Fig. 6.1 Hairs Sweat pores Dermal papilla Epidermis Tactile corpuscle Copyright © McGraw-Hill Education. Permission required for reproduction or display. Hairs Sweat pores Dermal papilla Epidermis Tactile corpuscle (touch receptor) Blood capillaries Hair follicle Dermis Sebaceous gland Hair receptor Apocrine sweat gland Hypodermis (subcutaneous fat) Hair bulb Sensory nerve fibers Merocrine sweat gland Piloerector muscle Cutaneous blood vessels Lamellar (pacinian) corpuscle (pressure receptor) Motor nerve fibers

Fig. 6.3 2 Sweat pore Stratum corneum Exfoliating Stratum lucidum Copyright © McGraw-Hill Education. Permission required for reproduction or display. Sweat pore Stratum corneum Exfoliating keratinocytes Stratum lucidum Stratum granulosum Dead keratinocytes Sweat duct Living keratinocytes Dendritic cell Stratum spinosum Tactile cell Melanocyte Stem cell Stratum basale Dermal papilla Tactile nerve fiber Dermis Dermal blood vessels 2

Fig. 6.5 3 (b) Papillary layer of dermis (a) Copyright © McGraw-Hill Education. Permission required for reproduction or display. (b) Papillary layer of dermis (a) (c) Reticular layer of dermis a: © McGraw­Hill Education/Dennis Strete; b: © Dr. Richard Kessel & Dr. Randy K./Visuals Unlimited/Corbis; c: © Dr. Kessel & Dr. Kardon/Tissues and Organs/Visuals Unlimited, Inc 3

Table 6.1 4

Fig. 6.6 5 Stratum corneum Epidermis Melanized cells of stratum basale Copyright © McGraw-Hill Education. Permission required for reproduction or display. Stratum corneum Epidermis Melanized cells of stratum basale Dermis (a) Dark skin (b) Light skin Top left: © Tom & Dee Ann McCarthy/Corbis; Top right: © Creatas/PunchStock RF; a-b: © McGraw­Hill Education/Dennis Strete 5

Fig. 6.7 6 Connective tissue root sheath Hair shaft Epithelial root Copyright © McGraw-Hill Education. Permission required for reproduction or display. Connective tissue root sheath Hair shaft Epithelial root sheath Hair medulla Sebaceous gland Piloerector muscle Hair cortex Hair receptor Bulge Hair root Hair matrix Hair bulb Apocrine sweat gland Dermal papilla Blood Capillaries in dermal papilla (a) (b) 0.5 µm b: ©CBS/Phototake 6

Fig. 6.9 7 Telogen Old club hair Epidermis Sebaceous gland Club hair Copyright © McGraw-Hill Education. Permission required for reproduction or display. Old club hair Epidermis Sebaceous gland Club hair (detached from matrix) Piloerector New hair Club Bulge Hair matrix Hair bulb Degeneration of lower follicle Dermis Dermal papilla 1 Anagen (early) Anagen (mature) 2 Catagen 3 Telogen (Growing phase, 6–8 years) Stem cells multiply and follicle grows deeper into dermis; hair matrix cells multiply and keratinize, causing hair to grow upward; old club hair may persist temporarily alongside newly growing hair. (Degenerative phase, 2–3 weeks) Hair growth ceases; hair bulb keratinizes and forms club hair; lower follicle degenerates. (Resting phase, 1–3 months) Dermal papilla has ascended to level of bulge; club hair falls out, usually in telogen or next anagen. 7

Fig. 6.10 8 Free edge Nail body Nail groove Nail fold Lunule Copyright © McGraw-Hill Education. Permission required for reproduction or display. Free edge Nail body Nail groove Nail fold Lunule Eponychium (cuticle) Eponychium Nail plate Nail fold Free edge Nail body Nail root Nail bed Nail matrix 8

a–c: © McGraw-Hill Education/Dennis Strete Fig. 6.11 Copyright © McGraw-Hill Education. Permission required for reproduction or display. Lumen Secretory cells Myoepithelial cells Lumen Secretory cells (a) Apocrine gland (b) Merocrine gland Gland Hair follicle (c) Sebaceous gland a–c: © McGraw-Hill Education/Dennis Strete 9

Table 6.2 10

Page 198 Copyright © McGraw-Hill Education. Permission required for reproduction or display. All SYSTEMS Skin covers the body and provides a barrier to pathogens and to excessive water loss; epidermal keratinocytes initiate synthesis of calcitriol, with effects on multiple other organ systems as noted. SKELETAL SYSTEM Bone growth and maintenance depend on calcium, which is absorbed from the diet under the influence of calcitriol. LYMPHATIC/ IMMUNE SYSTEM Dendritic cells of the skin alert the immune system when pathogens breach the epidermal barrier. MUSCULAR SYSTEM Muscle contraction depends on calcium, which is absorbed from the diet under the influence of calcitriol. RESPIRATORY SYSTEM Nasal guard hairs block some airborne debris from being inhaled; calcium is required for the secretion of respiratory mucus, which therefore depends on calcitriol. NERVOUS SYSTEM The transmission of nerve signals across synapses depends on calcium, which is absorbed from the diet under the influence of calcitriol. URINARY SYSTEM Skin complements the urinary system by excreting salts and some nitrogenous waste in the sweat; calcitriol promotes reabsorption of calcium by the kidneys. ENDOCRINE SYSTEM Hormone secretion depends on calcium as a trigger for exocytosis and, therefore, on calcitriol; the role of epidermal keratinocytes in synthesizing calcitriol is itself an endocrine function. DIGESTIVE SYSTEM By their role in calcitriol synthesis, keratinocytes influence intestinal absorption of calcium; calcium is needed for the secretion of all digestive enzymes and mucus. REPRODUCTIVE SYSTEM Cutaneous nerve endings are important in sexual stimulation; mammary glands produce milk; apocrine sweat glands secrete pheromones that affect sexual behavior and physiology; skin stretches to accommodate abdominal growth in pregnancy. CIRCULATORY SYSTEM The skin is a major blood reservoir; cutaneous vasoconstriction diverts blood to other organs; skin supports blood volume by retarding fluid loss; dermal vasoconstriction and vasodilation help to regulate blood temperature. 11