Epidermis is 0.075–0.150 mm thick © McGraw Hill 16  Thick Skin and Thin Skin Figure 5.3 © McGraw Hill (a) ©Lutz Slomianka; (b) Carolina Biological Supply Company/Phototake 17  Thick Skin and Thin Skin Figure 5.3 © McGraw Hill (a) ©Lutz Slomianka; (b) Carolina Biological Supply Company/Phototake 18  Skin Color Skin color is determined by three pigments: 1. Hemoglobin: blood pigment; red in color 2. Melanin: pigment produced by melanocytes Increases with exposure to ultraviolet radiation Relative amounts of two types of melanin give people different complexions All people have about same number of melanocytes 3. Carotene: yellow-orange pigment from foods such as carrots; it builds up in the skin © McGraw Hill 19  Production of Melanin by Melanocytes Figure 5.4 © McGraw Hill (b) ©McGraw-Hill Education/Al Telser, photographer 20  Abnormal Skin Colors Albinism: Hair is white, skin is pale, irises of eyes are pink Bronzing: Skin appears golden-brown, copper, or bronze in color Cyanosis: Skin appears bluish as a result of oxygen deficiency in circulating blood Erythema: Skin appears abnormally red Hematoma: A bruise (visible pool of clotted blood) is observable through the skin Jaundice: Skin and sclera (white of the eyes) appear yellowish Pallor: Skin appears ashen, pale due to white collagen fibers housed within the dermis © McGraw Hill 21  Skin Markings Nevus: also called a mole; localized overgrowth of melanocytes Freckles: yellow or brown spots of high melanocyte activity Hemangioma: proliferation of blood vessels that form a benign tumor Capillary hemangiomas (strawberry-colored birthmarks) are bright red to deep purple; usually appear in childhood Cavernous hemangiomas (port wine stains) involve larger dermal vessels and may last a lifetime Friction ridges: folds of epidermis and dermis on fingers, palms, soles, and toes; increase friction for grasping © McGraw Hill 22  Dermis Lies deep to the epidermis Composed of areolar and dense irregular connective tissues Two layers: Papillary layer: superficial; adjacent to epidermis Reticular layer: deeper and thicker layer © McGraw Hill 23  Layers of the Dermis Figure 5.6 © McGraw Hill 24  Papillary Layer of the Dermis The papillary layer is the superficial region of the dermis directly adjacent to the epidermis Composed of areolar connective tissue Dermal papillae are projections of the dermis toward the epidermis Interlock with epidermal ridges (deep projections of epidermis), increasing the surface area between epidermis and dermis Dermal papillae contain capillaries that supply nutrients to the epidermis and also contain sensory receptors © McGraw Hill 25  Reticular Layer of the Dermis The reticular layer is the deeper region of the dermis that forms the majority of its thickness Comprised mainly of dense irregular connective tissue Large collagen bundles project in all directions Includes many blood vessels, glands, hair follicles, and nerves © McGraw Hill 26  Lines of Cleavage and Stretch Marks Majority of collagen and elastic fibers are oriented in parallel bundles at specific body locations Function to resist routine stresses Lines of cleavage (tension lines) identify the orientation of these fiber bundles Important clinically, as incisions across these lines heal more slowly than incisions along these lines When skin is overstretched, collagen fibers may tear to form striae (stretch marks) © McGraw Hill 27  Lines of Cleavage Figure 5.7 © McGraw Hill 28  Innervation and Blood Supply Nerve fibers are extensively dispersed in dermis This property is called innervation Monitor sensory receptors Control blood flow Control glandular secretion Dermal blood vessels help control body temperature and blood pressure Vasoconstriction (narrowed diameter of vessels) reduces blood flow to skin, helps conserve heat Vasodilation (widening diameter of vessels) increases blood flow to skin, helps release heat © McGraw Hill 29  Subcutaneous Layer Deep to the integument Not actually part of the integument Composed of areolar and adipose connective tissues In some body areas where this layer is predominantly adipose, it’s then called subcutaneous fat Functions: Protects underlying structures Stores energy Thermal insulation © McGraw Hill 30  Integumentary Structures Derived from Epidermis Structures that are epidermal derivatives include: Nails Hair Exocrine glands of the skin © McGraw Hill 31  Hair Type and Distribution Three hair types: Lanugo: found on fetus Vellus: fine and nonpigmented, on most of body Terminal hair: coarse and pigmented © McGraw Hill 32  Hair Structure and Follicles 1 Pilus consists of keratinocytes growing from follicles deep in dermis (often projecting to subcutaneous layer) Zones that make up a hair: Hair bulb: deep swelling of epithelial cells where hair originates Hair root: portion that is deep to skin surface Hair shaft: portion that extends beyond skin surface © McGraw Hill 33  Hair Structure and Follicles 2 Hair production occurs at hair matrix A hair has different layers Medulla: core of loose cells, air spaces Cortex: several layers of hardened, flattened cells Cuticle: outer coating A hair follicle surrounds each hair Wall has connective tissue root sheath and epithelial tissue root sheath Arrector pili muscles attach to hair shaft Respond to emotions and cold temperatures by contracting, standing the hair up, therefore producing “goose bumps” © McGraw Hill 34 Hair Figure 5.9 © McGraw Hill (b) ©McGraw-Hill Education/Al Telser, photographer 35  Functions of Hair Protection—from sunburn and injury Heat retention—help prevent heat loss from head Sensory reception—detect light touch Visual identification—help determine age and sex © McGraw Hill 36  Hair Color From melanin produced in matrix adjacent to papillae Variations are genetically determined; also influenced by environment and hormonal factors Pigment production decreases with age Gray hair due to gradual melanin decrease White hair due to complete stoppage of melanin production © McGraw Hill 37  Exocrine Glands of the Skin The skin contains two types of exocrine glands: Sweat (sudoriferous) glands: produce watery solution Merocrine and apocrine Sebaceous glands: produce oily secretions Figure 5.10 (a) © McGraw Hill 38  Sweat (Sudoriferous) Glands Two types of sweat glands: merocrine sweat glands and apocrine sweat glands Have coiled, tubular secretory portion in reticular layer of dermis or in subcutaneous layer Sweat gland duct transports secretions to Skin surface for merocrine glands A hair follicle for apocrine glands Opening of duct on skin surface is called a sweat pore Myoepithelial cells (between secretory cells) respond to sympathetic stimulation; contract to squeeze the gland so secretions are released © McGraw Hill 39  Merocrine Sweat Glands Simple, coiled, tubular glands that release secretions (via exocytosis) into a duct which terminates as a pore on skin’s surface Secretion is 99% water, clear, and controlled by nervous system This secretion is called sweat Numerous on palms of hands, soles of feet, and forehead Functions: Thermoregulation Secretion of various substances Protection from microbes Figure 5.10 (b) © McGraw Hill (b) ©CNRI/Science Source; 40  Apocrine Sweat Glands Simple, coiled, tubular glands that secrete into hair follicles at the armpits (axillae), nipples (areola), groin (pubic region), and anus (anal region) Secretion is thick, cloudy, and composed of proteins and lipids Bacterial growth causes distinct odor in these regions Figure 5.10 (c) © McGraw Hill (c, d) ©McGraw-Hill Education/Alvin Telser, Ph.D., photographer 41  Sebaceous Glands Holocrine glands that secrete oily sebum into hair follicles or directly onto skin surface Lubrication; prevents drying of hair and skin Relatively inactive during childhood; sex hormones at puberty cause secretions to increase significantly Figure 5.10 (d) © McGraw Hill (c, d) ©McGraw-Hill Education/Alvin Telser, Ph.D., photographer 42  Other Integumentary Glands Ceruminous glands are apocrine glands located in external acoustic meatus Secretion mixes with sebum and keratinocytes to produce cerumen Cerumen helps trap particles and small insects, provides lubrication to eardrum, and contains antimicrobial lysozyme Mammary glands are found in the breasts Modified apocrine glands Functional in pregnant females in response to hormone signals, resulting in production of breast milk © McGraw Hill 43  Integument Repair and Regeneration Figure 5.11 © McGraw Hill 44  Aging of the Integument Skin repair takes longer Collagen content decreases; elasticity declines Immune responsiveness diminishes Skin becomes drier Number of melanocytes dereases; certain sun-exposed areas show dark spots Hair follicle output declines Vitamin D synthesis decreases UV radiation damages skin cell DNA © McGraw Hill 45  Skin Cancer 1 Skin cancer is the most common form of cancer Chronic sun exposure is predominant skin cancer risk factor Three main types of skin cancer: Basal cell carcinoma: most common, least dangerous Starts in stratum basale © McGraw Hill Dr. P. Marazzi/Science Photo Library/Getty Images 46  Skin Cancer 2 Squamous cell carcinoma: may metastasize Starts in stratum spinosum © McGraw Hill Science Photo Library/Alamy Stock Photo 47  Skin Cancer 3 Malignant melanoma: most deadly Starts from melanocytes (usually in a mole) © McGraw Hill Source: National Cancer Institute (NCI)/U.S. Department of Health and Human Services (USHSS) 48