Integumentary System Chapter 6 PDF

INTEGUMENTARY SYSTEM Chapter 6 Spring 2023 HUMAN ANATOMY & PHYSIOLOGY I – BIO 103 6.1 Layers of the Skin 1 Two or more types of tissues grouped together and performing specialized functions constitute an organ. The skin and its accessory structures (hair, nails, glands, sensor...

INTEGUMENTARY SYSTEM Chapter 6 Spring 2023 HUMAN ANATOMY & PHYSIOLOGY I – BIO 103 6.1 Layers of the Skin 1 Two or more types of tissues grouped together and performing specialized functions constitute an organ. The skin and its accessory structures (hair, nails, glands, sensory receptors) make up the integumentary system. The skin: ◦ Largest organ by weight ◦ Composed of several tissue types ◦ Also called the cutaneous membrane ◦ Contains 2 layers: epithelial tissue overlying connective tissue ◦ Epidermis: Outer layer ◦ Dermis: Inner layer 2 6.1 Layers of the Skin 2 Epidermis: Outer layer, composed of stratified squamous epithelium Basement membrane between epidermis and dermis Dermis: Inner layer, thicker than epidermis Connective tissue, with collagenous and elastic fibers, muscle, blood, nervous tissue Subcutaneous layer (hypodermis): Beneath dermis; insulating layer Areolar and adipose connective tissue. Not considered part of the skin Contains blood vessels that supply skin 3 Figure 6.1 Skin Is Composed of Several Tissues Al Telser/McGraw-Hill Education 4  Figure 6.2 Skin and Subcutaneous Layer ©McGraw-Hill Education b: © McGraw-Hill Education/Al Telser, photographer Epidermis Stratified squamous epithelium 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 outermost layer, stratum corneum Stratum corneum cells are eventually shed from skin surface Thickest on palms and soles (0.8 through 1.4 mm) Most of body has thinner epidermis, 0.07 through 0.12 mm Functions: Protects against water loss, harmful chemicals, 6  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 The first Stratum lucidum column Between stratumshows Layer, the second corneum and stratum Cells appear clear; nuclei, organelles, and (only presentcolumn showsonLocation, cell and the third in granulosum soles membranes are no longer visible thick skin) column and shows palms Characteristics. 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 8 Special Cells of the Epidermis Dendritic (Langerhans) Cells: Found in the stratum spinosum Phagocytes; protect skin and underlying tissues from infection Tactile (Merkel) Cells: Found in stratum basale Along with sensory nerve endings, for Tactile Discs in dermis Act as sensory receptors for light touch Melanocytes: Found in stratum basale Produce the pigment melanin ◦ Eumelanin: Brownish-black pigment of epidermis ◦ Pheomelanin: Reddish yellow pigment, found in certain areas Absorbs UV light from sunlight and provides skin color Melanin is distributed to keratinocytes, to protect from UV radiation (DNA damage, fibroblast damage, skin cancer) 9  Epidermis: Melanocytes 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. Albinism: inherited 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 12  Dermis 1 Inner layer of skin Average of 1 to 2 mm thick Contains projections called dermal papillae between epidermal ridges Binds epidermis to underlying tissues Connective tissue layer, containing muscle fibers, nerve cell processes Dermal blood vessels supply nutrients to all skin cells Contains hair follicles, sweat and sebaceous glands Contains sensory receptors: Lamellated (Pacinian) ©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, which form fingerprints Reticular layer: Deeper layer Dense irregular connective tissue ©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  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  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 Parts of hair: Hair root: Extends from skin surface to dermis or hypodermis Hair bulb: Deepest part of hair root; contains dividing cells of hair matrix Hair shaft: Portion of hair that extend beyond skin surface; composed of dead, epidermal cells Hair papilla contains blood vessels to nourish hair Hair color is due to type and amount of melanin ©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 18  Figure 6.9 Skin Glands: Sebaceous Sebaceous Glands: 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 20  Skin Glands: Sweat Glands Sweat (Sudoriferous) Glands: Widespread in skin Originate in deeper dermis or hypodermis as ball-shaped coils Types of sweat glands: Eccrine (merocrine) glands: Most numerous, consist mainly of water, some salts, wastes Respond to elevated body temperature Open to body surface through pores Apocrine sweat glands: Axillary and groin areas; open into hair follicles Called apocrine, but secrete by exocytosis Respond to emotions, pain Specialized sweat glands: Ceruminous glands—ear wax Mammary glands—milk ©McGraw-Hill Education ©McGraw-Hill Education Table 6.2 Glands of the Skin 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 Thefirst column glands with shows Type, temperaturethe second dermis or column shows odorless Description, the third column secretion subcutaneous layer shows Function, and the fourth column and open to surface on forehead, neck, shows Location. 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 23 6.3 Skin Functions Skin is versatile, and vital for homeostasis Functions of the skin: ◦ Protective barrier: Protects against harmful substances, UV radiation, microorganisms, water loss ◦ Sensation: Contains sensory receptors for touch, pressure, temperature changes, pain ◦ Excretion of some wastes ◦ Production of Vitamin D: Starts in skin; when produced and activated, helps with calcium absorption ◦ Regulation of body temperature: Helps cool body by sweating and blood flow changes 24 Heat Production and Loss Important to regulate body temperature; slight shift can disrupt rates of metabolic reactions Set point is monitored by hypothalamus in brain 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 Heat is product of cellular metabolism; mainly produced by most active cells (liver, skeletal and cardiac muscle) 25  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  Body Temperature Regulation When body temperature rises: Thermoreceptors signal hypothalamus Vasodilation of dermal blood vessels Vasoconstriction of deep blood vessels Sweat glands are activated When body temperature falls: Thermoreceptors signal hypothalamus Vasoconstriction of dermal blood vessels Vasodilation of deep 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 28 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; can be fatal Fever: 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 29  Healing of Wounds and Burns Inflammation: A normal response to injury or stress 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 31  Figure 6.14 Healing of a Wound ©McGraw-Hill Education  Burns 1 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 to 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 and stem cell survival Stem cells in hair follicles and glands can help regenerate skin Usually recovers completely, no scarring Full-thickness (third degree) burn: Destroys epidermis, dermis, accessory structures Results from prolonged exposure to heat, flames, hot liquids Some healing from margins Often requires skin graft, skin substitutes 33  Figure 6.16 Rule of Nines for Burn Patients Rule of Nines: Divides body surface into regions of 9% or multiples of 9 Used to estimate extent of injured body surface from a burn for treatment 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 35