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The Integumentary System
Chapter 6 The Integumentary System
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6.1 Clinical Application Skin Cancer
Arises from non-pigmented epithelial cells in the deep layer of the dermis (cutaneous carcinomas) or from melanocytes (cutaneous melanomas) Cutaneous carcinoma are the most common. Develop from hard, dry, scaly growths that have reddish bases. Most common on neck, face, or scalp. They grow slowly and are usually cured with surgical removal or radiation treatment Cutaneous melanomas are pigmented with melanin. Most common on the back or limb, arising from normal appearing skin or a mole. 1 in 5 people in the US will develop skin cancer at some point
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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
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© 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
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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
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b: © The McGraw-Hill Companies, Inc./Al Telser, photographer
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) (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 Keratinized Thickest on palms and soles ( mm) 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
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Layers of the Epidermis
Stratum Basale – Stratum Spinosum – Stratum Granulosum – Stratum Corneum –
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Keratinocytes Majority of cells in epidermis
produce keratin, the fibrous protein that helps give skin it protective properties Tightly connected to one another by desmosomes Arise from the deepest part of the epidermis (stratum basale) Undergo almost continuous mitosis
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Melanocytes Spider-shaped epithelial cells that synthesize melanin (pigment that provides skin color) Found in the deepest layer of the epidermis Melanin is transferred to keratinocytes where it forms a pigment that protects the nucleus from UV radiation
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a: © M. Schliwa/Visuals Unlimited
Epidermis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Melanocytes located in the ________________ produce the dark pigment ___________ Melanin gives skin color and also absorbs _________ 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)
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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
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Merkel Cells Present in the ____________ junction
Intimately associated with disc-like sensory nerve endings. The combination is referred to as a Merkel disc Functions as a __________________
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Langerhans’ Cells Arise from _________________
They are active cells ____________ (macrophages)
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Dermis On average __________ 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
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Dermis There are actually two (2) layers to the dermis: ______________
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ______________ Areolar Thin Superficial Dermal papillae here Papillary layer _____________ Dense irregular C. T. Most of dermis Reticular layer (a)
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Papillary Layer of Dermis
Thin, superficial layer in which collagen and elastin fibers form a mat that is heavily infused with blood vessels Superficial surface forms dermal papillae that indent the overlying epidermis and contain pain & touch receptors; also responsible for __________
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Reticular Layer of the Dermis
Accounts for approx. ________ of the thickness of the dermis Houses dense, irregular connective tissue Collagen fibers give the dermis strength and resiliency that prevent most jabs and scrapes from penetrating it
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6.3: 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
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
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Nails Scale-like modification of the epidermis that provides protection Contain hard keratin Each nail has a ____________________ Lunula – _________________________
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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 papilla contains nourishing blood vessels Hair color is due to type and amount of __________ 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)
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Hair Present all over body except palms, soles, lips, nipples, and parts of external genitalia Main function of body hair: sense insects on skin before they sting us Scalp hair guards against physical trauma, heat loss, and sunlight Eyelashes shield eyes Nose hairs filter particles from the air
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Hair Follicles Extends from the surface to the dermis and contains the hair root A knot of sensory nerve endings, root hair plexus, wraps around each hair bulb Arrector pili muscles are smooth muscles that are attached to the follicle. They are responsible for “goose bumps” Hair color specifically due to eumelanin (dark hair), pheomelanin (white-blonde, red hair)
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Sebaceous (OIL) Glands
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Usually associated with hair follicles Holocrine glands Hair follicle (oblique section) Secrete sebum (fatty material and cellular debris) Sebaceous gland Absent on palms and soles Size is small on the body and trunk but large on the face, neck and upper chest © The McGraw-Hill Companies, Inc./Al Telser, photographer
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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 __________ Dermal papilla Eccrine glands Sebaceous gland Apocrine glands (scent) Duct Ceruminous glands found in _________ Hair follicle Eccrine sweat gland Mammary glands secrete _________ Apocrine sweat gland
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Merocrine (Eccrine) sweat glands
Simple coiled, tubular gland responsible mostly for maintaining body temperature More numerous and are particularly abundant on the __________________________ Secretory part located in dermis that has a duct that connects to epidermal pore Their secretion (sweat) is 99% H2O with some salts, traces of metabolic wastes, and lactic acid
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Apocrine sweat gland Largely confined to axillary and ano-genital areas; do not play a role in thermoregulation Larger than eccrine glands and their ducts empty into _____________ Secretion is same as eccrine with addition of fatty substances and proteins; odorless but when decomposed by bacteria on body it causes body odor Become active during __________
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6.4: Regulation of Body Temperature
Regulation of body temperature is vitally important because even slight shifts can disrupt rates of metabolic reactions. Normally body temp is close to 37ºC (98.6ºF) Skin plays a key role in the homeostatic mechanism that regulates body temperature.
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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
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Regulation of Body Temperature
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Control center Hypothalamus detects the deviation from the set point and signals effector organs. Receptors Thermoreceptors send signals to the control center. Effectors Dermal blood vessels dilate and sweat glands secrete. Stimulus Body temperature rises above normal. Response Body heat is lost to surroundings, temperature drops toward normal. too high Normal body temperature 37°C (98.6°F) too low Stimulus Body temperature drops below normal. Response Body heat is conserved, temperature rises toward normal. Receptors Thermoreceptors send signals to the control center. Effectors Dermal blood vessels constrict and sweat glands remain inactive. Effectors Dermal blood vessels constrict and sweat glands remain inactive. Control center Hypothalamus detects the deviation from the set point and signals effector organs. If body temperature continues to drop, control center signals muscles to contract involuntarily.
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Problems in Temperature Regulation
Hyperthermia – abnormally high body temperature Hypothermia – abnormally low body temperature
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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
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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.
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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)
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Burns First degree burn – superficial, partial-thickness
Destroys ____________ Second degree burn – deep, partial-thickness Exposure to __________ Destroys ________ Third degree burn – full-thickness Destroys _________ Results from ________ Autograft Allograft
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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%
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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
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