Chapter 6 The Integumentary System and Body...
Transcript of Chapter 6 The Integumentary System and Body...
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Chapter 6 The Integumentary System and Body
Membranes
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Objectives
• Classify, compare the structure of, and give examples of each type of body membrane
• Describe the structure and function of the epidermis and dermis
• List and briefly describe each accessory organ of the skin
• List and discuss the three primary functions of the integumentary system
• List and describe major skin disorders and infections • Classify burns and describe how to estimate the extent
of a burn injury
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Classification of Body Membranes
• Classification of body membranes – Epithelial membranes—composed of
epithelial tissue and an underlying layer of connective tissue
– Connective tissue membranes—composed exclusively of various types of connective tissue
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Classification of Body Membranes
• Epithelial membranes – Cutaneous membrane—the skin – Serous membranes—simple squamous
epithelium on a connective tissue basement membrane
• Parietal—line walls of body cavities • Visceral—cover organs found in body cavities
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Classification of Body Membranes
• Examples – Pleura—parietal and visceral layers line
walls of thoracic cavity and cover the lungs – Peritoneum—parietal and visceral layers
line walls of abdominal cavity and cover the organs in that cavity
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Classification of Body Membranes
• Diseases – Pleurisy—inflammation of the serous
membranes that line the chest cavity and cover the lungs
– Peritonitis—inflammation of the serous membranes in the abdominal cavity that line the walls and cover the abdominal organs
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Classification of Body Membranes
• Mucous membranes – Line body surfaces that open directly to the
exterior – Produce mucus, a thick secretion that
keeps the membranes soft and moist
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Classification of Body Membranes
• Connective tissue membranes – Do not contain epithelial components – Produce a lubricant called synovial fluid – Examples
• The synovial membranes in the spaces between joints and in the lining of the bursal sacs
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The Skin
• Structure—two primary layers called epidermis and dermis – Epidermis
• Outermost and thinnest primary layer of skin • Composed of several layers of stratified
squamous epithelium
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The Skin
• Structure – Epidermis
• Stratum germinativum—innermost (deepest) layer of cells that continually reproduce; new cells move toward the surface
– Sometimes called the pigment layer – Pigment cells called melanocytes, which produce the brown
pigment melanin • As cells approach the surface, they are filled with a tough,
waterproof protein called keratin and eventually flake off • Stratum corneum—outermost layer of keratin-filled cells
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The Skin
• Structure – Epidermis
• Skin color changes – Pink flush indicates increased blood volume or increased
blood oxygen – Cyanosis—bluish gray color indicates decreased blood
oxygen level – Vitiligo—patchy light skin areas resulting from acquired
loss of epidermal melanocytes (Figure 6-4) – Increased skin pigmentation caused by hormonal changes
in pregnant women – Freckles—small, flat macules—common normal skin
pigment variation
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The Skin
• Dermal-epidermal junction—specialized area of contact between the epidermis and dermis; sometimes described as “spot welds” – Provide support for epidermis – Weakened or destroyed junctions can
cause blisters
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The Skin
• Structure – Dermis
• Deeper and thicker of the two primary skin layers and composed largely of connective tissue
• Upper area of dermis characterized by parallel rows of peglike dermal papillae
• Thick skin has parallel friction ridges and no hairs • Thin skin has irregular, shallow grooves and hair • Deeper area of dermis is filled with network of tough
collagenous and stretchable elastic fibers
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The Skin
• Structure – Dermis
• Number of elastic fibers decreases with age and contributes to wrinkle formation
– Striae—“stretch marks”; elongated marks caused by overstretching of skin
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The Skin
• Structure – Dermis
• Dermis also contains nerve endings, muscle fibers, hair follicles, sweat and sebaceous glands, and many blood vessels
– Birthmarks—malformation of dermal blood vessels » Strawberry hemangioma » Port-wine stain » Stork bite
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The Skin
• Appendages of the skin – Hair
• Soft hair of fetus and newborn called lanugo • Hair growth requires epidermal tubelike
structure called hair follicle • Hair growth begins from hair papilla
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The Skin
• Appendages of the skin – Hair
• Hair root lies hidden in follicle; visible part of hair called shaft
• Alopecia (Figure 6-8)—hair loss • Arrector pili—specialized smooth muscle that
produces “goose pimples” and causes hair to stand up straight
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The Skin
• Appendages of the skin – Receptors
• Specialized nerve endings—make it possible for skin to act as a sense organ
– Meissner (tactile) corpuscle—capable of detecting light touch
– Lamellar (Pacini) corpuscle—capable of detecting pressure
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The Skin
• Nails – Produced by epidermal cells over terminal ends of
fingers and toes – Visible part called nail body – Root lies in a groove and is hidden by cuticle – Crescent-shaped area nearest root called lunula – Nail bed may change color with change in blood
flow
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The Skin
• Nails – Normal variations in nail structure
• Longitudinal ridges in light-skinned individuals • Pigmented bands in dark-skinned individuals
– Abnormal variations in nail structure • Onycholysis—separation of nail from nail bed • Pitting—common in psoriasis
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The Skin
• Skin glands—two main types – Sweat, or sudoriferous – Sebaceous
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The Skin
• Skin glands – Sweat, or sudoriferous, glands
• Eccrine sweat gland – Most numerous, important, and widespread of the
sweat glands – Produce perspiration or sweat, which flows out
through pores on skin surface – Function throughout life and assist in body heat
regulation
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The Skin
• Skin glands – Sweat or sudoriferous glands
• Apocrine sweat glands – Found primarily in axilla and around genitalia – Secrete a thicker, milky secretion quite different from
eccrine perspiration – Breakdown of secretion by skin bacteria produces
odor
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The Skin
• Skin glands – Sebaceous glands
– Secrete oil or sebum for hair and skin – Secretion increases during adolescence – Amount of secretion regulated by sex hormones – Sebum in sebaceous gland ducts may darken to
form a blackhead – Acne vulgaris—inflammation of sebaceous gland
ducts
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Functions of the Skin
• Protection—first line of defense – Against infection by microbes – Against ultraviolet rays from sun – Against harmful chemicals – Against cuts and tears – Bruising can cause discoloration as blood
released from damaged vessels breaks down – Skin grafts may be needed to replace skin
destroyed by disease or trauma
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Functions of the Skin
• Temperature regulation – Skin can release almost 3000 calories of
body heat per day – Mechanisms of temperature regulation
• Regulation of sweat secretion • Regulation of flow of blood close to the body
surface
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Functions of the Skin
• Sense organ activity – Receptors serve as receivers for the body,
keeping it informed of changes in its environment
– Skin can detect sensations of light touch, pressure, pain, heat, and color
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Disorders of the Skin (Dermatoses)
• Skin lesions—any measurable variation from the normal structure – Elevated lesions—cast a shadow outside their
edges • Papule—small, firm raised lesion • Plaque—large raised lesion • Vesicle—blister • Pustule—pus-filled lesion • Crust—scab • Wheal (hive)—raised, firm lesion with a light center
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Disorders of the Skin (Dermatoses)
– Flat lesions—do not cast a shadow • Macule—flat, discolored region
– Depressed lesions cast a shadow within their edges
• Excoriation—missing epidermis, as in a scratch • Ulcer—craterlike lesion • Fissure—deep crack or break
– Some lesions are produced by scrapes and cuts—the skin can repair itself
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Burns
• Treatment and recovery or survival depend on total area involved and severity or depth of the burn
• Classification of burns – First-degree (partial-thickness) burns—only
surface layers of epidermis involved – Second-degree (partial-thickness) burns—
involve deep epidermal layers; always cause injury to upper layers of the dermis
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Burns
• Classification of burns – Third-degree (full-thickness) burns—
characterized by complete destruction of the epidermis and dermis
• May involve underlying muscle and bone (fourth degree)
• Lesion is insensitive to pain because of destruction of nerve endings immediately after injury—intense pain is experienced soon thereafter
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Burns
• Estimating body surface area using the “rule of nines” in adults – Body divided into 11 areas of 9% each – Additional 1% of body surface area around
genitals
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Skin Infections
• Impetigo—highly contagious staphylococcal or streptococcal infection
• Tinea—fungal infection (mycosis) of the skin; several forms occur
• Warts—benign neoplasm caused by papillomavirus
• Boils—furuncles; staphylococcal infection in hair follicles
• Scabies—parasitic infection
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Vascular and Inflammatory Skin Disorders
• Decubitus ulcers (bedsores) develop when pressure slows down blood flow to local areas of the skin
• Urticaria or hives—red lesions caused by fluid loss from blood vessels
• Scleroderma—disorder of vessels and connective tissue characterized by hardening of the skin; two types: localized and systemic
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Vascular and Inflammatory Skin Disorders
• Psoriasis—chronic inflammatory condition accompanied by scaly plaques
• Eczema—common inflammatory condition characterized by papules, vesicles, and crusts; not a disease itself but a symptom of an underlying condition
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Skin Cancer
• Three common types – Squamous cell carcinoma—the most
common type, characterized by hard, raised tumors
– Basal cell carcinoma—characterized by papules with a central crater; rarely spreads
– Melanoma—malignancy in a nevus (mole); the most serious type
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Skin Cancer
• The most important causative factor in common skin cancers is exposure to sunlight
• Kaposi sarcoma, characterized by purple lesions, is associated with AIDS and other immune deficiencies
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