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Integumentary System Chapter 6
Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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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
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Skin and Its Tissues Epidermis Dermis Hypodermis (Subcutaneous layer)
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
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Layers of Skin 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)
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Layers of Skin
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Epidermis Lacks blood vessels, uses diffusion Keratinized (hardening)
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 (hardening) Thickest on palms and soles ( mm) (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 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)
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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 (b)
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Heredity and environment determine skin color
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 Cyanosis Environmental Factors Sunlight UV light from sunlamps X-rays
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Dermis On average 1.0-2.0mm thick
Contains dermal papillae, makes boundary uneven Binds epidermis to underlying tissues Hair shaft Dense irregular connective tissue Sweat gland pore Sweat Stratum corneum Nerve cell processes Specialized sensory receptors Meissner corpuscle: sensitive to light touch (fingers and lips) Pacinian corpuscle: responds to deep pressure and slow vibrations Epidermis Stratum basale 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 Blood vessels Muscle layer (a) Hair follicles Glands
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Dermis There are actually two (2) layers to the dermis:
Papillary layer Areolar Thin Superficial Dermal papillae here Papillary layer Reticular layer Dense irregular C. T. Most of dermis Reticular layer (a)
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Accessory Structures of the Skin
Accessory structures of the skin originate from the epidermis and include: Nails Hair follicles Skin glands
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Nails Protective coverings Three (3) parts: Nail plate Nail bed Lunula
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Hair Follicles 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 Eumelanin: dark hair Pheomelanin: white blonde and red hair Albinism: lacks melanin Arrector pili muscle Smooth muscle cells, attached to hair follicle Responsible for goose bumps 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)
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Sebaceous Glands Usually associated with hair follicles
Holocrine glands Secrete sebum (fatty material and cellular debris) Helps keep the hair and skin soft, pliable, and waterproof Hair follicle (oblique section) Sebaceous gland Absent on palms and soles
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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 Pore 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 Dermal papilla Sebaceous gland Duct Hair follicle Eccrine sweat gland Ceruminous glands External ear canal, wax Apocrine sweat gland Mammary glands
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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
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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
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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
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Burns First degree burn Second degree burn Third 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, dermis, and accessory structures Full-thickness Dry and leathery, varies from red to black to white May require transplant: autograft, homograft, or various skin substitutes
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Rule of Nines for Adults for Burns
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%
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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
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