Chapter 6 Integumentary System Copyright The Mc GrawHill

Chapter 6 Integumentary System Copyright The Mc. Graw-Hill Companies, Inc. Permission required for reproduction or display. 1

Introduction • Two or more kinds of tissues grouped together and performing specialized functions constitutes an organ. • The skin (largest organ) and its various accessory structures (hair, nails, sensory receptors, and glands) make up the integumentary system. • Composed of several tissue types and contains immune system cells • Functions – – – – Maintains homeostasis Protective covering Retards water loss Regulates body temperature Houses sensory receptors Synthesizes chemicals Excretes small amounts of wastes Helps produce vitamin D 2

Skin and Its Tissues Epidermis • Outer layer • Stratified squamous epithelium Dermis • Thicker, inner layer • Connective tissue containing collagenous and elastic fibers, epithelial tissue, smooth muscle tissue, nervous tissue, and blood • Basement membrane anchors the epidermis to the dermis and separates the two layers Hypodermis (Subcutaneous layer) • Beneath dermis • Areolar and adipose C. T. • Not a true layer Stratified squamous epithelium Dense irregular connective tissue Adipose tissue 3

Layers of Skin Hair shaft Sweat gland pore Sweat Epidermis Stratum corneum Stratum basale Dermal papilla Basement membrane Dermis Capillary Tactile (Meissner’s) corpuscle Sweat gland duct Sebaceous gland Arrector pili muscle Sweat gland Subcutaneous layer Lamellated (Pacinian) corpuscle Hair follicle Adipose tissue Nerve cell process Blood vessels Muscle layer (a) (b) 4

Layers of Skin 5

Epidermis 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) • • Lacks blood vessels, uses diffusion Keratinized (hardening) Thickest on palms and soles (0. 8 -1. 4 mm) Melanocytes provide melanin Rests on basement membrane Stratified squamous epithelium Shields underlying tissues from water loss, injury, and harmful chemicals • When intact keeps out pathogens Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale Basement membrane Dermal papilla Dermis (a) (b) 6

Epidermis • 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 7 (b)

Epidermis Heredity and environment determine skin color Genetic Factors • Varying amounts of melanin • Varying size of melanin granules • Albinos lack melanin Environmental Factors • Sunlight • UV light from sunlamps • X-rays Physiological Factors • Dilation of dermal blood vessels • Constriction of dermal blood vessels • Accumulation of carotene • Jaundice • Cyanosis 8

Dermis • On average 1. 0 -2. 0 mm thick • Contains dermal papillae, makes boundary uneven • Binds epidermis to underlying tissues • Dense irregular connective tissue • Nerve cell processes • Specialized sensory receptors Epidermis Dermis – Meissner corpuscle: sensitive to light touch (fingers and lips) – Pacinian corpuscle: responds to deep pressure and slow vibrations • Blood vessels • Hair follicles • Glands Subcutaneous layer Hair shaft Sweat gland pore Sweat Stratum corneum Stratum basale Dermal papilla Basement membrane Capillary Tactile (Meissner’s) corpuscle Sweat gland duct Sebaceous gland Arrector pili muscle Sweat gland Lamellated (Pacinian) corpuscle Hair follicle Adipose tissue Nerve cell process Blood vessels Muscle layer (a) 9

Dermis • There actually two (2) layers to the dermis: • Papillary layer • Areolar • Thin • Superficial • Dermal papillae here • Reticular layer • Dense irregular C. T. • Most of dermis Papillary layer Reticular layer (a) 10

Accessory Structures of the Skin • Accessory structures of the skin originate from the epidermis and include: – Nails – Hair follicles – Skin glands 11

Nails • Protective coverings • Three (3) parts: • Nail plate • Nail bed • Lunula Nail bed Nail plate 12

Hair Follicles • • Epidermal cells Tube-like depression Extends into dermis Three parts: • • • Hair shaft Hair root Hair bulb Hair shaft (dead, epidermal cells) Pore • Hair papilla contains nourishing blood vessels • Hair color is due to type and amount of melanin Sebaceous gland Hair root (keratinized cells) Arrector pili muscle – Eumelanin: dark hair – Pheomelanin: white blonde and red hair – Albinism: lacks melanin Hair follicle Eccrine sweat gland Hair bulb Region of cell division • Arrector pili muscle Hair papilla – Smooth muscle cells, attached to hair follicle – Responsible for goose bumps Dermal blood vessels (a) 13

Sebaceous Glands • Usually associated with hair follicles • Holocrine glands • Secrete sebum (fatty material and cellular debris) Hair follicle (oblique section) Sebaceous gland – Helps keep the hair and skin soft, pliable, and waterproof • Absent on palms and soles 14

Sweat Glands • • Also called sudoriferous glands Exocrine gland, widespread in skin Originates in deeper dermis or hypodermis Eccrine glands – Most abundant – Forehead, neck and back – Carried up to the surface through a pore Hair shaft • Apocrine glands – Become active at puberty – Numerous in axillary regions and groin – Ducts open into hair follicles – Develop a scent when metabolized by skin bacteria • Ceruminous glands – External ear canal, wax • Mammary glands Pore Dermal papilla Sebaceous gland Duct Hair follicle Eccrine sweat gland Apocrine sweat gland 15

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 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 • Hyperthermia – abnormally high body temperature • Hypothermia – abnormally low body temperature 16

Healing 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 17

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. • In large, open wounds, healing may be accompanied by formation of small, rounded masses called granulations 18

Burns • First degree burn – Injuring the epidermis alone – Superficial, partial-thickness – Heals in 1 -2 weeks with no scarring • Second degree burn – Destroys some epidermis as well as some dermis – Deep, partial-thickness – Blisters appear, becomes moist and firm, varies from dark red to waxy white – Healing depends upon accessory structures of the skin that survive the injury • Third degree burn –Destroys the epidermis, and accessory structures –Full-thickness –Dry and leathery, varies from red to black to white –May require transplant: autograft, homograft, or various skin substitutes 19

Rule of Nines for Adults for Burns 41/2% Anterior and posterior head and neck 9% 41/2% Anterior head and neck 4 1/2% Anterior trunk 18% Anterior and posterior upper extremities 18% Anterior upper extremities 9% 41/2% Anterior and posterior trunk 36% Posterior head and neck 4 1/2% Posterior trunk 18% Posterior upper extremities 9% 41/2% Perineum 1% 9% Anterior lower extremities 18% 9% 9% Anterior and posterior lower extremities 36% 9% Posterior lower extremities 18% 20 100%

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 21