HOLE'S Essentials of Human Anatomy & Physiology Chapter 6 PDF

Because learning changes everything.® Chapter 06 Integumentary System HOLE’S ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY Fifteenth Edition Charles J. Welsh and Cynthia Prentice-Craver © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written cons...

Because learning changes everything.® Chapter 06 Integumentary System HOLE’S ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY Fifteenth Edition Charles J. Welsh and Cynthia Prentice-Craver © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  6.1: Introduction to the Integumentary System Organ: a body structure composed of two or more different tissue types that perform specific functions Skin is the largest organ in the body by weight Accessory structures of the skin: hair, nails, glands, and sensory receptors The skin and its accessory organs make up the integumentary system Skin acts as a barrier between internal environment and the external environment © McGraw Hill, LLC 2  6.2: Skin and Its Tissues Skin consists of 2 major layers: Epidermis: thin, outer layer of stratified squamous epithelium Dermis: thicker, inner layer of connective tissue, blood vessels, smooth muscle, and nervous tissue Basement membrane separates epidermis from dermis, and anchors these layers together Subcutaneous layer (hypodermis): Layer underneath dermis, consisting of areolar and adipose tissues Binds skin to underlying tissues, but is not part of the skin Adipose tissue insulates to conserve body heat Contains major blood vessels that supply the skin © McGraw Hill, LLC 3  Figure 6.1: The Layers of the Skin and Hypodermis (b): Al Telser/McGraw Hill Access the text alternative for these images © McGraw Hill, LLC 4  The Epidermis 1 Characteristics of the epidermis: Consists of stratified squamous epithelium Lacks blood vessels Consists of 4 layers in most areas, 5 layers in thick skin Stratum basale (or stratum germinativum) is the deepest layer; it consists of dividing cells; it is well-nourished by dermal blood vessels As basal cells divide, older cells, called keratinocytes (due to accumulation of fibrous protein, keratin), migrate toward skin surface As keratinocytes migrate outward, they harden, dehydrate, and die, in a process called keratinization © McGraw Hill, LLC 5  The Epidermis 2 The epidermis is important because it protects against water loss, mechanical injury, chemicals, and microorganisms. These 4 layers of the epidermis are found in all areas of the body: Stratum basale: innermost layer, dividing layer Stratum spinosum Stratum granulosum Stratum corneum: outermost layer; dead, flattened, keratinized cells; these are continually being shed from the outer skin surface This layer is found only in the thick skin of the palms and soles: Stratum lucidum: layer between the stratum granulosum and the stratum corneum © McGraw Hill, LLC 6  Figure 6.2: The Epidermis of Thick Skin (b): Al Telser/McGraw-Hill Access the text alternative for these images © McGraw Hill, LLC 7  The Epidermis 3 Melanocytes: Special cells that produce the pigment, melanin Found in deepest layer of epidermis and in dermis Melanin protects DNA of skin cells against damaging effects of UV radiation from the sun Melanin granules shade the nucleus of a cell from UV radiation to prevent mutation in the DNA Melanin pigment provides skin and hair color; the more melanin is present, the darker the skin or hair will be Melanin is transferred from extensions of the melanocytes to other nearby cells by the process of cytocrine secretion Eumelanin is brownish-black, and pheomelanin (found in areas such as the lips) is reddish-yellow © McGraw Hill, LLC 8  Figure 6.3: Melanocytes and Melanin Pigment (a): Don W. Fawcett/Science Source Access the text alternative for these images © McGraw Hill, LLC 9  Skin Color 1 All people have about the same number of melanocytes Skin color is genetically determined, and involves the amount of melanin that the melanocytes produce and the size and distribution of melanin granules Skin color results from a combination of genetic, environmental, and physiological factors Exposure to sunlight, UV light from sun lamps, and X-rays cause darkening of skin, due to an increase in melanin production © McGraw Hill, LLC 10  Skin Color 2 Circulation within dermal blood vessels affects skin color: Oxygen-rich blood has a bright red color, due to hemoglobin; causes skin of light-skinned people to look pinkish Oxygen-poor blood has a deep red tone; causes skin of light- skinned people to appear bluish, which is called cyanosis Diet and disease also affect skin color: Yellowish skin color can come from eating too many orange or yellow foods with carotene Bright yellow color in the skin can be caused by jaundice due to liver disease © McGraw Hill, LLC 11  The Dermis The dermis: Binds the epidermis to underlying tissues Border between epidermis and dermis is uneven, due to epidermal ridges (which extend down toward dermis) and dermal papillae (which extend upward toward epidermis) Genetically determined pattern of friction ridges formed by dermal papillae provide for unique fingerprints The dermis consists of areolar and dense connective tissue, with collagen and elastic fibers within a gel-like ground substance The fibers provide toughness and elasticity to skin Dermal blood vessels carry nutrients to upper layers of skin, and also help regulate body temperature The dermis also contains nerve fibers, sensory receptors, hair follicles, sebaceous glands, and sweat glands © McGraw Hill, LLC 12  6.3: Accessory Structures of the Skin: Epidermal Derivatives Nails: Protective coverings over the ends of fingers and toes Consist of a nail plate overlying a layer of skin surface, called the nail bed Lunula: half-moon-shaped structure at base of nail plate; visible portion of nail matrix, the most actively growing region of the nail As new cells are produced, older ones are pushed outward and become keratinized, just as in other parts of the skin Keratin of nails is harder than that of the stratum corneum of the rest of the skin Nail appearance is affected by genetics, injury, nutritional deficiencies, disease and aging, and can be used in medical diagnosis. © McGraw Hill, LLC 13  Figure 6.4: Longitudinal and Dorsal Views of a Nail Access the text alternative for these images © McGraw Hill, LLC 14  Hair and Hair Follicles Hair can be found in nearly all regions of the skin except palms, soles, lips, nipples, and portions of external genitalia Each hair develops from epithelial stem cells at the base of a tube-like depression called the hair follicle Hair follicles dip down into the dermis or sometimes the subcutaneous layer The deepest part of the hair root is called the hair bulb; it is located at the base of the hair follicle Hair matrix lies within the hair bulb; matrix is composed of epithelial cells nourished by dermal blood vessels in the hair papilla at the base of the hair bulb As new cells are formed in the bulb, old cells are pushed outward and become keratinized, and die, forming the hair shaft Hair is composed of dead, keratinized epithelial cells © McGraw Hill, LLC 15  Figure 6.5: Hair Follicles (b, c): Al Telser/McGraw Hill Access the text alternative for these images © McGraw Hill, LLC 16  Figure 6.6: Hair Emerging from a Hair Follicle CNRI/SPL/Science Source Access the text alternative for these images © McGraw Hill, LLC 17  Hair Color and Properties Hair color is determined by genetics, which determine type and amount of melanin produced by epidermal melanocytes Melanin produced by melanocytes is responsible for most hair colors Dark hair contains eumelanin (brownish-black), while blonde and red hair contain more pheomelanin (reddish-yellow) Genetic lack of melanin, or older age, causes albinism (white) Mixture of pigmented and unpigmented hair is gray A bundle of smooth muscle cells, called an arrector pili muscle, attaches to each hair follicle; when it contracts in response to cold temperature or emotional upset, it causes goose bumps © McGraw Hill, LLC 18  Skin Glands Sebaceous glands: Secrete an oily substance called sebum, that waterproofs and softens the hair and skin Holocrine glands; entire cells filled with secretion are released Associated with hair follicles Sweat (sudoriferous) glands: Merocrine glands; secretions exit cells via exocytosis 2 types of sweat glands: Eccrine: merocrine glands that respond to body temperature; more abundant type; many found on forehead, neck, back; secrete onto skin surface Apocrine: merocrine glands (incorrectly named) which become active at puberty; respond to fear, emotional upset, pain, or sexual arousal; most numerous in axilla and groin; sweat contains proteins & fats that produce body odor; secrete into hair follicles © McGraw Hill, LLC 19  Figure 6.7: Sebaceous Glands Secrete into Hair Follicles Alvin Telser/McGraw Hill Access the text alternative for these images © McGraw Hill, LLC 20  Modified Sweat Glands Ceruminous glands: secrete wax in the ear canal, to trap dust and pathogens Mammary glands: secrete milk to nourish a baby © McGraw Hill, LLC 21  6.4: Skin Functions Functions of the skin: Important for maintaining homeostasis Protective covering; prevents many substances and pathogenic microorganisms from entering body and protects underlying tissues Waterproof; slows down water loss by diffusion Melanin pigment protects against UV radiation from the sun Houses sensory receptors for touch, pressure, pain, temperature Excrete wastes Conducts some chemical reactions in the synthesis of vitamin D; vital for bone and tooth development Body temperature regulation, via sweat gland activation, and vasodilation or vasoconstriction of dermal blood vessels Synthesizes certain biochemicals © McGraw Hill, LLC 22  Role of Skin in Body Temperature Regulation Proper temperature regulation is vital to maintaining optimal metabolic reaction rates The skin plays a major role in temperature regulation, with the hypothalamus controlling the process Active cells, such as those of the heart and skeletal muscle, and the liver, produce heat Heat may be lost to the surroundings from the skin through radiation and the evaporation of sweat © McGraw Hill, LLC 23  Skin’s Response to Body Temperature Changes Responses to excess heat (hyperthermia): Vasodilation of dermal blood vessels; more blood enters skin and is released from the body Sweat glands are activated; as sweat is released, it evaporates, cooling the skin Responses to excess cooling (hypothermia): Vasoconstriction of dermal blood vessels, keeping blood in core Inactivation of the sweat glands Shivering, an involuntary form of skeletal muscle contraction, which causes an increase in cellular respiration; this releases heat as a byproduct © McGraw Hill, LLC 24  Healing of Wounds Inflammation, in which blood vessels dilate and become more permeable, causing tissues to become red and swollen, is the body's normal response to injury or stress Dilated blood vessels bring in fluids, oxygen, nutrients, and immune cells to aid in healing Superficial cuts are filled in by reproducing epithelial cells Deeper injuries, extending into the dermis or subcutaneous layer, require a more extensive response © McGraw Hill, LLC 25  The Characteristics of Inflammation TABLE 6.1 Inflammation Symptom Cause Redness Vasodilation, more blood in area Heat Large amount of blood accumulating in area and as a by-product of increased metabolic activity in tissue Swelling Increased permeability of blood vessels, fluids leaving blood go into tissue spaces (edema) Pain Injury to neurons and increased pressure from edema © McGraw Hill, LLC 26  The Healing of a Deep Wound 1 The response to a deep injury, extending into the dermis or subcutaneous layer: Involves the formation of a blood clot from the released blood The blood clot and dried tissue fluids form a scab to cover the wound Fibroblasts migrate into the area, and secrete collagen fibers to bind the edges of the wound together Phagocytic cells remove debris and dead cells Damaged tissue is replaced and the scab sloughs off © McGraw Hill, LLC 27  The Healing of a Deep Wound 2 Extensive collagen fiber production in the area may form an elevated area called a scar Large wounds leave scars and healing may be accompanied by the formation of rounded masses called granulations: A new branch of a blood vessel grows into the area The vessel is accompanied by a cluster of fibroblasts that begin producing collagen fibers and repairing the wound Eventually, blood vessels are resorbed and the fibroblasts leave, which leaves a scar of collagen fibers. © McGraw Hill, LLC 28  Figure 6.8: Stages in Wound Healing Access the text alternative for these images © McGraw Hill, LLC 29  Common Skin Disorders 1 Disorder Description Disorder Description acne (AK-nee) Disease of the sebaceous keloid (KEY-loyd) Elevated, enlarging fibrous scar glands that produces usually initiated by an injury blackheads and pimples alopecia (al-oh- Hair loss, usually sudden mole (mohl) Benign skin tumor (nevus) that is PEE-shah) usually pigmented; colors range from brown to black athlete’s foot Fungus (Tinea pedis) Pediculosis (peh- Disease produced by an (ATH-leetz foot) infection usually in the skin dik-yoo-LOH-sis) infestation of lice of the toes and soles birthmark Congenital blemish or spot pruritus (proo- Itching of the skin (BERTH-mark) on the skin, visible at birth RYE-tus) or soon after boil (boyl) Bacterial infection psoriasis (so- Chronic skin disease (furuncle) of the skin, RYE-ah-sis) characterized by red patches produced when bacteria covered with silvery scales enter a hair follicle © McGraw Hill, LLC 30  Common Skin Disorders 2 Disorder Description Disorder Description carbuncle (KAR Bacterial infection, similar to a boil, that pustule (PUS Elevated, pus-filled area on the bunk-ul) spreads into the subcutaneous tissues tyul) skin cyst (sist) Liquid-filled sac or capsule scabies (SKAY Disease resulting from an beez) infestation of mites dermatitis (der Inflammation of the skin seborrhea (seb Hyperactivity of the sebaceous mah-TIE-tis) oh-REE-ah) glands, causing greasy skin and dandruff eczema (EK-zeh Noncontagious skin rash that produces ulcer (UL-ser) Open sore mah) itching, blistering, and scaling erythema (er-ih Reddening of the skin due to dilation of urticaria (ur-tee Allergic reaction of the skin that THEE-mah) dermal blood vessels in response to injury KARE-ee-ah) produces reddish, elevated or inflammation patches (hives) herpes (HER Infectious disease of the skin, caused by vitiligo (VIT-ih Loss of melanocytes in parts of peez) the herpes simplex virus and characterized LEE-goh) the epidermis, producing by recurring formations of small clusters of whitened areas of skin vesicles impetigo (im Contagious disease of bacterial origin, wart (wort) Flesh-colored, raised area caused peh-TIE-go) characterized by pustules that rupture and by a viral infection become covered with loosely held crusts © McGraw Hill, LLC 31  Because learning changes everything. ® www.mheducation.com © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.