The Integumentary System Bethany, Susan

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The Integumentary System Bethany, Susan

  1. 1. The Integumentary System By: Susan Zavaski and Bethany Sharpless 10/17/08
  2. 2. Overview! <ul><li>What the integumentary system is </li></ul><ul><li>Structure and function of the system </li></ul><ul><li>The epidermis and the dermis </li></ul><ul><li>Pigmentation </li></ul><ul><li>Functions of the hair, nails, glands, and repair. </li></ul><ul><li>Clinical applications </li></ul><ul><li>Related careers </li></ul>
  3. 3. What is the Integumentary (Integument) System? <ul><li>The system of the body consisting of: </li></ul><ul><ul><li>The Skin </li></ul></ul><ul><ul><li>Hair </li></ul></ul><ul><ul><li>Nails </li></ul></ul><ul><ul><li>Glands </li></ul></ul>
  4. 4. Structure <ul><li>Consists of three major parts: </li></ul><ul><ul><li>Accessory structures </li></ul></ul><ul><ul><ul><li>Hair, nails, and glands. </li></ul></ul></ul><ul><ul><li>The cutaneous membrane (the skin, which is composed of the epidermis) </li></ul></ul><ul><ul><li>The connective tissues of the dermis. </li></ul></ul>
  5. 5. ~The 5 Functions~ <ul><li>Protection : Protects organs and tissue from harm. </li></ul><ul><li>Temperature maintenance: Keeps normal body temperature; adapts to environment. </li></ul><ul><li>Synthesis and storage of nutrients: Epidermis and dermis convert and store different nutrients. </li></ul><ul><li>Sensory reception: detects touch and temperature and gives the information to the brain. </li></ul><ul><li>Excretion and secretion: Excretes and secretes various products. </li></ul>
  6. 6. The Epidermis (Basics) <ul><li>Consists of 4 or 5 different layers </li></ul><ul><li>On the soles of feet and palms of hands there is 5 layers. </li></ul><ul><li>Anywhere else on the body only has 4 layers. </li></ul><ul><li>In order from deepest to closest to the surface: stratum germinativum, stratum spinosum, stratum granulosum, stratum lucidum, with 5 layers the final layer is the stratum corneum. </li></ul>
  7. 7. More Basics! <ul><li>Usually takes 2-4 weeks for a cell to make it from the first to the last layer. </li></ul><ul><li>In doing this, its oxygen supply becomes cut-off and keratin is packed in until the cell dies. </li></ul><ul><li>Takes about 2 weeks to be shed from the outermost layer of the skin. </li></ul><ul><li>As old layers are lost, new come in. </li></ul>
  8. 8. The Stratum Germinativum (Basale) <ul><li>The deepest layer of the epidermis. </li></ul><ul><li>Separates the connective tissue of the dermis from the epidermis </li></ul><ul><li>The layer that allows new cell growth and is full of germinative cells. </li></ul><ul><li>Also produced here are melanocytes, which colors the epidermis. </li></ul><ul><li>Forms epidermal ridges (provides contact between both layers)and dermal papillae (extend between the ridges). These increase surface area for diffusion between the epidermis and dermis, which is vital for nutrients in the epidermis. </li></ul>
  9. 9. The 3 Intermediate Layers <ul><li>The stratum spinosum </li></ul><ul><ul><li>Cells continue to divide and add thickness. </li></ul></ul><ul><li>The stratum granulosum </li></ul><ul><ul><li>Cells stop dividing and make keratin (coats the skin surface and forms basic structures for nails, hair, and calluses. </li></ul></ul><ul><li>The stratum lucidum </li></ul><ul><ul><li>Covers the stratum granulosum and cells are filled with keratin. </li></ul></ul>
  10. 10. The Stratum Corneum <ul><li>The outermost layer of the skin (found on the palms and soles). </li></ul><ul><li>15-30 layers of dead epithelial cells that become cornified. </li></ul><ul><li>Generally shed in larger groups due to the amount of keratinized cells. </li></ul>
  11. 11. The Dermis! <ul><li>Lies below the epidermis </li></ul><ul><li>Consists of a papillary layer and a reticular layer </li></ul>
  12. 12. Layers of the Dermis <ul><li>Papillary Layer </li></ul><ul><ul><li>Made up of loose connective tissue that both supports and nourishes the epidermis. </li></ul></ul><ul><ul><li>Also has capillaries and nerves that supply the surface of the skin. </li></ul></ul><ul><li>Reticular layer </li></ul><ul><ul><li>Made up of irregular connective tissue and bundles of collagen that blend into the papillary layer. It also provides support and flexibility for the dermis. </li></ul></ul>
  13. 13. The Subcutaneous Layer (hypodermis) <ul><li>Stabilizes the position of the skin to the tissues and organs beneath. </li></ul><ul><li>Loose connective tissue with a lot of fat cells that many consider “baby fat.” </li></ul><ul><li>Very elastic and has no vital organs and very few capillaries which makes the layer an ideal place for injections by means of a hypodermic needle. </li></ul>
  14. 14. Pigmentation <ul><li>Caused by carotene and melanin . </li></ul><ul><li>Carotene is an orange-yellow color and is responsible for some vitamin A production. </li></ul><ul><li>Melanin is brown, yellow-brown, or black color and is made by melanocytes . </li></ul><ul><li>Melanocytes are responsible for manufacturing and storing melanin and getting the pigment into the epithelial cells, thus causing a pigmentation. </li></ul>
  15. 15. Pigmentation Issues <ul><li>Freckles are bigger than normal amounts of melanin production. </li></ul><ul><li>Melanin can absorb UV light from the sun to prevent skin damage before it reaches deeper layers of the skin. </li></ul><ul><li>Despite this, cancers and sunburns can occur. </li></ul><ul><li>The epidermal cells are able to take these UV rays and convert them into vitamin D3 which is an essential hormone for the small intestine. </li></ul>Freckle production
  16. 16. Hair! The Basics <ul><li>Non-living structures that project above the skin. </li></ul><ul><li>Produced in hair follicles, which are considered organs. </li></ul><ul><li>An estimated 5 million on the body. </li></ul>
  17. 17. The Structure and Production of Hair <ul><li>Follicles reach into the dermis. </li></ul><ul><li>Formed by the repeated division of epithelial stem cells that surround the hair papilla (connective tissue that has capillaries and nerves) </li></ul><ul><li>Daughter cells pushed toward the surface of the skin, and the cells undergo keratinization and die. This is what forms the hair root (anchors hair into skin). We then see the hair. </li></ul>
  18. 18. Function of Hair <ul><li>Hair can guard entrances to places such as the nostrils and ear canals as well as the eyes. </li></ul><ul><li>A sensory nerve accompanies each hair so that one can prevent injury. </li></ul><ul><li>It can also provide a slight cushioning to the head. </li></ul>
  19. 19. Nails! <ul><li>Protect the tips of fingers and limit distortion when under stress. </li></ul><ul><li>Production occurs at the nail root (not visible to surface) </li></ul>
  20. 20. Structure of the Nail <ul><li>The nail body is dense mass consisting of dead keratinized cells; covers the nail bed. </li></ul><ul><li>The nail root is where all nail production occurs. </li></ul><ul><li>The cuticle extends over the nail that is exposed and is close to the root. </li></ul><ul><li>The light crescent is called the lunula . </li></ul><ul><li>Blood vessels under the nail give the nail its pink color. </li></ul>
  21. 21. Sebaceous Glands <ul><li>Oil glands that secrete an oily, waxy discharge into hair follicles or on the skin. </li></ul><ul><li>The secretion is called sebum. </li></ul><ul><li>Sebum lubricates skin and hair and starts the growth of bacteria. </li></ul><ul><li>Sebaceous follicles are the glands that excrete sebum onto the skin and are located on the back, face, chest, nipples, and male sex organs. </li></ul><ul><li>Sebaceous glands consist of sebaceous glands and sweat glands. </li></ul><ul><li>Is sensitive to hormones, thus one may develop acne if the glands become blocked. </li></ul>
  22. 22. Sweat Glands <ul><li>There are 2 types of sweat glands; apocrine and merocrine. </li></ul><ul><li>Apocrine sweat glands secrete around the groin, armpits, and nipples. </li></ul><ul><li>Merocrine sweat glands secrete onto the skin surface. </li></ul><ul><li>This is known as perspiration This cools a person down in order to maintain homeostasis in the body. </li></ul><ul><li>Bill Nye </li></ul>
  23. 23. Injury and Repair <ul><li>Stem cells replace lost epidermal and dermal cells. </li></ul><ul><li>Healing time depends on the severity of the wound. </li></ul><ul><li>There are 4 stages in repair. </li></ul>
  24. 24. The 4 Steps of Repair <ul><li>1. The injury site has mast cells and triggers an inflammatory response. </li></ul><ul><li>2. A scab forms to keep the wound safe. A scab is formed with fibrin (made by the body during clotting response. </li></ul><ul><li>3. Dermal repairs are done. Fibroblasts (fiber-producing cells) work on the deeper area of the wound. Capillaries follow these fibroblasts creating a blood supply. </li></ul><ul><li>4. Scar tissue forms from the fibrous tissue replacing hair follicles, glands, etc that cannot be repaired. The scab is also shed. </li></ul>
  25. 25. CLINICAL APPLICATIONS!
  26. 26. Diseases and Conditions <ul><li>Infections </li></ul><ul><li>Tumors </li></ul><ul><li>Trauma </li></ul><ul><li>Congenital disorders </li></ul><ul><li>Nutritional disorders </li></ul><ul><li>Degenerative disorders </li></ul><ul><li>Secondary disorders </li></ul><ul><li>Environmental stress and inflammation </li></ul>
  27. 27. Infections! <ul><li>Viral: </li></ul><ul><ul><li>Shingles: A viral infection that causes painful blisters on the skin in the path of peripheral sensory nerves. </li></ul></ul><ul><li>Bacterial </li></ul><ul><ul><li>Impetigo: A contagious skin infection that causes red sores that burst and rupture to form a yellowish-brown crust on the face around the nose and mouth. </li></ul></ul>http://apps.uwhealth.org/health/adam/graphics/images/en/19687.jpg http://www.adhb.govt.nz/newborn/TeachingResources/dermatology/BullousImpetigo/BullousImpetigo4.jpg
  28. 28. More Infections! <ul><li>Fungal: </li></ul><ul><ul><li> Ringworm: A contagious skin infection that often presents as itchy, red, scaly skin in a ring shape, surrounding a patch of unaffected skin. </li></ul></ul><ul><li>Parasitic: </li></ul><ul><ul><li>Pediculosis: This condition is commonly known as head lice. It can be asymptomatic, but more commonly, the patent develops small sores on the head as a result of scratching at the minute louse bites, four to six weeks after the initial transmission of the lice. </li></ul></ul>http://z.about.com/d/pediatrics/1/0/a/2/ringworm.jpg http://icb.usp.br/~marcelcp/Imagens/u14.jpg
  29. 29. Tumors! <ul><li>Basal Cell Carcinoma: </li></ul><ul><ul><li>Appears as a smooth, raised bump on skin that has frequently been exposed to the sun. It sometimes develops crusting and bleeding in its center, and can be mistaken for a common sore. </li></ul></ul><ul><li>Squamous Cell Carcinoma: </li></ul><ul><ul><li>Generally appears as a red, thick, scaly patch on sun-exposed skin. Ulcers and bleeding may appear, and left untreated, it could develop into a large mass. </li></ul></ul>
  30. 30. More Tumors! <ul><li>Malignant Melanoma: </li></ul><ul><ul><li>Appears frequently as brown or black lesions. Melanoma frequently can be mistaken for a mole that has changed in size, shape, color, or elevation, or a mole that is painful, itchy, or frequently bleeding. </li></ul></ul><ul><li>Kaposi’s Sarcoma: </li></ul><ul><ul><li>A slow-growing skin tumor that appears as multiple scattered bluish-brown nodules on sun-exposed areas. This type of tumor generally appears in patients with diabetes, lymphoma, and AIDS. </li></ul></ul>
  31. 31. Trauma! <ul><li>Wounds: </li></ul><ul><ul><li>Abrasions </li></ul></ul><ul><ul><li>Incisions </li></ul></ul><ul><ul><li>Lacerations </li></ul></ul><ul><ul><li>Contusions </li></ul></ul><ul><ul><li>Punctures </li></ul></ul><ul><ul><li>Avulsions </li></ul></ul><ul><li>Burns: </li></ul><ul><ul><li>First Degree </li></ul></ul><ul><ul><li>Second Degree </li></ul></ul><ul><ul><li>Third Degree </li></ul></ul>
  32. 32. Congenital Disorder: Albinism <ul><li>Albinism is a congenital lack of melanin in the body, which causes the skin, hair, and eyes to be nearly white. </li></ul><ul><li>Remember…melanin is one of the natural pigments found in the epidermis! </li></ul>http://www.cnb.uam.es/~montoliu/albinism.gif
  33. 33. Nutritional Disorder: Carotene Skin Color <ul><li>Carotene is an orange-yellow pigment naturally found in the epidermis. </li></ul><ul><li>Carotene can be derived from food sources such as carrots and squashes, and if Caucasians ingest an excessive amount of carotene, their skin can turn ORANGE from the pigments in the foods. </li></ul>http://z.about.com/d/pediatrics/1/0/L/P/carrots.jpg
  34. 34. Degenerative Disorder: Hair Loss <ul><li>Male-pattern baldness: As a result of changes in the level of sex hormones, hair production in the scalp changes from normal hair to very fine “peach fuzz”. </li></ul><ul><li>Alopecia areata: This condition presents itself as localized and temporary hair loss. There is no known cause and it is equally common in either sex, however some research suggests it could be related to immune disorders and high levels of stress. </li></ul>http://www.nlm.nih.gov/medlineplus/ency/images/ency/fullsize/17083.jpg http://www.tburg.k12.ny.us/starkweather/_Alopecia_areata_subtotalis.jpg
  35. 35. Degenerative Disorder: Xerosis <ul><li>DRY SKIN! </li></ul><ul><li>More common with advanced age </li></ul><ul><li>Caused by the degeneration of the cell membranes of the outer layers of skin </li></ul><ul><li>This makes skin rough, scaly, and more likely to perspire. </li></ul>http://thebeautybrains.com/wp-content/uploads/2006/10/dry-skin.jpg
  36. 36. Secondary Disorders! <ul><li>Secondary disorders are disorders that have side effects and symptoms that affect the integumentary system! </li></ul>
  37. 37. Secondary Disorder: Jaundice <ul><li>Presents itself as a yellow color in the skin and mucous membranes. </li></ul><ul><li>It frequently temporarily occurs in newborns </li></ul><ul><li>Also an indicator of compromised liver function. </li></ul>http://medicalimages.allrefer.com/large/jaundice.jpg
  38. 38. Secondary Disorder: Addison’s Disease <ul><li>Adrenal disorder </li></ul><ul><li>causes an insufficient amount of cortisol and aldosterone to be produced </li></ul><ul><li>Leads to difficulties maintaining normal blood glucose levels. </li></ul><ul><li>Common integumentary symptom of this disorder is a red blotchy pigmentation of the skin. </li></ul>
  39. 39. Secondary Disorder: Vitiligo <ul><li>Skin disorder that features white patches of skin on the face, backs of the hands, and armpits. </li></ul><ul><li>Patches can vary in size. </li></ul><ul><li>Michael Jackson? </li></ul>http://www.bagofnothing.com/wordpress/wp- content/uploads/2007/12/bwthomasap.jpg http://i6.photobucket.com/albums/y227/mitshu/vitiligo1.jpg http://i6.photobucket.com/albums/y227/mitshu/vitiligo1.jpg
  40. 40. Environmental Stress and Inflammation <ul><li>Hyperkeratosis: </li></ul><ul><ul><li>The excessive production of keratin in the body. </li></ul></ul><ul><ul><li>It appears as very thick calluses and corns on the skin. </li></ul></ul><ul><li>Decubitus ulcers: </li></ul><ul><ul><li>Bedsores </li></ul></ul><ul><ul><li>A type of abrasion created by unrelieved pressure on any part of the body </li></ul></ul>
  41. 41. Medical Procedures and Surgeries!
  42. 42. Options For Skin Surgery <ul><li>Electrosurgery </li></ul><ul><ul><li>The use of an electrical current to remove lesions, such as moles and cysts, from the skin. </li></ul></ul><ul><li>Cryosurgery (cryotherapy) </li></ul><ul><ul><li>The use of extremely cold temperatures and instruments to kill or remove unwanted cells, such as skin cancer or lesions such as warts. </li></ul></ul><ul><li>Traditional Surgery </li></ul><ul><ul><li>Ex. punch biopsy </li></ul></ul>
  43. 43. Diagnostic Tests <ul><li>Scraping off a sample of affected tissue (in the cases of fungal infections) </li></ul><ul><li>Culturing of fluid (to identify an infection and to determine how the infection would respond to a course of treatment.) </li></ul><ul><li>Biopsy of affected tissue (to observe the cellular structure: ex. Skin tumors) </li></ul><ul><li>Skin test (expose a localized area of the skin to an inactivated pathogen, ex. Intradermal TB test or patch testing for allergens) </li></ul>
  44. 44. Case Study!!! <ul><li>History of Present Illness: Bill Leonard, a 45 year old, red-haired, Caucasian surfer from Hawaii went to his physician because a friend noticed a dark brown spot on the back of his neck. Bill's doctor described the spot as a six-millimeter, dark brown, flat mole with smooth borders that appeared benign. Feeling very relieved, Bill did not think about the mole again until one year later when he went to his physician for a physical. At that visit, however, Bill's physician examined the lesion and suggested Bill see a dermatologist as soon as possible. </li></ul>
  45. 45. Case Study (Cont’d) <ul><li>Family History: No known history of any skin disorders. </li></ul><ul><li>Physical Examination: Normal except for the back, which showed the lesion had grown to 1.2 centimeters in diameter and was asymmetrical in shape. It was mainly dark brown, but had regions of a darker black hue along with some areas of light gray. The borders were irregular in outline. One of the blackened areas was slightly elevated. </li></ul><ul><li>(http://occawlonline.pearsoned.com/bookbind/pubbooks/mariebhap/chapter1/deluxe.html) </li></ul>
  46. 46. Related Career: Dermatology! http://www.hmc.psu.edu/dermatology/services/images/dermatology.gif
  47. 47. Dermatologists are… <ul><li>Physicians who have completed medical school, a one-year general residency, and a three-year dermatology residency. </li></ul><ul><li>Physicians who specialize in the conditions and diseases of the integumentary system. </li></ul><ul><li>Trained in dermatologic surgery </li></ul><ul><li>Knowledgeable about immunology, allergies, microbiology, and other fields that relate to dermatology through secondary disorders. </li></ul>
  48. 48. SURPRISE!!! Skin Grafts <ul><li>Skin grafts are areas of intact skin that are transferred to the site of a burn </li></ul><ul><li>Split-thickness graft: contains the superficial portions of the dermis and part of the epidermis </li></ul><ul><ul><li>Generally for first or second-degree burns </li></ul></ul><ul><li>Full-thickness graft: contains the epidermis and both layers of the dermis. </li></ul><ul><ul><li>Generally for third-degree burns </li></ul></ul>
  49. 49. BUT WAIT! There’s more… ARTIFICIAL SKIN! <ul><li>New treatment option for third-degree burns </li></ul><ul><li>Permanent dermal replacement layer: collagen from cow tendons and shark cartilage </li></ul><ul><li>Temporary epidermal replacement layer: silicone </li></ul><ul><li>Roughly one week post-implant (if it is not rejected), the body accepts the tissue and blood vessels and proteins begin to interact with the dermal layer </li></ul><ul><li>Two weeks post-implant, the silicone can be removed and replaced with a split-thickness graft from the patient. </li></ul>
  50. 50. SURPRISE AGAIN! Transdermal Medications <ul><li>Many conditions that do not directly affect the integumentary system are treated by transdermal medications. </li></ul>http://images.encarta.msn.com/xrefmedia/sharemed/targets/images/pho/t028/T028340A.jpg
  51. 51. Conditions Treated Transdermally <ul><li>Motion Sickness: scopolamine </li></ul><ul><li>Risk of Heart Attack: nitroglycerin </li></ul><ul><li>Menopause: estrogen </li></ul><ul><li>Cigarette Addiction: nicotine </li></ul><ul><li>High Blood Pressure: clonidine </li></ul><ul><li>Pain: fentanyl </li></ul>
  52. 52. Any Questions?
  53. 53. Works Cited!!!! <ul><li>Various. &quot;The Skin Project.&quot; Yankee Pot Roast 15 Oct 2008 <http://www.yankeepotroast.org/features/skin/1skin.jpg>. </li></ul><ul><li>Unknown. &quot;The Integumentary System.&quot; Biology Active Learner 15 Oct 2008 <http://www.dwm.ks.edu.tw/bio/activelearner/37/images/ch37c1.gif>. </li></ul><ul><li>Unknown. &quot;Basic Anatomy and Physiology of the Skin.&quot; Wildcrafted Herbal Products 15 Oct 2008 <http://www.wildcrafted.com.au/Image/Scetch%20Skin%20Secting.gif>. </li></ul><ul><li>Vann. &quot;07-08 Biology Worksheets.&quot; Head Royce School 14 MAY 2008 15 Oct 2008 <http://faculty.ircc.edu/faculty/tfischer/AP1/skin.jpg>. </li></ul><ul><li>Botzis , Ka. &quot;Sweating.&quot; Picture Book 20 AUG 2007 15 Oct 2008 <http://picture-book.com/files/userimages/244u/sweating.jpg>. </li></ul><ul><li>Grill, Jamie. &quot;Mother Placing Bandaid on Daughter's Knee .&quot; Corbis 15 Oct 2008 <http://pro.corbis.com/images/CBR002735.jpg?size=572&uid=%7BC3E95C33-64B2-487D-83B2-22FD81270740%7D>. </li></ul><ul><li>Various. &quot;Wound Repair and Regeneration.&quot; Nature 14 MAY 2008 15 Oct 2008 <http://www.nature.com/nature/journal/v453/n7193/images/nature07039-f1.0.jpg>. </li></ul>Willis, Bill. &quot;What Causes Freckles?.&quot; Worsley School 15 Oct 2008 <http://www.worsleyschool.net/science/files/freckles/diagram.gif>.
  54. 54. Works Cited Continued <ul><li>Martini, Bartholomew, Frederic, Edwin. Essentials of Anatomy and Physiology . Third. San Francisco: Pearson Education, Inc, 2003. </li></ul><ul><li>Unknown. &quot;Men's Hairstyles.&quot; Fashion Haircut Styles (2008) 15 Oct 2008 <http://z.about.com/d/mensfashion/1/5/P/3/ice_jason6_0030.jpg>. </li></ul><ul><li>Unknown. &quot;Hair Follicle.&quot; The Visual Dictionary 15 Oct 2008 <http://www.infovisual.info/03/037_en.html>. </li></ul><ul><li>Archana, V. &quot;Basic Nail Care.&quot; Talking My Thoughts 10 APR 2008 15 Oct 2008 <http://www.4ever8teen.co.uk/images/nails_14.jpg>. </li></ul><ul><li>Unknown. &quot;Integument.&quot; HistologyD502 27 OCT 2004 15 Oct 2008 <http://anatomy.iupui.edu/courses/histo_D502/D502f04/lecture.f04/integument.f04/nail.jpg>. </li></ul><ul><li>&quot;P&G Beauty Science.&quot; The World of Skin Care 15 Oct 2008 <http://www.pg.com/science/skincare/Skin_tws_34/skin_34_02.jpg>. </li></ul><ul><li>&quot;Affirmative Action.&quot; Race, Racism, and American Law 15 Oct 2008 <http://www.wvu.edu/~lawfac/jscully/Race/images/aa%20hands.jpg>. </li></ul>
  55. 55. Works Cited Continued… <ul><li>Badasch, Shirley A., and Doreen S. Chesebro. Health Science Fundamentals . Upper Saddle River, NJ: Prentice Hall, 2008. </li></ul><ul><li>Division of Parasitic Diseases (DPD), comp. &quot;Head Lice.&quot; CDC DPD . 12 May 2008. Department of Health and Human Services Centers for Disease Control and Prevention. 16 Oct. 2008 <http://www.cdc.gov/lice/head/index.html>. </li></ul><ul><li>Gerdin, B.S.N., M.S., Judith. Health Careers Today . 2nd ed. St.Louis, MO: Mosby-Year Book, Inc., 1997. </li></ul><ul><li>&quot;Impetigo.&quot; MayoClinic.com . 4 Oct. 2008. Mayo Clinic. 16 Oct. 2008 <http://www.mayoclinic.com/health/impetigo/ds00464>. </li></ul><ul><li>Lewis, M.D., F.A.A.P., Rachel A. &quot;Ringworm.&quot; MedlinePlus Medical Encyclopedia . 1 May 2007. U.S. National Library of Medicine and the National Institutes of Health. 16 Oct. 2008. </li></ul><ul><li>Youngson, Robert M., comp. Collins Dictionary of Medicine . 4th ed. London: HarperCollins, 2005. </li></ul>

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