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Skin and Integumentary System “A covering for everything and everything under its cover” I. Classification of Body Membranes A. membrane - a thin, sheet-like structure that has an important function Ex. cover and protect body surfaces line the body cavities cover the inner surfaces of hollow organs secrete lubricating fluids to reduce friction B. There are two main types of body membranes: 1. epithelial membranes - made up of epithelial tissue and an underlying layer of connective tissue 2. connective tissue membranes - composed entirely of different types of connective tissue C. There are three types of epithelial tissue membranes: cutaneous membranes,serous membranes, mucous membranes 1. The cutaneous membrane is the skin. It is one of the largest organs; composes 16% of the body weight. 2. Serous membranes line body cavities and cover the surface of internal organs. a. It is one continuous membrane that lines each of the body cavities. 1. There is a pleural membrane that lines the thoracic cavity and covers the organs in the t thorax. 2. There is a peritoneal membrane that lines the abdominal cavity and covers the organs in the abdomen. b. The part of a serous membrane that lines the body cavity is known as the parietal portion. c. The portion of the membrane that covers the internal organs is known as the visceral portion. d. The suffix “itis” means inflammation. What do you think the terms “peritonitis” and “pleuritis” mean? 3. Mucous membranes are epithelial membranes that line body surfaces that open to the outside. a. Ex. membranes lining the respiratory, the digestive, the urinary, and the reproductive tracts. b. The epithelial cells secrete a thick , slimy material known as mucus that keeps the membrane moist and soft. D. Connective tissue membranes lack epithelial tissue. 1. One type lines the body’s joints. a. They are called synovial membranes. b. They are smooth and slick and secrete a thick lubricating fluid called synovial fluid. c. Synovial membranes line the small cushionlike sacs that are found between many of the body’s moving parts; these sacs are called bursae. (What would the term bursitis mean?) II. Skin A. The skin is called a cutaneous membrane. 1. The skin consists of two layers: the epidermis and the dermis. 2. The epidermis is the outermost layer and consists of stratified squamous epithelium. a. The epidermis is made of many layers of cells 1) stratum basale or germinativum the innermost layer undergoes mitosis produces new skin cells that allows the skin to repair itself . gives color to the skin contains melanocytes that produce melanin 2) Stratum spinosum – daughter cells 3) Stratum granulosum – Cells becoming flatter as they rise to the surface, filling with keratin begins 4)Stratum lucidium – only on hairless and thick parts of the body palms and soles of feet 5) stratum corneum - the outer layer of skin with cells filled with keratin – (a tough, water proof material these cells are dead and are shed from the skin) 3. The dermis is the deeper layer and is composed mainly of connective tissue. a. contains many collagen fibers that strengthen the skin and allow it to be flexible and elastic b. upper layers contain peg-like projections called dermal papillae that form the ridges and grooves that form our finger prints c. contains nerves and nerve endings that provide sensory information d. contains muscle fibers, sweat and oil glands, blood vessels and hair follicles 4. The skin is supported by a thick layer of fat and connective tissue called the subcutaneous tissue. B. Skin Appendages 1. hair covers the human body a. grows from hair follicles in the dermis b. hair shaft is the visible part of the hair; the hair root is the hidden part of the hair c. arrector pili muscle - cause the hair to “stand on end” and cause “goose pimples” d. lanugo - the fine and soft hair that covers much of the body in newborn infants 2. receptors provide sensory information - touch, pain, temperature, and pressure a. pacinian corpuscle - detects pressure on the skin b. Meissner’s corpuscle - detects light touch c. free nerve endings detect pain d. Krause’s end bulbs detect cold e. other receptors detect heat, crude touch, and vibrations 3. nails are composed of keratin and become hard and platelike a. cover the ends of the toes and fingers b. nail body is the visible part of the nail c. nail root lies hidden in the nail cuticle d. lunula - white crescent shaped area closest to the cuticle e. nail bed - layer of epithelium under the nail 4. skin glands a. two types of glands – sudoriferous -sweat glands sebaceous glands b. sweat glands - two types i. eccrine glands most numerous produce prespiration pores - openings through sweat is released1 square inch of skin has 3000 sweat glands ii. apocrine glandsin the armpit and genital area produce a thick, milky secretion skin bacteria breakdown the secretion and produce a strong odor c. sebaceous glands – i. grow where hair grows ii. their secretion is called sebum - lubricates the hair and skin prevents drying and cracking of the skin iii. increases during adolescence - causes pimples sebum can darken and form blackheads C. Functions of the skin 1. Protection - “Our first line of defense” a. The tough keratin filled cells protect against the entry of harmful bacteria and chemicals b. The tough cells resist tears and cuts. c. The skin is water tight and protects a against water loss d. The melanin protects against UV rays. 2. Temperature regulation a. The skin regulates temperature by regulating the flow of sweat and the flow of blood near the surface. b. Evaporation of sweat cools the body. Vasodilation - Increased blood flow causes heat loss by radiation. Vasoconstriction – conserves heat by restricting the flow of blood 3. Sense Organ Activity (nerves) – interacting with the environment to help us respond appropriately D. Burns 1. Burns can be caused by fire, contact with a hot surface, over exposure to UV radiation, electricity, or a chemical 2. Recovery from burns depends on the severity of the burn and the total area of skin involved. 3. Rule of nines - rule to estimate the extent of a burn a. The body is divided into 11 areas that are about 9% of the surface area. b. See the chart on page 125 4. Classification of burns a. first degree burns - involves the superficial layers minor discomfort and reddening no blistering superficial layers may peal b. second degree burns - involves the deep epidermal layers damages the sweat glands and hair follicles blisters occur causes severe pain, swelling and fluid loss scarring is common c. third degree burns - complete destruction of epidermis and dermis tissue death often extends into the subcutaneous area damage often involves the underlying muscle and bone usually little or no pain immediately after the injury due to nerve injury fluid loss is severe III. Skin Cancer A. Most skin tumors are benign, but there are some that are cancerous. B. The most important risk factor for the development of skin cancer is exposure to sunlight (UV rays). Frequent exposure to chemicals, irritation, and infection also seem to be risk factors. C. There are three types of skin cancer: basal cell carinoma, squamous cell carcinoma, and malignant melanoma. D. Basal Cell Carcinoma - the least cancerous of the skin cancers. The cancer is slow growing and slow to metastasize. They occur most often on sun exposed areas of the face or head. The lesions appear as nodules that become ulcerated. This cancer is usually curable. E. Squamous Cell Carcinoma - grows rapidly and spreads if not treated. Seems to be related to sun exposure. Found most often on the scalp, ears, nose, dorsum of the hands and lower lip. The growth starts as a scaley, reddened bump that forms a shallow ulcer. F. Malignant Melanoma - a cancer of the melanocytes. It is the most aggressive of the skin cancers. It grows rapidly and metastasizes early. It can occur anywhere there is pigment; sometimes develops from moles. It usually appears as a spreading brown to black patch on the skin. American Cancer Society suggests using the ABCD rule for recognizing malignant melanoma: A = asymmetry - the two sides of the spot or mole do not match. B = border irregularity - the borders of the spot or mole are not smooth, but have indentations. C = color - the spot or mole contains areas of different colors (blacks, browns, tans, and maybe reds and blues) D = diameter - the spot is larger than 6 mm in diameter (the size of a pencil eraser) Whenever you notice an odd mole or spot on your body it is always important to check for it. Here are some easy ways you can remember what to look for! By: Becky Walls A= Asymmetry If you draw a line through this mole, the two halves will not match. B= Border Irregularity When the Borders of the lesion are not smooth but exhibit indentations. The edges may be scalloped or notched. C= Color When the pigmented spot contains areas of different colors. (Blacks, browns, reds, tans, blues) D= Diameter If the spot is any larger than 6mm in diameter. E= Evolving Any change — in size, shape, color, elevation, or another trait, or any new symptom such as bleeding, itching or crusting — points to danger. Birthmarks Birthmarks range from hardly noticeable to disfiguring. The two main types of birthmarks 1. red, vascular birthmarks - happen when blood vessels don't form correctly — either there are too many of them or they're wider than usual. . 2. pigmented birthmarks - caused by an overgrowth of the cells that create pigment in skin. Nearly all are harmless, but it is important to talk to the doctor for the few occasions when it is not harmless. Vascular Birthmarks Macular Stains – appear darker as a child cries Hemangioma “Strawberries”, “Angel Kisses”, “Stork bites” Disappear at about 9yrs Port Wine Stains need treatment as they continue to grow throughout life Pigmented Birthmarks Café Au Lait marks look like coffee with milk, one is OK but more than one needs to be checked for and nerve disorder Mongolian spots – grey blue patches usually on the lower body. Disappear by school age Moles – also called Nevus, Can have various skin colors, be flat or raised. Can be present at birth or come later. Only very large or changing moles need to be checked for melanoma throughout life.