Hole's Human Anatomy & Physiology Chapter 06 Lecture Outline PDF

Chapter 06 Lecture Outline...

Chapter 06 Lecture Outline See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. ©2019 McGraw-Hill Education. 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 Education.  Skin and Its Tissues Two or more types of tissues grouped together and performing specialized functions constitute an organ. Skin is the largest organ in body by weight. Skin is also called the cutaneous membrane. The skin and its accessory structures (hair, nails, glands, sensory receptors) make up the integumentary system. Composed of several tissue types. Contains 2 layers: epithelial tissue overlying connective tissue. Outer layer is the epidermis. Deeper layer is the dermis. ©McGraw-Hill Education  Figure 6.1 Skin and Its Epidermis: Tissues Outer layer. Stratified squamous epithelium. Basement membrane between epidermis and dermis. Dermis: Inner layer. Thicker of the 2 layers of the skin. Connective tissue. Contains collagenous and elastic Subcutaneous fibers. layer (hypodermis): Beneath dermis; insulating layer. Areolar and adipose connective tissue. ©McGraw-Hill Education © McGraw-Hill Education/Al Telser, photographer  Figure 6.2 Basic Structure of the Skin ©McGraw-Hill Education b: © McGraw-Hill Education/Al Telser, photographer  Epidermis Epidermis: Stratified squamous epithelium; rests on basement membrane Lacks blood vessels Deepest layer, stratum basale, nourished by blood vessels in dermis As cells grow, they migrate toward free surface, away from nutrient supply As they migrate, older cells, keratinocytes, begin to flatten and die. Keratinization: Process of hardening, dehydration, and keratin accumulation that occurs in epidermal cells as they migrate outward. Keratin: Tough, fibrous, waterproof protein made and stored in the cells As cells reach outer surface, become tightly packed, develop desmosomes, form outer layer, stratum corneum Stratum corneum cells are eventually shed from skin surface Thickest on palms and soles (0.8 through 1.4mm) Most of body has thinner epidermis, 0.07 through 0.12 mm. ©McGraw-Hill Education  Figure 6.3 Epidermis 5 Layers of Epidermis: Stratum corneum: outermost layer; dead, keratinized cells. Stratum lucidum: only in thick skin – palms, soles. Stratum granulosum. Stratum spinosum. Stratum basale/germinativum: deepest, mitotic layer. Functions of epidermis: Protects against water loss, harmful chemicals, mechanical injury, pathogens. ©McGraw-Hill Education  Table 6.1 Layers of the Epidermis Layer Location Characteristics Many layers of keratinized, dead Stratum corneum Outermost layer epithelial cells that are flattened and non- nucleated Between stratum Stratum lucidum corneum and stratum Cells appear clear; nuclei, organelles, and (only present in granulosum on soles cell membranes are no longer visible thick skin) and palms Three to five layers of flattened granular Stratum Beneath the stratum cells that contain shrunken fibers of granulosum corneum keratin and shriveled nuclei Many layers of cells with centrally Beneath the stratum Stratum spinosum located, large, oval nuclei and developing granulosum fibers of keratin; cells becoming flattened A single row of cuboidal or columnar cells Stratum basale Deepest layer that divide and grow; this layer also (basal cell layer) includes melanocytes ©McGraw-Hill Education  Figure 6.4 Epidermis: Melanocytes Melanocytes located in the stratum basale produce the dark pigment melanin Absorbs UV light from sunlight and provides skin color Melanin is distributed into keratinocytes, to protect skin cells from damaging effects of U V light (DNA damage, fibroblast damage, skin cancer). Access the long description slide. ©McGraw-Hill Education  Epidermis: Skin Color Factors Affecting Skin Color: Hereditary Factors: All people have same number of melanocytes, but vary in amount of melanin produced (this is under genetic control). Varying distribution and size of melanin granules. Albinos inherit mutation in melanin genes; lack melanin. Environmental Factors Sunlight. UV light from sunlamps. X-rays. Physiological Factors: Oxygenation in blood of dermal blood vessels: pinkish, cyanosis. Vasodilation/vasoconstriction of dermal blood vessels. Accumulation of carotene pigment from diet. Jaundice. ©McGraw-Hill Education  Clinical Application 6.1 Indoor Tanning and Skin Cancer Exposure to sunlight or a tanning bed causes melanocytes to produce more melanin, and skin darkens. Tanning bed uses doses of UV radiation that can overwhelm body’s natural protective responses against skin cancer. Basal cell carcinoma and squamous cell carcinoma arise from epithelial cells in skin. Melanomas arise from melanocytes. Melanomas are least common (4%) skin cancers, but cause 80% of skin cancer deaths. ©McGraw-Hill Education  Dermis 1 Dermis: Inner layer of skin. Average of 1 through 2 mm thick. Contains dermal papillae between epidermal ridges. Binds epidermis to underlying tissues. Connective tissue layer. Contains muscle fibers. Nerve cell processes. Dermal blood vessels supply Hair nutrients to all skin follicles, sweat & sebaceous glands. cells. Sensory receptors: Lamellated (Pacinian)corpuscles for pressure, Tactile (Meissner’s) corpuscles for light touch. ©McGraw-Hill Education  Dermis 2 The dermis consists of 2 layers: Papillary layer: Superficial layer. Areolar connective tissue. Thinner of the 2 layers. Location of dermal papillae. Reticular layer: Deeper layer. Dense irregular connective tissue. Thicker of 2 layers. ©McGraw-Hill Education  Accessory Structures of the Skin from the epidermis, Accessory structures originate extend into dermis or hypodermis Accessory structures of the skin: Hair follicles. Nails. Skin glands (sweat and sebaceous). If accessory structures remain intact, injured/burned dermis can regenerate. ©McGraw-Hill Education  Figure 6.6 Nails Nails: Protective coverings on ends of fingers and toes. 3 parts of a nail: Nail plate: overlies nail bed. Nail bed: surface of skin, under nail plate. Lunula: most active growing region; pale, half-moon-shaped region at base of nail plate. ©McGraw-Hill Education  Figure 6.7 Hair Follicles Hair is present on all surfaces of skin except palms, soles, lips, nipples, parts of external reproductive organs Hair follicle: Tube-like depression of epidermal cells from which hair develops; extends into dermis or the subcutaneous layer. 3 parts of hair: Hair bulb (dividing cells). Hair root. Hair shaft (dead, epidermal Hair papilla contains blood vessels cells). to nourish hair Hair color is due to type and amount of melanin Arrector pili muscle (goosebumps). ©McGraw-Hill Education b: © McGraw-Hill Education/Al Telser  Clinical Application 6.2 Hair Loss Most common type of baldness is pattern baldness; top of head loses hair (called androgenic alopecia) Associated with lowered level of testosterone (men) or estrogen (women) Progenitor cells are lacking in bald spots, but stem cells are present Alopecia areata: body produces antibodies that attack hair follicles; autoimmune hair loss. ©McGraw-Hill Education  Figure 6.9 Skin Glands: Sebaceous Glands Sebaceous Glands: Holocrine glands. Usually associated with hair follicles. Produce sebum, which consists of fatty material and cellular debris. Sebum keeps hair and skin soft and waterproof. Excess sebum can result in acne. Absent on palms and soles. ©McGraw-Hill Education © McGraw-Hill Education/Al Telser, photographer  Clinical Application 6.3 Acne Acne vulgaris is a disorder of sebaceous glands Common at puberty, because sebaceous glands are excessively responsive to androgens Sebaceous glands become clogged with extra sebum and epithelial cells Clogged glands provide good environment for anaerobic bacteria; infection results in inflammation Affects 80% of people between 11 and 30 years of age Treated best with Vitamin A derivatives, systemic antibiotics, salicylic acid, benzoyl peroxide. ©McGraw-Hill Education  Figure 6.10 Skin Glands: Sweat Glands: Sweat Glands Also called sudoriferous glands. Widespread in skin. Originate in deeper dermis or hypodermis as ball-shaped coils. Eccrine (merocrine) glands: Most numerous. Respond to elevated body temperature. Apocrine sweat glands: Axillary and groin areas. Secrete by exocytosis. Respond to emotions, pain. Ceruminous glands—ear wax Mammary glands—milk ©McGraw-Hill Education  Table 6.2 Skin Glands Type Description Function Location Sebaceous glands Groups of Keep hair soft, Near or connected to specialized pliable, waterproof hair follicles, epithelial cells everywhere but on palms and soles Merocrine sweat Abundant sweat Lower body Originate in deep glands glands with temperature dermis or odorless secretion subcutaneous layer and open to surface on forehead, neck, and back Apocrine sweat Less numerous Wet skin during Near hair follicles in glands sweat glands with pain, fear, armpit and groin secretions that emotional upset, develop odors and sexual arousal Ceruminous glands Modified sweat Secrete ear wax External acoustic glands meatus Mammary glands Modified sweat Secrete milk Breasts glands ©McGraw-Hill Education  Skin Functions Skin is versatile, and vital for homeostasis. Functions of the skin: Protective covering, barrier against harmful substances and microorganisms. Prevents some water loss. Contains sensory receptors. Excretes some wastes. Helps produce Vitamin D. Helps regulate body temperature. ©McGraw-Hill Education  Regulation of Body Temperature Important to regulate body temperature; slight shift can disrupt rates of metabolic reactions Set point is monitored by Hypothalamus Deep body temperature stays close to set point of 37 degrees Celsius or 98.6 degrees Fahrenheit Skin plays key role in homeostatic mechanisms that regulate body temperature. ©McGraw-Hill Education  Heat Production and Loss Heat is a product of cellular metabolism. The most active body cells are major heat producers: skeletal muscle, cardiac muscle, cells of the liver. When body is too warm, body responds with vasodilation of dermal blood vessels and vasoconstriction of deep blood vessels. Heat can escape through skin. Methods of heat loss: 1. Radiation: Primary method, infrared heat rays escape. 2. Conduction: Heat moves from skin to cooler objects. 3. Convection: Heat loss into circulating air currents. 4. Evaporation: Sweat changes into a gas, carries heat away. ©McGraw-Hill Education  Figure 6.12 Body Temperature Regulation When body temperature rises: Thermoreceptors signal hypothalamus. Vasodilation of dermal blood vessels. Sweat glands are activated. When body temperature falls: Thermoreceptors signal hypothalamus. Vasoconstriction of dermal blood vessels. Sweat glands are inactive. Muscles contract involuntarily (shivering). ©McGraw-Hill Education  Problems in Temperature Regulation Hyperthermia: abnormally high body temperature Can occur on hot, humid day, when sweat cannot evaporate. When air temperature is high, radiation is less effective. Body may gain heat from hotter air. Skin becomes dry, person gets weak, dizzy, nauseous, with headache, rapid pulse. Hypothermia: abnormally low body temperature Can result from prolonged exposure to cold, or illness. Shivering is involuntary skeletal muscle contraction, caused by hypothalamus. Progresses to confusion, lethargy, loss of reflexes and consciousness. Without treatment, organs shut down. ©McGraw-Hill Education  Clinical Application 6.4 Elevated Body Temperature Loss of ability of homeostatic temperature control mechanism to function in an extremely hot environment: Exposure to very high heat can overwhelm temperature control mechanisms, leading to hyperthermia. If body heat builds up faster than heat can be lost from body, body temperature will rise, even when set point is normal. Extreme vasodilation can collapse cardiovascular system; Fever: can be fatal. Set point is elevated by the immune system, to fight infection. Phagocytes release pyrogens in response to presence of bacteria, viruses; hypothalamus increases set point and raises body temperature. Elevated body temperature helps destroy pathogens. ©McGraw-Hill Education  Healing of Wounds and Burns Inflammation is a normal response to injury or stress Inflammation is body’s attempt to restrict spread of infection Blood vessels in affected tissues dilate and become more permeable, allowing fluids to leak into the damaged tissues Inflamed skin may become: Reddened. Swollen. Warm. Painful. ©McGraw-Hill Education  Cuts A shallow cut, which affects only the epidermis, results in epidermal cells along its margin dividing more rapidly than usual, to fill gap A deep cut, reaching dermis or subcutaneous layer, results in blood vessels breaking; released blood forms a clot Clot consists of fibrin, blood cells and platelets. Clot and dried tissue fluid form scab. Epithelial cells reproduce, fill in the wound. Fibroblasts secrete collagen fibers to bind wound together. Growth factors stimulate new tissue formation. Phagocytic cells remove dead cells and debris, scab sloughs off. Excess collagenous fibers may form elevated mass called a scar. ©McGraw-Hill Education  Figure 6.13 Healing of a Wound ©McGraw-Hill Education  Burns Burns are classified by extent of tissue damage: Superficial, partial-thickness (first degree) burn: Injures only epidermis, as in sunburn; redness, heat, inflammation. Healing takes days-weeks, no scarring. Deep, partial-thickness (second degree) burn: Destroys epidermis and some dermis, as in burn from hot liquid. May blister, healing varies with severity of burn & stem cell survival. Stem cells in hair follicles and glands can help regenerate skin. Full-thickness (third degree) burn: Destroys Usually recovers completely, epidermis, no scarring. dermis, accessory structures. Results from prolonged exposure to heat, flames, hot liquids. Some healing from margins. Often requires skin graft, skin substitutes. ©McGraw-Hill Education  Figure 6.15 Rule of Nines for Burn Patients Treatment of burn patients involves estimating extent of injured body surface. “Rule of Nines” divides body surface into regions of 9% or multiples of 9. From this estimate, plans to replace fluids, electrolytes, and skin can be figured. ©McGraw-Hill Education  Life-Span Changes Cell cycle slows, skin becomes scaly, age spots appear. Epidermis and dermis become thinner. Loss of fat in subcutaneous layer; person feels cold. Wrinkling, sagging of skin occur. Sebaceous glands secrete less oil; skin becomes dry. Melanin production slows; hair whitens. Hair thins. Number of hair follicles decreases. Nail growth becomes impaired. Sensory receptors decline. Body temperature regulation becomes less effective. Diminished ability to produce Vitamin D. ©McGraw-Hill Education