6.1: Introduction Two or more kinds of tissues grouped together and performing specialized functions constitutes an organ. The skin and its various structures make up the integumentary system. Composed of several tissue types Maintains homeostasis Protective covering Retards water loss Regulates body temperature Houses sensory receptors Contains immune system cells Synthesizes chemicals Excretes small amounts of wastes

© The McGraw-Hill Companies, Inc./Al Telser, photographer 6.2: Skin and Its Tissues Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epidermis Outer layer Stratified squamous epithelium Dermis Inner layer Contains collagenous and elastic fibers Subcutaneous layer (hypodermis) Beneath dermis Areolar and adipose C. T. Stratified squamous epithelium Dense irregular connective tissue Adipose tissue © The McGraw-Hill Companies, Inc./Al Telser, photographer

b: © The McGraw-Hill Companies, Inc./Al Telser, photographer Layers of Skin Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hair shaft Sweat gland pore Sweat Stratum corneum Stratum basale Epidermis Dermal papilla Basement membrane Capillary Tactile (Meissner’s) corpuscle Dermis Sweat gland duct Sebaceous gland Arrector pili muscle Sweat gland Lamellated (Pacinian) corpuscle Sub- cutaneous layer Hair follicle Adipose tissue Nerve cell process Blood vessels Muscle layer (a) (b) b: © The McGraw-Hill Companies, Inc./Al Telser, photographer

b: © The McGraw-Hill Companies, Inc./Al Telser, photographer Epidermis (a) Hair shaft Epidermis Hair follicle (b) Sebaceous gland Dermis Sweat Sweat gland pore Capillary Stratum corneum Stratum basale Dermal papilla Arrector pili muscle Lamellated (Pacinian) corpuscle Basement membrane Sweat gland Nerve cell process Adipose tissue Blood vessels Muscle layer Sweat gland duct Subcutaneous layer T Tactile (Meissner’s) corpuscle Lacks blood vessels Five layers: (top to bottom) Stratum corneum (dead, keratinized cells) Stratum lucidum (only in thick skin – palms, soles) Stratum granulosum Stratum spinosum Stratum basale (mitotic layer) Keratinized Thickest on palms and soles (0.8-1.4mm) Melanocytes provide melanin Rests on basement membrane Stratified squamous epithelium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale Basement membrane Dermal papilla Dermis (a) (b) b: © The McGraw-Hill Companies, Inc./Al Telser, photographer

a: © M. Schliwa/Visuals Unlimited Epidermis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Melanocytes located in the stratum basale produce the dark pigment melanin Melanin gives skin color and also absorbs UV light Pigment granule Nucleus Cell membrane (a) Cellular extension ofmelanocyte Epidermis Pigment granules Golgi apparatus Melanocyte nucleus Basement membrane Dermis a: © M. Schliwa/Visuals Unlimited (b)

Epidermis Heredity and environment determine skin color Genetic Factors Varying amounts of melanin Varying size of melanin granules Albinos lack melanin Physiological Factors Dilation of dermal blood vessels Constriction of dermal blood vessels Accumulation of carotene Jaundice Environmental Factors Sunlight UV light from sunlamps X-rays

Indoor Tanning and Skin Cancer 6.1 Clinical Application Indoor Tanning and Skin Cancer

Dermis On average 1.0-2.0mm thick Contains dermal papillae Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Contains dermal papillae Hair shaft Binds epidermis to underlying tissues Sweat gland pore Sweat Stratum corneum Epidermis Stratum basale Dermal papilla Dense irregular connective tissue Basement membrane Capillary Tactile (Meissner’s) corpuscle Muscle cells Dermis Sweat gland duct Sebaceous gland Arrector pili muscle Nerve cell processes Specialized sensory receptors Sweat gland Lamellated (Pacinian) corpuscle Sub- cutaneous layer Hair follicle Adipose tissue Nerve cell process Blood vessels Blood vessels Muscle layer (a) Hair follicles Glands

Dermis There are actually two (2) layers to the dermis: Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Papillary layer Areolar Thin Superficial Dermal papillae here Papillary layer Reticular layer Dense irregular C. T. Most of dermis Reticular layer (a)

6.3: Accessory Structures of the Skin Accessory structures of the skin originate from the epidermis and include: Nails Hair follicles Skin glands

Nails Protective coverings Three (3) parts: Nail plate Nail bed Lunula Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Protective coverings Lunula Nail bed Nail plate Three (3) parts: Nail plate Nail bed Lunula

Hair Follicles Epidermal cells Tube-like depression Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epidermal cells Tube-like depression Extends into dermis Three parts: Hair root Hair bulb Hair shaft (dead, epidermal cells) Hair papilla contains nourishing blood vessels Hair color is due to type and amount of melanin Arrector pili muscle Hair shaft Pore Sebaceous gland Hair root (keratinized cells) Arrector pili muscle Hair follicle Eccrine sweat gland H a i r b u l b Region of cell division Hair papilla Dermal blood vessels (a)

6.2 Clinical Application Hair Loss

© The McGraw-Hill Companies, Inc./Al Telser, photographer Sebaceous Glands Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Usually associated with hair follicles Hair follicle (oblique section) Holocrine glands Sebaceous gland Secrete sebum (fatty material and cellular debris) Absent on palms and soles © The McGraw-Hill Companies, Inc./Al Telser, photographer

Sweat Glands Also called sudoriferous glands Widespread in skin Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Also called sudoriferous glands Widespread in skin Hair shaft Pore Originates in deeper dermis or hypodermis Dermal papilla Sebaceous gland Eccrine glands Duct Hair follicle Apocrine glands (scent) Eccrine sweat gland Ceruminous glands Apocrine sweat gland Mammary glands

6.3 Clinical Application Acne

6.4: Regulation of Body Temperature Regulation of body temperature is vitally important because even slight shifts can disrupt rates of metabolic reactions. Skin plays a key role in the homeostatic mechanism that regulates body temperature.

Heat Production and Loss Heat is a product of cellular metabolism The most active body cells are the heat producers and include: Skeletal muscle Cardiac muscle Cells of certain glands such as the liver The primary means of heat loss is radiation Also there is conduction, convection and evaporation

Problems in Temperature Regulation Hyperthermia – abnormally high body temperature Hypothermia – abnormally low body temperature

Elevated Body Temperature 6.4 Clinical Application Elevated Body Temperature

6.5: Healing of Wounds and Burns Inflammation is a normal response to injury or stress. 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

Cuts A shallow cut results in epidermal cells along its margin to divide more rapidly than usual. A deep cut results in blood vessels breaking which causes a clot to form. Clot and dried tissue fluid form scab. Growth factors stimulate new tissue formation. Phagocytic cells remove dead cells and debris. Excess collagenous fibers may form scar.

Copyright © The McGraw-Hill Companies, Inc Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Site of injury Blood cells (a) (b) Scab Blood clot (c) (d) (e) Scab Scar tissue Scar tissue Fibroblasts (f) (g)

Burns First degree burn – superficial, partial-thickness Second degree burn – deep, partial-thickness Third degree burn – full-thickness Autograft Homograft Various skin substitutes

Rule of Nines for Adults Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Anterior head and neck 41/2% 41/2% Anterior and posterior head and neck 9% 41/2% Posterior head and neck 41/2% Anterior trunk 18% Anterior and posterior upper extremities 18% Posterior trunk 18% Anterior upper extremities 9% Anterior and posterior trunk 36% Posterior upper extremities 9% 41/2% 41/2% 41/2% 41/2% Perineum 1% 9% 9% 9% 9% Anterior lower extremities 18% Anterior and posterior lower extremities 36% Posterior lower extremities 18% 100%

6.6: Lifespan Changes Skin becomes scaly Age spots appear Epidermis thins Dermis becomes reduced Loss of fat Wrinkling Sagging Sebaceous glands secrete less oil Melanin production slows Hair thins Number of hair follicles decreases Nail growth becomes impaired Sensory receptors decline Body temperature unable to be controlled Diminished ability to activate Vitamin D