Mosby items and derived items © 2007, 2003 by Mosby, Inc.Slide 1 Chapter 6 Skin and Its Appendages

Mosby items and derived items © 2007, 2003 by Mosby, Inc.

Slide 3 Introduction Skin (integument) - body’s largest organ Skin (integument) - body’s largest organ Approximately 1.6 to 1.9 m 2 in average-sized adult Approximately 1.6 to 1.9 m 2 in average-sized adult Integumentary system -skin and its appendages—the hair, nails, and skin glands Integumentary system -skin and its appendages—the hair, nails, and skin glands

Slide 4 Structure of the Skin Cutaneous membrane Cutaneous membrane Two primary layers—epidermis and dermis; joined by dermal-epidermal junction Two primary layers—epidermis and dermis; joined by dermal-epidermal junction Hypodermis beneath dermis Hypodermis beneath dermis

Slide 5 Structure of the Skin Thin and thick skin Thin and thick skin  “Thin skin”—covers most of body surface (1 to 3 mm thick)  “Thick skin”—soles and palms (4 to 5 mm thick)

Slide 6 Structure of the Skin Epidermis Epidermis  Cell types Keratinocytes Keratinocytes Melanocytes Melanocytes Langerhans cells Langerhans cells

Slide 7 Structure of the Skin  Epidermis - made of 5 layers (strata) from inside out: Stratum germinativum (growth layer)—Made of stratum basale and stratum spinosum Stratum germinativum (growth layer)—Made of stratum basale and stratum spinosum  Stratum basale (base layer)—single layer of columnar cells - divide mitotically  Stratum spinosum (spiny layer)— –support

Slide 8 Structure of the Skin  Epidermis layers Stratum granulosum Stratum granulosum  lysosomal Stratum lucidum Stratum lucidum  cells filled with what will become keratin Stratum corneum Stratum corneum  most superficial layer;  dead cells filled with keratin (barrier area)

Slide 9 Epidermal growth and repair regeneration time - every 35 days regeneration time - every 35 days -callus formation - formed when an area receives a lot of friction -callus formation - formed when an area receives a lot of friction - -mitosis - 10% of cells in stratum basale enter mitosis on a daily basis. - -mitosis - 10% of cells in stratum basale enter mitosis on a daily basis.

Slide 10 Structure of the Skin Dermal-epidermal junction Dermal-epidermal junction  the epidermis glued to dermis below  partial barrier

Slide 11 Structure of the Skin Dermis Dermis  “true skin”—thicker than epidermis  Storage of water and electrolytes  Structures Arrector pili muscles/hair follicles Arrector pili muscles/hair follicles Sensory receptors Sensory receptors Sweat/sebaceous glands Sweat/sebaceous glands Blood vessels Blood vessels

Slide 12 Structure of the Skin Dermis Layers Dermis Layers Papillary layer Papillary layer  Composed of dermal papillae  Contains collagenous and elastic fibers  Contains dermal-epidermal junction  Forms fingerprints Reticular layer Reticular layer  Contains collagenous fibers, elastic fibers - makes skin tough but stretchable.

Slide 13 Dermis Dermal growth and repair Dermal growth and repair Dermis does not shed constantly Dermis does not shed constantly During wound healing fibroblasts form scars During wound healing fibroblasts form scars

Slide 14 Hypodermis (Subcutaneous layer)  Deep to the dermis  between the skin and other structures  Not actually part of the skin

Slide 15 Skin Color Melanin Melanin  Responsible for skin color - quantity, type, and distribution of melanin  Produced by melanocytes  Albinism—absence of melanin  Process regulated by enzymes, exposure to sunlight (UV radiation), certain hormones

Slide 16 Skin Color Other pigments Other pigments  Beta carotene  Hemoglobin Redder skin color when blood flow to skin increases Redder skin color when blood flow to skin increases Cyanosis - bluish color caused by loss of oxygen Cyanosis - bluish color caused by loss of oxygen Bruising - internal bleeding Bruising - internal bleeding

Slide 17 Functions of the Skin Protection Surface film Protection Surface film Protective barrier -mixing of sweat and oil with epithelial cells from skin surface Protective barrier -mixing of sweat and oil with epithelial cells from skin surface  Physical barrier to microorganisms  Barrier to chemical hazards  Reduces potential for mechanical trauma  Prevents dehydration  Protects (via melanin) excess UV exposure

Slide 18 Functions of the Skin Sensation Sensation  Somatic (skin) sensory receptors detect Pressure - Paccinian corpuscles Pressure - Paccinian corpuscles Touch - Meissner’s corpuscles Touch - Meissner’s corpuscles Temperature - Organs of Ruffini and Krause bulbs Temperature - Organs of Ruffini and Krause bulbs Pain - nerve endings. Pain - nerve endings.

Slide 19 Functions of the Skin Flexibility Flexibility  Skin is supple and elastic, thus permitting change in body contours without injury Excretion Excretion  Water  Urea/ammonia/uric acid

Slide 20 Functions of the Skin Hormone (Vitamin D) production Hormone (Vitamin D) production  Exposure of skin to UV light converts chemicals to precursor to vitamin D  Blood transports precursor to liver and kidneys, where vitamin D is produced

Slide 21 Functions of the Skin Immunity Immunity  Phagocytic cells destroy bacteria  Langerhans cells trigger helpful immune reaction working with “helper T cells”

Slide 22 Functions of the Skin Homeostasis of body temperatures Homeostasis of body temperatures  heat production must equal heat loss; skin plays a critical role in this process  Heat production By metabolism of foods in skeletal muscles and liver By metabolism of foods in skeletal muscles and liver Chief determinant of heat production is the amount of muscular work being performed Chief determinant of heat production is the amount of muscular work being performed

Slide 23 Functions of the Skin  Homeostatic regulation of heat loss negative feedback loop negative feedback loop Receptors in the hypothalamus monitor the body’s internal temperature Receptors in the hypothalamus monitor the body’s internal temperature If the body temperature is increased, the hypothalamus sends a nervous signal to the sweat glands and blood vessels of the skin If the body temperature is increased, the hypothalamus sends a nervous signal to the sweat glands and blood vessels of the skin The hypothalamus continues to act until the body’s temperature returns to normal The hypothalamus continues to act until the body’s temperature returns to normal

Slide 24 Appendages of the Skin Hair Hair  Development of hair Distribution Distribution lanugo lanugo terminal hair terminal hair  Development of hair Hair follicles and hair develop from epidermis Hair follicles and hair develop from epidermis Papilla Papilla Root Root Shaft Shaft Medulla Medulla

Slide 25 Appendages of the Skin  Appearance of hair Color Color Growth Growth Sebaceous glands Sebaceous glands Male pattern baldness -genetic tendency and male sex hormones Male pattern baldness -genetic tendency and male sex hormones

Slide 26 Appendages of the Skin Nails (Figure 6-17) Nails (Figure 6-17)  Consist of epidermal cells converted to hard keratin  Nail body—visible part of each nail  Root—part of nail in groove hidden by fold of skin, the cuticle  Lunula—moon-shaped white area nearest root  Nail bed Appears pink Appears pink onycholysis onycholysis  Growth

Slide 27 Appendages of the Skin Skin glands (Figure 6-20) Skin glands (Figure 6-20)  Two types of sweat glands: Eccrine glands Eccrine glands Apocrine glands Apocrine glands

Slide 28 Appendages of the Skin Skin glands (cont.) Skin glands (cont.)  Sebaceous glands Secrete sebum Secrete sebum antifungal activity antifungal activity Found in dermis except in palms and soles Found in dermis except in palms and soles Secretion increases in adolescence; may lead to formation of pimples and blackheads Secretion increases in adolescence; may lead to formation of pimples and blackheads

Slide 29 Appendages of the Skin Skin glands (cont.) Skin glands (cont.)  Ceruminous glands Modified apocrine sweat glands Modified apocrine sweat glands cerumen (wax) cerumen (wax) Function of cerumen Function of cerumen  protect area from dehydration; excess secretion can cause blockage of ear canal and loss of hearing

Burns

Slide 31 Cycle of Life: Skin Children Children  Skin is smooth, unwrinkled, and characterized by elasticity and flexibility  Few sweat glands  Rapid healing

Slide 32 Cycle of Life: Skin Adults Adults  Development and activation of sebaceous and sweat glands  Increased sweat production Body odor Body odor  Increased sebum production Acne Acne

Slide 33 Cycle of Life: Skin Old age Old age  Decreased sebaceous and sweat gland activity Wrinkling (Figure 6-21) Wrinkling (Figure 6-21) Decrease of body’s ability to cool itself Decrease of body’s ability to cool itself