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Integumentary System Skin (integument) is the principal organ. Appendages – hair, nails, and skin glands Body Membranes Epithelial – epithelial tissue and an underlying layer of specialized connective tissue Connective – exclusively various types of connective tissue Epithelial Membranes 1. Cutaneous – skin 2. Serous – only on surfaces of closed cavities A. Parietal – lines wall of a body cavity B. Visceral – covers the surface of organs in the body cavity 3. Mucous – line body surfaces opening directly to exterior, produce mucus (soft, moist) Serous Membranes Thoracic Cavity – pleura Abdominal Cavity – peritoneum Pleurisy – inflammation of the serous membranes that line the chest cavity and lungs Peritonitis – inflammation of the serous membranes in the abdominal cavity that line the walls and cover the abdominal organs Connective Tissue Membranes Do not contain epithelial components Synovial membranes – lines spaces between bones and joints; secret a thick and colorless lubricating fluid called synovial fluid Line small, cushion like sacs called bursae found between moving body parts Activity Differentiate a cutaneous membrane from a serous membrane. There are two types of serous membranes, parietal and visceral. What is the difference? Name the serous membranes in the thoracic cavity. Name the serous membranes in the abdominal cavity. Answers Cutaneous-skin, Serous-on surfaces only in enclosed cavities Parietal lines the walls of a body cavity, visceral covers the surface of organs in the body cavity Parietal and visceral pleura Parietal and visceral peritoneum Structure of the Skin Epidermis – outermost layer, stratified squamous epithelium Dermis – deeper layer, largely connective tissue Hypodermis-subcutaneous tissue, loose layer of connective tissue and fat, insulation, stored energy and food source, protection, shock-absorbing pad Epidermis Stratum germinativum – innermost layer, undergo mitosis and reproduce themselves As new cells approach the surface, the cytoplasm is replaced with keratin Keratin – tough, waterproof material that provides cells of the outer layer with an abrasion-resistant, protective quality Stratum corneum – tough outer layer, where dry, dead cells “flake off” The deepest cell layer of the epidermis produces a special pigment that gives color to the skin. Melanin – brown pigment produced by specialized cells called melanocytes Cyanosis – skin turns bluish-gray color Blisters – caused by breakdown of union between cells or primary layers of the skin Activity Differentiate the dermis and epidermis. What is keratin? What is the stratum corneum? What are melanocytes? What causes blisters? Dermis Cells scattered apart with many fibers in between Collagen or white fibers – tough and strong Elastic or yellow fibers – stretchable, elastic Dermal papillae – parallel rows of peg-like projections, helps bind skin layers together and forms ridges and grooves for fingerprints (develop before birth) Deeper areas of dermis are filled with a dense network of tough collagenous and stretchable elastic fibers Number of elastic fibers decreases with age (wrinkles) Dermis also contains nerve endings, muscle fibers, hair follicles, sweat and sebaceous glands, and many blood vessels Appendages of the Skin Lanugo – soft hair of fetus and newborn Hair growth begins when cells of the epidermal layer of the skin grow down into the dermis, forming a hair follicle Hair growth begins from a small, cupshaped cluster of cells called the hair papilla The hair papilla (nourished by blood vessel) is located in the hair bulb at the base of the follicle Root – part of hair that lies hidden in the follicle Shaft – visible part of hair, extends from follicle New hair will grow as long as cells in the papilla of the hair follicle remain alive Alopecia – hair loss of any kind Arrector pili – involuntary smooth muscle that causes hair to stand up (goose pimples) Receptors Free nerve endings – respond to pain and changes in temperature Meissner’s (tactile) corpuscle – capable of detecting light touch Pacinian corpuscle – capable of detecting pressure Krause’s end bulbs – detect sensations of touch and low frequency vibrations Nails Produced by epithelial cells over terminal ends of fingers and toes Nail body – visible part of nail Cuticle – fold of skin Root – hidden by cuticle Lunula – crescent-shaped area nearest root Nail bed – contains blood vessels, changes color with change in blood flow Skin Glands Two types 1. Sweat or sudoriferous A. Eccrine– most numerous, perspiration through pores on skin surface, body heat regulation B. Apocrine – axilla and genitalia, thick and milky secretion, breakdown of secretion by bacteria causes odor 2. Sebaceous – oil, grows where hair grows Secretes oil or sebum for hair and skin More secretion during adolescence Regulated by sex hormones Sebum in ducts may darken to form blackhead Acne vulgaris – inflammation of sebaceous gland ducts Think! Draw a square inch box to represent a square inch of skin tissue. List some of the structures that fit into one square inch of skin. Answers 500 Sweat glands Over 1,000 nerve endings Yards of tiny blood vessels 100 oil or sebaceous glands 150 sensors for heat (hot and cold) Millions of cells Dermatoses: Disorders of the Skin 1. Elevated skin lesions a. Papule – small, firm b. Plaque – large, raised c. Vesicle – blister d. Pustule – pus-filled e. Crust – scab f. Wheal - hive 2. Flat skin lesions a. Macule – flat, discolored 3. Depressed lesions a. Excoriation - scratch b. Ulcer – crater like c. Fissure – deep crack or break Burns Rule of Nines – See page 167 First-degree: only surface layers of epidermis involved, no blistering Second-degree: involve deep epidermal layers and always cause injury to upper layers of dermis; blistering, swelling, severe pain, fluid loss Note: Deep second-degree burns damage sweat glands, hair follicles, and sebaceous glands. Third-degree or full-thickness burns (fourth degree): complete destruction of epidermis and dermis, nerve endings destroyed Third-degree burns often involve bone and muscle (full-thickness). The lesions are insensitive to pain immediately after injury because of the destruction of nerve endings. Intense pain is soon experienced; the fluid loss is serious problem. Skin Infections Impetigo – highly contagious staphylococcal infection Tinea – fungal infection Warts – benign neoplasms caused by papillomavirus Boils – furuncles; staphylococcal infection in hair follicles Vascular and Inflammatory Skin Disorders Decubitus ulcers – bedsores; pressure slows down blood flow Urticaria – hives; fluid loss from blood vessels Scleroderma – disorder of vessels and connective tissue; hardening of the skin Psoriasis – chronic inflammatory condition; scaly plaques Eczema – common inflammatory condition; papules, vesicles, and crusts; a symptom of an underlying condition Skin Cancer Squamous cell carcinoma – most common; hard, raised tumors 2. Basal cell carcinoma – papules with a central crater; rarely spreads 3. Melanoma – most serious; malignancy in a nevus (mole) Kaposi sarcoma – purple lesions; AIDS and other immune deficiencies Exposure to sunlight – causative factor 1.