Shier_Holes_HumanA&P_16e_Chap006_PPT_JB_Accessible.pptx

Because learning changes everything. ® Chapter 06 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hil...

Because learning changes everything. ® Chapter 06 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 6.1 Layers of the Skin 1 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 3 Figure 6.1 Skin Is Composed of Several Tissues Al Telser/McGraw-Hill Education Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 4  Figure 6.2 Skin and Subcutaneous Layer **Use the Visible Body Atlas Software (Microanatomy) to show a 3D structure of the skin (b): Al Telser/McGraw-Hill Education Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 5 Epidermis 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, mechanical injury, pathogens Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 6 Figure 6.3 Epidermis of Thick Skin (b): Al Telser/McGraw-Hill Education Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 7 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 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) Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 8 Skin Color 1 Skin color results mainly from melanin pigment: Other 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 9 Skin Color 2 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 10 Dermis Dermis: 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) corpuscles for pressure, Tactile (Meissner’s) corpuscles for light touch Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 11 Layers of the Dermis 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 Thicker of 2 layers Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 12 Figure 6.2a Dermis Lies Deep to Epidermis Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 13 6.2 Accessory Structures of the Skin Accessory structures originate from the epidermis, 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 14 Nails Nails: Protective coverings on ends of fingers and toes 3 parts of a nail: Nail plate (body): Visible portion, keratinized cells, overlies nail bed Nail bed: Surface of skin, under nail plate Nail matrix: Active growth region, not visible, at proximal end of nail bed Lunula: Pale, half-moon-shaped region that lies over nail matrix; nail matrix conceals deeper blood vessels Cuticle: Fold at proximal end of nail; part of stratum corneum that extends slightly over nail Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 15 Figure 6.7 Nails Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 16 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 Arrector pili muscle: Attached to hair follicle; contracts in response to cold or fear, and causes goosebumps Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 17 Figure 6.8 Hair Follicles (b): Al Telser/McGraw-Hill Education Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 18 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 19 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 20 Figures 6.11 and 6.12 Skin Glands: Sweat Glands Astrid and Hanns-Frieder Michler/ SPL/Science Source Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 21 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 22 Heat Loss Through the Skin Methods of heat loss through the skin: Radiation: Primary method, infrared heat rays travel from warmer skin to cooler environment Conduction: Heat moves from warmer skin to cooler objects it is in contact with Convection: Heat loss from skin into circulating air currents Evaporation: Heat is lost through sweat as it evaporates, and carries heat away from the skin Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 23 Body Temperature Regulation Mechanisms 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) Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 24 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 25 6.4 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 26 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 27 Figure 6.14 Healing of a Wound Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 28 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 29 Burns 2 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 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 30 Figure 6.16 Rule of Nines for Burn Patients Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 31 6.5 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 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 32