Websters new world medical dictionary

TM Medical Dictionary Third Edition From the Doctors and Experts at WebMD Webster’s New World™ Medical Dictionary, Third Edition Copyright © 2008 MedicineNet.com All rights reserved Published by Wiley Publishing, Inc., Hoboken, New Jersey No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600, or on the web at www.copyright.com Requests to the Publisher for permission should be addressed to the Legal Department, Wiley Publishing, Inc., 10475 Crosspoint Blvd., Indianapolis, IN 46256, (317) 572-3447, fax (317) 572-4355, or online at http://www.wiley.com/go/permissions The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation warranties of fitness for a particular purpose No warranty may be created or extended by sales or promotional materials The advice and strategies contained herein may not be suitable for every situation This work is sold with the understanding that the publisher is not engaged in rendering legal, accounting, or other professional services If professional assistance is required, the services of a competent professional person should be sought Neither the publisher nor the author shall be liable for damages arising here from The fact that an organization or Website is referred to in this work as a citation and/or a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make Further, readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read Trademarks: Wiley, the Wiley Publishing logo, Webster’s New World, and all related trademarks, logos and trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc and/or its affiliates All other trademarks are the property of their respective owners Wiley Publishing, Inc is not associated with any product or vendor mentioned in this book For general information on our other products and services or to obtain technical support, please contact our Customer Care Department within the U.S at 800-762-2974, outside the U.S at 317-572-3993, or fax 317-572-4002 Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic books For more information about Wiley products, please visit our web site at www.wiley.com Library of Congress Cataloging-in-Publication Data is available from the publisher upon request ISBN: 978-0-470-18928-3 Printed in the United States of America 10 Book production by Wiley Publishing, Inc Composition Services TM Medical Dictionary Third Edition From the Doctors and Experts at WebMD Webster’s New World™ Medical Dictionary, Third Edition Copyright © 2008 MedicineNet.com All rights reserved Published by Wiley Publishing, Inc., Hoboken, New Jersey No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600, or on the web at www.copyright.com Requests to the Publisher for permission should be addressed to the Legal Department, Wiley Publishing, Inc., 10475 Crosspoint Blvd., Indianapolis, IN 46256, (317) 572-3447, fax (317) 572-4355, or online at http://www.wiley.com/go/permissions The publisher and the author make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation warranties of fitness for a particular purpose No warranty may be created or extended by sales or promotional materials The advice and strategies contained herein may not be suitable for every situation This work is sold with the understanding that the publisher is not engaged in rendering legal, accounting, or other professional services If professional assistance is required, the services of a competent professional person should be sought Neither the publisher nor the author shall be liable for damages arising here from The fact that an organization or Website is referred to in this work as a citation and/or a potential source of further information does not mean that the author or the publisher endorses the information the organization or Website may provide or recommendations it may make Further, readers should be aware that Internet Websites listed in this work may have changed or disappeared between when this work was written and when it is read Trademarks: Wiley, the Wiley Publishing logo, Webster’s New World, and all related trademarks, logos and trade dress are trademarks or registered trademarks of John Wiley & Sons, Inc and/or its affiliates All other trademarks are the property of their respective owners Wiley Publishing, Inc is not associated with any product or vendor mentioned in this book For general information on our other products and services or to obtain technical support, please contact our Customer Care Department within the U.S at 800-762-2974, outside the U.S at 317-572-3993, or fax 317-572-4002 Wiley also publishes its books in a variety of electronic formats Some content that appears in print may not be available in electronic books For more information about Wiley products, please visit our web site at www.wiley.com Library of Congress Cataloging-in-Publication Data is available from the publisher upon request ISBN: 978-0-470-18928-3 Printed in the United States of America 10 Book production by Wiley Publishing, Inc Composition Services Acknowledgments At MedicineNet.com, a part of the WebMD network, we continue to foster the concept that you, the readers, are truly interested in understanding health issues and medical concepts Accordingly, we have addressed the medical terms in this dictionary with sensitivity to potential concerns of those who are acutely or chronically confronting disease or health concerns We are grateful for your interest in health topics as it is a driving force for the development of the Webster’s New World Medical Dictionary, Third Edition On behalf of the MedicineNet.com division of WebMD, we wish to thank the staff at Wiley Publishing, Inc., especially Roxane Cerda and Suzanne Snyder, for bringing this dictionary to those who need it We also thank the officers of MedicineNet.com, particularly Gene Lu and David Sorenson, who have supported the development of this dictionary The excellence of the technical and editorial staffs at MedicineNet.com greatly facilitated this entire project Dan Griffith and Michael Cupp provided the unique publishing software that made it all possible Cynde Lee, Kelly McKiernan, and Tanya Buchanan have performed magnificently in managing the vast amount of content and communication between authors and editors David Sorenson has been an inspirational catalyst for motivation and consistent superior quality William C Shiel, Jr., MD, FACP, FACR, thanks his children, Cara Shiel Krenn, Daniel, and Timothy for their support He also acknowledges the support and encouragement of his parents, William and Virginia Shiel, as well as his dear mother-in-law, Helen Stark With infinite gratitude and love he thanks his wife, Catherine, for her support, love, and editing With gratitude he acknowledges the Herculean efforts of Frederick Hecht, MD, FAAP, FACMG in developing previous editions of this dictionary And, with admiration beyond words, he thanks his dear friend, colleague, and co-founder of MedicineNet.com, Dennis Lee, MD Melissa Conrad Stöppler, MD wishes to thank her husband, Hubert Stöppler, and her children, Johannes, Anna, and Tilman, for their enduring support, love, and patience She also gratefully acknowledges the support and encouragement of her parents, Kathryn B Conrad and the late Henry E Conrad, Jr Thank you all –William C Shiel, Jr., MD, FACP, FACR –Melissa Conrad Stöppler, MD Get Additional Free Content Online As an added bonus to this fully revised third edition of the Webster’s New World ™ Medical Dictionary, you can visit the companion website at www.medterms.com/wnw You’ll find a free PDF Healthcare Guide to help you get the most out of your personal medical care You can also listen to podcasts from Dr William Shiel and Dr Melissa Stöppler, the co-editors of the Webster’s New World Medical Dictionary, in which they discuss strategies to help you better communicate with your doctors and caregivers Editorial Staff Co-Editors-in-Chief William C Shiel, Jr., MD, FACP, FACR www.MedicineNet.com Melissa Conrad Stöppler, MD www.MedicineNet.com Assistant Editors Dennis Lee, MD www.MedicineNet.com Jay W Marks, MD www.MedicineNet.com Ruchi Mathur, MD, FRCP(C) www.MedicineNet.com Content Managers Cynde Lee Kelly McKiernan www.MedicineNet.com Concept Development David Sorenson Gene Lu www.MedicineNet.com About the Authors William C Shiel, Jr., MD, FACP, FACR, Co-Editor-in-Chief William C Shiel, Jr., MD, FACP, FACR, received a bachelor of science degree with honors from the University of Notre Dame There he was involved in research in radiation biology and received the Huisking Scholarship After graduating from St Louis University School of Medicine, he completed his internal medicine residency and rheumatology fellowship at University of California, Irvine He is board certified in internal medicine and rheumatology and is a fellow of the American Colleges of Physicians and Rheumatology Dr Shiel is in active practice in the field of rheumatology at the Arthritis Center of Southern Orange County, California He is currently an active associate clinical professor of medicine at University of California, Irvine He has served as chair of the Department of Internal Medicine at Mission Hospital Regional Medical Center in Mission Viejo, California Dr Shiel has authored numerous articles on subjects related to arthritis for prestigious peer-reviewed medical journals, as well as many expert medical-legal reviews He has lectured in person and on television both for physicians and the community He is a contributor for questions for the American Board of Internal Medicine and has reviewed board questions on behalf of the American Board of Rheumatology Subspecialty He served on the Medical and Scientific Committee of the Arthritis Foundation, and he is currently on the Medical Advisory Board of Lupus International Dr Shiel is proud to have served as chief editor for MedicineNet.com since its founding in 1996 He was co-editor-in-chief of the first and second editions of Webster’s New World Medical Dictionary Melissa Conrad Stöppler, MD, Co-Editor-in-Chief Melissa Conrad Stöppler, MD, is a US board-certified anatomic pathologist with subspecialty training in the fields of experimental and molecular pathology Dr Stöppler’s educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina She completed residency training in anatomic pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology Dr Stöppler served as a faculty member of the Georgetown University School of Medicine and has also served on the medical faculty at the University of Marburg, Germany Her research in the area of virusinduced cancers has been funded by the National Institutes of Health as well as by private foundations She has a broad list of medical publications, abstracts, and conference presentations and has taught medical students and residents both in the United States and Germany Dr Stöppler was named a fellow of the Alexander von Humboldt Society in Germany and was a recipient of a Physician Scientist Award from the US National Cancer Institute Dr Stöppler currently serves on the Medical Editorial Board of MedicineNet.com, and is the Chief Medical Editor of eMedicineHealth.com, both WebMD Inc companies Her experience also includes translation and editing of medical texts in German and English Dr Stöppler’s special interests in medicine include family health and fitness, patient education/empowerment, and molecular diagnostic pathology She currently resides in the San Francisco Bay area with her husband and their three children Dennis Lee, MD, Assistant Editor Dennis Lee, MD, was born in Shanghai, China, and received his college and medical training in the United States He is fluent in English and three Chinese dialects He graduated with chemistry departmental honors from Harvey Mudd College He was appointed president of AOA society at UCLA School of Medicine He underwent internal medicine residency and gastroenterology fellowship training at Cedars-Sinai Medical Center Board certified in internal medicine and gastroenterology, Dr Lee is currently a member of Mission Internal Medical Group, a multispecialty medical group serving southern Orange County, California Dr Lee has maintained an interest in technology and medical education He is a regular guest lecturer at Saddleback College in Orange County, California Dr Lee serves as chair of MedicineNet.com Jay W Marks, MD, Assistant Editor Jay W Marks, MD, is a board-certified internist and gastroenterologist He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles For 20 years he was associate director of the Division of Gastroenterology at Cedars-Sinai Medical Center and an associate professor of medicine, in residence, at UCLA At Cedars-Sinai he co-directed the Gastrointestinal Endoscopy Unit, taught physicians during their graduate and postgraduate training, and performed specialized, nonendoscopic gastrointestinal testing He carried out Public Health Service–sponsored (National Institutes of Health) clinical and basic research into mechanisms of the formation of gallstones and methods for the nonsurgical treatment of gallstones He is the author of 36 original research manuscripts and 24 book chapters Dr Marks presently directs an independent gastrointestinal diagnostic unit where he continues to perform specialized tests for the diagnosis of gastrointestinal diseases Dr Marks serves as medical and pharmacy editor of MedicineNet.com Ruchi Mathur, MD, FRCP(C), Assistant Editor Dr Mathur received her medical degree in Canada and did her medical residency at the University of Manitoba in Internal Medicine Dr Mathur is a certified fellow of the Royal College of Physicians of Canada and is US board certified in internal medicine and endocrinology, diabetes and metabolism She has been the recipient of numerous research grants which have included the American Diabetes Association grant for research in the field of diabetes and gastric dysmotility and the Endocrine Fellows Foundation Grant for Clinical Research She has an extensive list of medical publications, abstracts, and posters and has given numerous lectures on diabetes Most recently she has co-authored the textbook Davidson’s Diabetes Mellitus: Diagnosis and Treatment, published by Elsevier Dr Mathur has also served as Research Fellow at Cedars-Sinai Medical Center and a clinical instructor at UCLA in endocrinology and metabolism Currently Dr Mathur is Co-Director of the Diabetes Management Clinic at the Roybal Comprehensive Health Center and Assistant Professor of Medicine at the Keck School of Medicine, University of Southern California Contributing Authors Ronald Adamany, MD, Gastroenterology • Kent Adamson, MD, Orthopedic Surgery • Leon Baginski, MD, Obstetrics & Gynecology • Jerry Balentine, DO, FACOEP, FACEP, Emergency Medicine • Edward Block, MD, Gastroenterology • James Bredencamp, MD, Otolaryngology • Yuri Bronstein, MD, Neurology • Rudolph Brutico, MD, Pediatrics • Carolyn Janet Crandall, MD, Internal Medicine & Women’s Health • Howard Crystal, MD, Neurology • John Cunha, DO, Emergency Medicine • Eric Daar, MD, Internal Medicine & Infectious Diseases • Andrew A Dahl, MD, FACS, Opthamology • Werner-His disease RecQ DNA helicase, an enzyme that catalyzes the unwinding of DNA Werner-His disease See trench fever West Nile virus A febrile disease that is transmitted from birds to mosquitoes and then to people by mosquito bites The virus is named after the area in which it was first found, in Uganda West Nile virus occurs in parts of Africa and Asia and, infrequently, in Southern Europe, the Middle East, and the US West Nile virus had never been seen in birds or people in the Western Hemisphere prior to an outbreak in summer 1999 in New York City Since that time, it has spread across the US Most affected people have no symptoms or minor symptoms, but a febrile illness may develop accompanied by drowsiness, headache and nausea due to encephalitis, pain in the abdomen, a rash, and swollen glands (lymphadenopathy) Fatal cases tend to involve infants and small children under age 5, the aged, and people with impaired immune systems Prevention of mosquito bites can help prevent infection Also known as West Nile encephalitis See also encephalitis 456 Whipple disease A form of inability to absorb nutrients from the intestine It can affect any part of the body, leading to arthritis and then weight loss, cough, fever, diarrhea, hypotension (low blood pressure), abdominal swelling, increased skin pigmentation, and severe anemia Whipple disease has been discovered to be due to a type of bacteria named Tropheryma whippelii Whipple disease is treated with antibiotics Some patients relapse and need long-term, even life-long, treatment Whipple procedure A type of surgery that is used to treat pancreatic cancer and was devised by the US surgeon Allen Whipple The head of the pancreas, the duodenum, a portion of the stomach, and other nearby tissues are removed Western blot A technique in molecular biology that is used to separate and identify particular proteins whipworm A nematode (roundworm), also called Trichuris trichiura, that is the third most common roundworm in humans The whipworm is found worldwide, and whipworm infections are most frequent among children and in areas with tropical weather and poor sanitation practices Infection with whipworm most often occurs without symptoms Heavy infections, especially in small children, can cause gastrointestinal problems (such as abdominal pain, diarrhea, and rectal prolapse) and possibly growth retardation Treatment involves use of the drugs albendazole or mebendazole WF Medical shorthand for white female white blood cell See CBC; leukocyte Wharton’s jelly A gelatinous substance that provides insulation and protection within the umbilical cord Stem cells are present in Wharton’s jelly, as well as in umbilical cord blood white blood cell count The number of white blood cells (WBCs) in the blood The normal range for the WBC count varies among laboratories but is usually between 4,300 and 10,800 cells per cubic millimeter It can be expressed in international units as (4.3–10.8)×109 cells per liter A low WBC count is called leukopenia A high WBC count is termed leukocytosis Also known as leukocyte count wheezing A whistling noise in the chest during breathing Wheezing occurs when the airways are narrowed or compressed whiplash injury A hyperextension and flexion injury to the neck, often a result of being struck from behind, as by a fast-moving vehicle in a car accident The mechanics of whiplash injury are thought to be as follows: The victim may be first pushed or accelerated forward, pushing the body forward, but the head remains behind momentarily, rocking up and back, and some muscles and ligaments in and around the spine may be stretched or torn These muscles, in a reflex action, contract to bring the head forward again, to prevent excessive injury There may be overcompensation when the head is traveling in a forward direction as the vehicle decelerates This may rock the head violently forward, stretching and tearing more muscles and ligaments white coat hypertension A transient increase in blood pressure (hypertension) that is triggered by the sight of medical personnel in white coats (or other attire) Ideally, people so affected should their best to relax when in the medical office white matter The part of the brain that contains myelinated nerve fibers The white matter is white because it is the color of myelin, the insulation that covers nerve fibers white spots on the nails See jogger’s nails white subungual onychomycosis, proximal See onychomycosis, proximal white subungual 457 wormwood whitehead A familiar term for what is medically called a closed comedo A comedo, the primary sign of acne, consists of a dilated (widened) hair follicle filled with keratin squamae (skin debris), bacteria, and sebum (oil) A whitehead is a comedo that has an obstructed opening to the skin A closed comedo may rupture and cause a low-grade skin inflammatory reaction in the area is due to mutation of the ATP7B gene on chromosome 13 The ATP7B gene encodes ATPase, a copper-transporting beta polypeptide WHO World Health Organization wisdom tooth See tooth, wisdom whooping cough See pertussis withdrawal symptoms Abnormal physical or psychological features that follow the abrupt discontinuation of a drug that has the capability of producing physical dependence Common withdrawal symptoms include sweating, tremors, vomiting, anxiety, insomnia, and muscle pain will, living See living will Willis, circle of See circle of Willis Wilms tumor A childhood form of kidney cancer with a peak age of occurrence at years of age It is sometimes associated with abnormalities of the urinary tracts or other birth defects Some cases are related to defects in one of two genes referred to as Wilms’ tumor (WT1) or Wilms’ tumor (WT2) Symptoms can include abdominal pain, swelling, and blood in the urine Diagnosis is made by biopsy, which can classify the tumors as having a favorable histology (microscopic appearance) or an unfavorable histology, which is associated with a worse outcome The outcome is also reflected by the stage of the tumor (extent of spread) at the time of diagnosis Treatment involves surgery and chemotherapy; sometimes radiation therapy is also recommended Wilms tumor has a very high cure rate, particularly when detected as a localized tumor Also known as nephroblastoma Wilson disease An inherited disorder of copper metabolism that results in an abnormal accumulation of copper in the body Although the accumulation of copper begins at birth, symptoms of the disorder not appear until later in life, between the ages of and 40 A diagnostic feature of the disease is a Kayser-Fleischer ring, a deep coppercolored ring around the edge of the cornea that represents copper deposits in the eye The main clinical consequence of Wilson disease for most affected persons is liver disease In other patients the first symptoms are nervous system or psychiatric symptoms or both and include tremor, rigidity, drooling, difficulty with speech, abrupt personality change, grossly inappropriate behavior and inexplicable deterioration of school or other work, neurosis, and psychosis Without proper treatment, Wilson disease is always fatal, usually by age 30 If treatment is begun early enough, symptomatic recovery is usually complete, and a life of normal length and quality can be expected Wilson disease is inherited in an autosomal recessive manner and windpipe See trachea winter depression See seasonal affective disorder WM Medical shorthand for white male WNL Medical shorthand for within normal limits For example, a laboratory test result may be WNL Wolff-Parkinson-White syndrome A condition that is caused by an abnormality in the electrical system of the heart, which normally tells the heart muscle when to contract Abbreviated WPW syndrome In WPW syndrome there is an extra electrical connection inside the heart that acts as a short circuit, causing the heart to beat too rapidly and sometimes in an irregular manner WPW syndrome can be life threatening, although that is unusual WPW syndrome can be treated via destruction of the short circuit, using a technique termed radiofrequency catheter ablation, in which the short circuit is destroyed using radiofrequency energy Wolhynia fever See trench fever womb See uterus word processor’s cramp A dystonia that affects the muscles of the hand and sometimes the forearm and that occurs only during typing or use of a computer Similar focal dystonias have also been called writer’s cramp, pianist’s cramp, musician’s cramp, and golfer’s cramp working memory See memory, short-term World Health Organization The subagency of the United Nations (UN) that is concerned with international health Abbreviated WHO Also known as Organisation Mondiale de la Santé (OMS) wormwood The plant whose essence forms the basis of absinthe, a dangerous emerald-green liqueur See also absinthe WPW syndrome WPW syndrome Wolff-Parkinson-White syndrome wrist The part of the hand that is nearest the forearm and consists of the carpal bones and the associated soft tissues The eight carpal bones are arranged in two rows One row of carpal bones joins the long bones of the forearm (the radius, and, indirectly, the ulna) Another row of carpal bones meets the hand at the five metacarpal bones that make up the palm 458 writer’s cramp See cramp, writer’s wryneck See torticollis, congenital WS Waardenburg syndrome Wt Abbreviation for weight For example, “Wt 80 lbs” means “weight 80 pounds.” Xx X In genetics and medicine, X chromosome X chromosome The sex chromosome that is found twice in normal females and singly, along with a Y chromosome, in normal males The complete chromosome complement consists of 46 chromosomes, including the sex chromosomes, and is thus conventionally written as 46,XX for chromosomally normal females and 46,XY for chromosomally normal males xanthelasma Tiny, slightly raised, yellowish plaques on the skin surface of the upper or lower eyelids Xanthelasma is a harmless growth of tissue caused by tiny deposits of fat in the skin, and it is often associated with abnormal blood fat levels (hyperlipidemia) Xanthelasma is composed of lipid-laden foam cells called histiocytes Treatment is directed toward any underlying lipid disorder when present Dermatologists can remove the abnormal plaques See also xanthoma xanthinuria A rare metabolic disorder that is caused by lack of an enzyme needed to process xanthine, an alkaloid found in caffeine; theobromine; theophylline; and related substances Unchecked, xanthinuria can lead to kidney stone formation Treatment involves avoiding foods and drinks that contain xanthine derivatives, such as coffee, tea, and cola Classic xanthinuria is inherited in an autosomal recessive manner and involves a defect in the enzyme xanthine dehydrogenase xanthoma A firm yellow, orange, or brown nodule deep in the skin (such as around the Achilles tendon, elbows, or knees) or mucous membrane caused by fat deposition Although xanthomas themselves are harmless, they frequently indicate underlying disease, such as diabetes, lipid disorders (such as elevated blood cholesterol levels), or other conditions They are composed of lipid-laden foam cells called histiocytes Treatment is directed toward any underlying disorder when present The nodules can be resected surgically for cosmetic purposes Xanthoma is distinguished from xanthelasma by being a large nodule deep in the tissues as opposed to a plaque on the skin surface, but both can occur from lipid disorders See also xanthelasma xanthoma, diabetic Xanthoma that is associated with poorly controlled diabetes mellitus Treating the diabetes causes diabetic xanthomas to disappear xanthoma, eruptive Xanthoma that is linked to lipid disorders and is accompanied by a pink-to-red raised rash xanthoma, planar A type of xanthoma that is characterized by flat yellow-to-orange patches or pimples that cluster together on the skin xanthoma disseminatum A type of xanthoma from chronically elevated blood fats (cholesterol and triglycerides) that is characterized by orangeto-brown nodules on the skin or mucous membranes xanthoma tendinosum Xanthoma that clusters around tendons and is associated with lipid disorders, including chronically elevated blood cholesterol levels xanthoma tuberosum Xanthoma that clusters near joints and is associated with lipid disorders, cirrhosis of the liver, and thyroid disorders xanthomatosis An accumulation of excess lipids in the body that is due to disturbance of lipid metabolism and marked by the formation of xanthomas See also xanthoma xanthopsia A form of chromatopsia, a visual abnormality in which objects look as though they have been overpainted with an unnatural color In xanthopsia, that color is yellow xanthosis Yellowing of the skin without yellowing of the eyes, as is seen in jaundice XDR-TB See tuberculosis, extensively drugresistant xenotransplantation Transplantation from one species to another (for example, from a baboon to a human) xero- Prefix indicating dryness, as in xeroderma (dry skin) xeroderma Abnormally dry skin Xeroderma can be caused by a deficiency of vitamin A, systemic illness (such as hypothyroidism or Sjogren’s syndrome), overexposure to sunlight, and medication Xeroderma can usually be addressed with the use of over-the-counter topical preparations xeroderma pigmentosum A genetic disease that is characterized by such extraordinary sensitivity to sunlight that it results in the development of skin cancer at a very early age Abbreviated XP Children xerophagia with XP can only play outdoors safely after nightfall XP is due to defective repair of damage done to DNA by ultraviolet (UV) light Whereas normal persons can repair UV-induced damage by inserting new bases into the DNA, XP patients cannot A person with XP develops severe sunburn and eye irritation within minutes of exposure to sunlight Other features of XP include very dry skin (xeroderma), blisters on the skin, heavy freckling, and dark spots on the skin XP is inherited in an autosomal recessive manner Defects in multiple genes have been identified that lead to XP Avoiding UV light and using the highest level of sunscreen possible when exposure cannot be avoided helps prevent complications xerophagia Having a tendency to eat a dry diet xerophthalmia Dry eyes Xerophthalmia can be associated with systemic diseases, such as Sjogren’s syndrome, systemic lupus erythematosus, and rheumatoid arthritis; deficiency of vitamin A; and use of some medications It results from inadequate function of the lacrimal glands, which produce tears When xerophthalmia is due to vitamin A deficiency, the condition begins with night blindness and conjunctival xerosis (dryness of the eye membranes), progresses to corneal xerosis (dryness of the cornea), and in its late stages develops into keratomalacia (softening of the cornea) Treatment depends on the severity of the condition and ranges from artificial tears and ointments to plugging of the tear ducts Also known as conjunctivitis arida xerosis Abnormal dryness of the skin, mucous membranes, or conjunctiva (xerophthalmia) There are many causes of xerosis, and treatment depends on the particular cause xerostomia Dry mouth Xerostomia can be associated with systemic diseases, such as Sjogren’s syndrome, systemic lupus erythematosus, and rheumatoid arthritis; and it can be a side effect of medication and poor dental hygiene Xerostomia results from inadequate function of the salivary glands, such as the parotid glands Treatment involves adequate intake of water, use of artificial saliva, and good dental care Untreated, severe dry mouth can lead to increased levels of tooth decay and thrush xiphoid process The lower part of the breastbone The xiphoid process has no particular function and ranges in size from miniscule to several inches in length X-linked A gene on the X chromosome that is located on the X chromosome An X-linked disorder is associated with or caused by a gene on the X chromosome 460 X-linked dominant An X-linked trait that is expressed when one copy of the gene for that trait is present In the case of an X-linked dominant disease, a single copy of the mutant gene on the X chromosome can cause the disease in a female An example is a type of hereditary rickets called hypophosphatemic rickets See also autosomal dominant trait; X-linked recessive X-linked recessive A mode of genetic inheritance characterized by a gene on the X chromosome being expressed only when there is no different gene present at that spot (locus) on a second X chromosome This means that X-linked traits are expressed in males and in females who are homozygous for the gene (they have a copy of the particular gene on each of their two X chromosomes) For example, Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder A boy with DMD has the DMD gene on his sole X chromosome Although it is much rarer, a girl can have the DMD gene on both her X chromosomes and have DMD See also autosomal recessive trait; X-linked dominant X-ray High-energy radiation with waves shorter than those of visible light X-ray is used in low doses to make images that help to diagnose diseases and in high doses to treat cancer X-ray, AP An X-ray picture in which the beams pass through the patient anteroposteriorly (from front to back) X-ray, lateral An X-ray picture that is taken from the side X-ray, PA An X-ray picture in which the beams pass through the patient posteroanteriorly (from back to front) X-ray therapy The use of X-ray radiation to treat cancer X-rays may be used inside or outside the body, depending on the type of tumor involved See also radiation therapy XX The sex chromosome complement of a normal human female See also X chromosome XXX syndrome A chromosome condition that is present in in 1,000 females, due to the presence of three X chromosomes rather than the usual two The condition is associated with increased height but no malformations Intelligence ranges from above normal to mild mental retardation Also known as triple X and triplo-X XY The most frequent sex chromosome complement in human males See also X chromosome; Y chromosome 461 xylitol A sweetener that is found in plants and used as a substitute for sugar Xylitol is called a nutritive sweetener because it provides calories, just like sugar However, it is less likely than sugar to contribute to dental caries XYY syndrome XYY syndrome A chromosomal disorder that affects about in 1,000 males caused by the presence of an extra Y chromosome Symptoms may include increased height, speech delays, learning disabilities, mild to moderate mental retardation, and behavioral disturbances Also known as polysomy Y syndrome Yy Y In chemistry, the symbol for the element yttrium, an extremely rare metal that has been used in certain nuclear medicine scans In genetics, the Y chromosome Y chromosome The sex chromosome that is found, together with an X chromosome, in most normal males The Y chromosome contains the unique male-determining gene and the male fitness genes that are active only in the testis and are responsible for the formation of sperm Other genes on the Y chromosome have counterparts on the X chromosome, are active in many body tissues, and play crucial “housekeeping” roles with the cell Y chromosome sex-determining region The region on the Y chromosome that decides the sex of the individual Abbreviated SRY SRY is necessary for male determination It encodes the testis-determining factor Mutations in SRY are responsible for XY females with gonadal dysgenesis who appear to be normal females at birth but at puberty not develop secondary sexual characteristics (such as breasts), not menstruate, and have scarred (fibrous) gonads without eggs Y map The array of genes on the Y chromosome yard A measurement of length that is equal to 0.9 meters, feet, or 36 inches yawn Involuntary opening of the mouth, accompanied by slowly breathing inward and then outward Repeated yawning can be a sign of drowsiness, boredom, or depression The yawn helps to open tiny air sacs (alveoli) in the lungs that can collapse during shallow breathing yaws A chronic infectious disease that occurs commonly in the warm, humid regions of the tropics Yaws is characterized by bumps on the skin of the face, hands, feet, and genital area Almost all cases of yaws are in children under 15 years of age The organism that causes yaws is a type of spirochete bacteria, Treponema pertenue, which enters the skin at a scraped or cut spot after contact with an infected person A painless bump (the mother yaw) arises and grows at this spot Nearby lymph nodes may become swollen The mother yaw is followed by recurring (secondary) crops of bumps and more swollen lymph nodes In its late (tertiary) stage, yaws can destroy and deform areas of the skin, bones, and joints The palms and soles tend to become thickened and painful (“dry crab yaws”) Diagnosis is confirmed via blood tests and via dark-field examination of the spirochete under a microscope Treatment involves administration of antibiotics Also known as granuloma tropicum, polypapilloma tropicum, and thymiosis yd Yard yeast A group of single-celled fungi that reproduce by budding Most yeast is harmless, and yeast is commonly present without ill effect on normal human skin and mucous membranes, including the gastrointestinal (GI) tract In the GI tract, the amount of yeast is usually controlled by helpful bacteria, although this balance can be upset by illness, immune system problems, or antibiotic use Extreme overproliferation of yeast can cause discomfort and disease For example, the common yeast Candida albicans (once called Monilia) causes thrush and rashes, fingernail infections, vaginal infections, and a host of other problems in patients with immune deficiency See also Candida albicans; candidiasis; thrush; yeast infection; yeast rash yeast diaper rash Infection in the diaper area of a baby that is caused by a yeast called Candida Certain conditions, such as antibiotic use or excessive moisture, can upset the balance of microbes and allow an overgrowth of Candida The infected skin is usually fiery red with areas that may have a raised red border yeast infection Overgrowth of yeast that affects the skin (yeast rash), mouth (thrush), digestive tract, esophagus, vagina (vaginitis), or other parts of the body Yeast infections occur most frequently in moist areas of the body Although Candida albicans and other Candida yeasts are the most frequent offenders, other yeast groups are known to cause illness, primarily in immunocompromised patients Diagnosis is confirmed by culturing a stool or mucosa sample or a scraping from the affected area Treatment involves use of topical or oral antifungal medications See also Candida albicans; candidiasis; thrush; yeast vaginitis; yeast rash yeast rash A slightly raised pink-to-red rash that is caused by proliferation of yeast, usually in a moist area such as the groin Yeast rash is most common in infants, but it can also occur on the skin of older children and adults Treatment involves keeping the affected area clean and dry and applying topical antifungal medication Also known as diaper dermatitis and nappy rash yeast vaginitis yeast vaginitis Infection of the vagina by Candida albicans, which characteristically causes itching, burning, soreness, pain during intercourse and urination, and vaginal discharge Yeast vaginitis occurs when new yeast are introduced into the vagina or when the quantity of yeast in the vagina increases relative to the quantity of bacteria Yeast vaginitis can be exacerbated by injury to the vagina, as from chemotherapy; immune deficiency, as from AIDS or cortisone-type medications; pregnancy or taking birth control pills; antibiotic use; or diabetes Treatment involves use of topical or oral antifungal medications See also Candida albicans; yeast; yeast infection; yeast vulvitis yeast vulvitis A yeast infection of the vulva Yeast vulvitis commonly occurs with yeast vaginitis Common symptoms include itching, burning, soreness, pain during intercourse and urination, and vaginal discharge Treatment involves use of topical or oral antifungal medications See also Candida albicans; yeast; yeast infection; yeast vaginitis yellow fever An acute, systemic viral illness transmitted to humans through the bite of infected mosquitos that may cause a flu-like illness or a more severe illness with high fever, bleeding into the skin, and death of cells (necrosis) in the kidney and liver The liver damage (hepatitis) causes yellowing of the skin from severe jaundice Yellow fever occurs in sub-Saharan Africa and tropical South America Diagnosis is made via observation and, if necessary, culturing or examining blood samples Yellow fever usually passes within a few weeks Nonaspirin pain relievers, rest, and rehydration with fluids decrease discomfort Yellow fever disease can be prevented with a vaccination See also yellow fever vaccination yellow fever vaccination A live attenuated (weakened) viral vaccine for yellow fever Yellow fever vaccination is recommended for people traveling to or living in the tropical areas in the Americas and Africa where yellow fever occurs Because yellow fever vaccination is a live vaccine, it should not be given to infants or people with immune-system problems yellow jacket stings Stings from yellow jackets that can trigger allergic reactions of varying severity Avoidance and prompt treatment of allergic reactions (including diphenhydramine, brand name: 464 Benadryl; and epinephrine, brand name: Epi-Pen) are essential In selected cases, allergy injection therapy is highly effective for prevention Yersinia A family of bacteria that includes Yersinia pestis, which causes the bubonic, pneumonic, and septicemic plagues; Y entercolitica, which causes intestinal infections, including mesenteric lymphadenitis, a condition that mimics appendicitis; and Y pseudotuberculosis, which usually adversely affects only animals but can cause illness in immunocompromised patients Both Y entercolitica and Y pseudotuberculosis have also been implicated in a viral form of arthritis Infection with Yersinia bacteria can be treated with antibiotics See also plague Y-linked A gene on the Y chromosome that is passed from father to son See also holandric inheritance Y-linked inheritance See holandric inheritance yoga A relaxing form of exercise that was developed in India and involves assuming and holding postures that stretch the limbs and muscles, doing breathing exercises, and using meditation techniques to calm the mind Yoga appears to have benefits for increasing physical flexibility and reducing internal feelings of stress Yoga may be recommended as an alternative or complementary healthpromoting practice yogurt Milk that is fermented with a culture of Lactobacillus (the milk bacillus) and often with acidophilus and other helpful bacteria See also probiotic yolk bone See zygoma yolk sac The membrane outside the human embryo The yolk sac is connected by a tube, the yolk stalk or omphalomesenteric duct, through the umbilical opening to the embryo’s midgut The yolk sac serves as an early site for the formation of blood, and in time it is incorporated into the primitive gut of the embryo yolk stalk See omphalomesenteric duct youth The time between childhood and maturity Zz Z chromosome A sex chromosome in certain animals, such as chickens, turkeys, and moths In humans, males are XY and females are XX, but in animals with a Z chromosome, males are ZZ and females are WZ zebra In medicine, a very unlikely diagnostic possibility It comes from an old saying used in teaching medical students about how to think logically in regard to the differential diagnosis: “When you hear hoof beats, think of horses, not zebras.” For example, when someone develops a mild transient cough, a virus infection is the most logical and likely cause, and tuberculosis is a zebra Zellweger syndrome One of a group of related diseases called peroxisome biogenesis disorders (PBD), inherited conditions that damage myelin in the brain and also affect the metabolism of particular substances Features include enlargement of the liver, high levels of iron and copper in the blood, and vision disturbances It can be caused by mutations in a number of different genes There is no cure for Zellweger syndrome The prognosis is poor, with death usually occurring within months Zenker diverticulum The most common type of outpouching in the esophagus, due to increased pressure causing the mucous membrane of the esophagus to herniate through a defect in the wall of esophagus Zenker diverticuli are usually located in the posterior hypopharyngeal wall Small Zenker diverticuli may not cause symptoms but larger ones may collect food and obstruct the esophagus ZIFT See zygote intrafallopian transfer zinc A mineral that is essential to the body and is a constituent of many enzymes that permit chemical reactions to proceed at normal rates Zinc is involved in the manufacture of protein (protein synthesis) and in cell division Zinc is also a constituent of insulin, and it is involved with the sense of smell Food sources of zinc include meat, particularly liver and seafood; eggs; nuts; and cereal grains zinc acetate A form of zinc that has been used in zinc supplements zinc deficiency See deficiency, zinc zinc excess Too much zinc, which can cause gastrointestinal irritation, interfere with copper absorption to cause copper deficiency and, like too little zinc, cause immune deficiency See also zinc zinc ointment A topical preparation that contains zinc and is applied to protect the skin from irritation or sunburn Zinc ointment is also often the basis for commercial preparations for preventing diaper rash It should not be used on skin that is already broken or irritated, however zinc oxide A form of zinc that has been used in zinc ointments zinc sulfate A form of zinc that can be administered in eyedrops Zinc sulfate is used in some types of eye tests Zinsser disease See Brill-Zinsser disease Zollinger-Ellison syndrome A rare disorder caused by a tumor called a gastrinoma, most often occurring in the pancreas The tumor secretes the hormone gastrin, which causes increased production of gastric acid leading to severe recurrent ulcers of the esophagus, stomach, and the upper portions of the small intestine Gastrinomas resulting in the Zollinger-Ellison syndrome may also occur in the stomach, duodenum, spleen, and lymph nodes Treatment can include the use of H2 antagonist medications, proton pump inhibitors, or surgical removal of the tumor zona pellucida The strong membrane that forms around an ovum as it develops in the ovary The membrane remains in place during the egg’s travel through the fallopian tube To fertilize the egg, a sperm must penetrate the thinning zona pellucida If fertilization takes place, the zona pellucida disappears, to permit implantation in the uterus zoonosis An infection that is known in nature to infect both humans and lower vertebrate animals zooparasite A living parasite, such as a worm or protozoa zoophilia A sexual disorder (paraphilia) that involves an abnormal desire to have sexual contact with animals See also paraphilia zygoma The bone that forms the prominence of the cheek Also known as zygomatic bone, zygomatic arch, malar bone, and yoke bone zygomatic arch See zygoma zygomatic bone See zygoma zygomycosis A potentially fatal, dangerous infection that is caused by various fungi from the class Zygomycetes Zygomycosis is seen most often in zygote patients who are already ill with diseases that suppress the immune system, such as AIDS, burn patients, patients taking corticosteroids, and those with poorly controlled diabetes If unchecked, the fungal infection can spread to the lungs and other organs, the blood, the eyes, and the brain Treatment involves controlling the underlying condition and attacking the infection with antifungal medications zygote The cell that is formed by the union of a male sex cell (sperm) and a female sex cell (an ovum) The zygote develops into the embryo, as instructed by the genetic material within the unified cell The unification of a sperm and an ovum is called fertilization See also ovum; sperm 466 zygote intrafallopian transfer An assisted reproductive procedure for the treatment of infertility in which a woman’s eggs are removed and fertilized with sperm in the laboratory, and the fertilized egg (zygote) is placed into the fallopian tube using a laparoscopic procedure Abbreviated ZIFT Like IVF and GIFT, ZIFT involves stimulation of the ovaries to produce multiple eggs and aspiration of the eggs See also GIFT; IVF zygotic lethal gene See gene, zygotic lethal Appendix A Prescription Abbreviations Prescriptions are the traditional means by which a physician permits patients to obtain certain medications and/or supplies from pharmacies The word prescription is derived from the Latin prae, meaning “before,” and scribere, meaning “to write.” This reflected the fact that a prescription had to be written before a drug could be prepared and administered to a patient A number of abbreviations, many derived from Latin terms, are used on prescription forms and medication labels These include the following: ad lib Use as much as one desires, or use at one’s own discretion From the Latin term ad libitum p.r.n Take as necessary or when needed From the Latin term pro re nata a.c Before meals From the Latin term ante cibum q.d Take once per day From the Latin term quaque die b.i.d Twice a day From the Latin term bis in die q.h Take once every hour From the Latin term quaque (every) and the abbreviation for hours cap Capsules da or daw Dispense as written q.i.d Take four times per day From the Latin term quater in die g, gm, or G Gram q.2h Take once every hours gtt Drops From the Latin term guttae q.3h Take once every hours h Hour q.4h Take once every hours mg Milligram tabs Tablets ml Milliliter t.i.d Take three times per day From the Latin term ter in die p.c Take after meals From the Latin term post cibum p.o Take by mouth, orally From the Latin term per os ut dict Take as directed From the Latin term ut dictum Drug Caution Codes Drug caution codes are abbreviations that are applied to medications to indicate caution Drug caution codes provide valuable warnings to patients and their families They include both universal codes that apply to all patients and specific caution codes that apply under certain circumstances In the US, a system of stickers with pictographs may also be used to warn of specific side effects, such as drowsiness Patients who see one of these codes on their prescriptions should talk to a pharmacist before using the medications Universal Caution Codes D Drowsiness H Habit forming I Interaction X S.O.S (contains a substance, such as acetaminophen, that could cause problems; consult a pharmacist) Specific Caution Codes A ASA (contains acetylsalicylic acid [aspirin]) G Glaucoma C Caution S Diabetes These code letters are cautions for patients with specific medical problems A person with a medical problem, such as high blood pressure, might see the generic “C” code on a prescription bottle if the medication could raise his or her blood pressure Appendix B Anatomic Orientation Terms In anatomy, certain terms are used to denote orientation For example, a structure may be horizontal, as opposed to vertical Commonly used anatomic orientation terms include the following: anterior The front, as opposed to posterior For example, the breastbone is part of the anterior surface of the chest anteroposterior From front to back, as opposed to posteroanterior Abbreviated AP For example, when a chest X-ray is taken with the patient’s back against the film plate and the X-ray machine in front of the patient, it is referred to as an AP view ascending Going upward For example, the ascending aorta is the portion of the aorta that ascends, going upward as it leaves the heart to form the beginning of the arch of the aorta caudad Toward the feet (or tail, in embryology), as opposed to cranial cranial Toward the head, as opposed to caudad midline An imaginary line down the middle of posterior The back or behind, as opposed to anterior posteroanterior From back to front, as opposed to anteroposterior Abbreviated PA pronation Rotation of the forearm and hand so that the palm is down (or similar movement of the foot and leg, with the sole down), as opposed to supination prone With the front or ventral surface downward (lying face down), as opposed to supine proximal Toward the beginning, as opposed to distal deep Away from the exterior surface or farther into the body, as opposed to superficial sagittal A vertical plane that passes through the standing body from front to back For example, the midsaggital, or median, plane splits the body into left and right halves descending Going down For example, the descending aorta is the portion of the aorta that descends, going downward from the top of the arch of the aorta superficial On the surface or shallow, as opposed to deep distal Farther from the beginning, as opposed to proximal dorsal The back, as opposed to ventral external Situated on the outside extra Prefix indicating outside of horizontal Parallel to the floor; a plane that passes through the standing body parallel to the floor inferior Below, as opposed to superior internal Situated on the inside superior Above, as opposed to inferior supination Rotation of the forearm and hand so that the palm is upward (or similar movement of the foot and leg, with the sole upward), as opposed to pronation supine With the back or dorsal surface downward (lying face up), as opposed to prone transverse A horizontal plane that passes through the standing body parallel to the ground valgus Deformed Opposite of varus varus Deformed Opposite of valgus outward inward from midline toward midline intra prefix indicating within lateral Toward the left or right side of the body, as opposed to medial ventral Pertaining to the abdomen, as opposed to dorsal vertical Upright, as opposed to horizontal medial In the middle or inside, as opposed to lateral Appendix C Vitamins The term vitamin was coined in 1911 by the Warsaw-born biochemist Casimir Funk Working at the Lister Institute in London, Funk isolated a substance that prevented nerve inflammation (neuritis) in chickens raised on a diet deficient in that substance He named the substance “vitamine” because he believed it was necessary to life and it was a chemical amine The e at the end was later removed when it was recognized that vitamins need not be amines Vitamins soon became identified, as they were noted to be associated with vitamin deficiency diseases The letters (A, B, C, and so on) were assigned to the vitamins in the order of their discovery The one exception was vitamin K, which was assigned its K (from Koagulation) by the Danish researcher Henrik Dam Vitamins are known to play a major role in both health maintenance and the treatment of certain diseases The classic vitamins are divided into two categories, oil-soluble and water-soluble, based on how they are absorbed with the food we eat The oil-soluble vitamins are vitamins A, D, E, and K and are absorbed with fats There are nine water-soluble vitamins, thiamine (vitamin B1), riboflavin (vitamin B2), pyridoxine (vitamin B6), cyanocobalamin (vitamin B12), ascorbic acid (vitamin C), biotin, folic acid, niacin, and pantothenic acid Other vitamins have more recently been described and are included below Beta carotene is a plant pigment that is a precursor of vitamin A Vitamins can be dangerous in overdose The vitamins include: ascorbic acid Vitamin C nicotinic acid Vitamin B3 beta carotene Not actually a vitamin but a plant pigment that is a precursor of vitamin A Beta carotene is an antioxidant that protects cells against oxidative damage that may predispose a person to cancer Beta carotene is converted to the oil-soluble vitamin A, as needed Food sources include vegetables such as carrots, sweet potatoes, and spinach and other leafy green vegetables; and fruits such as cantaloupes and apricots Excessive carotene can temporarily yellow the skin, an innocuous condition called carotenemia that is commonly seen in infants who have been fed large amounts of mashed carrots pantothenic acid Vitamin B5 bioflavinoid Vitamin P biotin Vitamin H calciferol Vitamin D2 cholecalciferol Vitamin D3 cobalamin Vitamin B12 folic acid A member of the water-soluble, B vitamin family that is essential for cell growth and proliferation and for the proper utilization of vitamin B12 and vitamin C Folic acid is an important factor in nucleic acid (RNA and DNA) synthesis It is found in leafy green vegetables, liver and other organ meats, and whole grains Deficiency of folic acid can lead to slow growth, diarrhea, oral inflammation, a decrease in all types of blood cells (pancytopenia), and megaloblastic anemia (anemia with abnormally large red blood cells) Inadequate folic acid during pregnancy raises the risk of neural tube defects in the fetus and of miscarriages Also known as folate Nonpregnant adults require 200 micrograms of folic acid per day For pregnant women, typically mg daily is recommend in the form of prenatal multivitamins niacin Vitamin B3 pyridoxine Vitamin B6 retinol Vitamin A riboflavin Vitamin B2 thiamin Vitamin B1 vitamin A An oil-soluble vitamin that is also known as retinol Carotene compounds are gradually converted by the body to vitamin A A form of vitamin A called retinal is responsible for transmitting light sensations in the retina of the eye Vitamin A is found in egg yolk, butter, cream, leafy green vegetables, yellow fruits and vegetables, cod-liver oil, and similar fishliver oils Deficiency of vitamin A leads to night blindness and to diseases that affect the eyes and mucous membranes Overdose of vitamin A can cause insomnia, joint pain, fatigue, irritability, headache, and other symptoms The daily adult requirement is 900 micrograms vitamin A2 A form of vitamin A that is found only in the flesh of freshwater fish vitamin B1 Thiamin, a water-soluble vitamin, which acts as a coenzyme and is essential for a number of reactions in body metabolism Vitamin B1 is found primarily in liver and yeast, and it is easily destroyed by cooking Deficiency of vitamin B1 leads to beriberi, a disease of the heart and nervous system The daily adult requirement is 1.2 milligrams vitamin B2 Riboflavin, a water-soluble vitamin, which is a component of two coenzymes in the oxidation-reduction processes that are important to body metabolism Vitamin B2 is found primarily in liver and yeast, and it is easily destroyed by cooking Deficiency of vitamin B2 causes inflammation of the lining of the mouth and skin The daily adult requirement is 1.5 milligrams vitamin B3 vitamin B3 Niacin, a water-soluble vitamin, which is a component of coenzymes that are important in body metabolism Vitamin B3 is found primarily in liver and yeast, and it is easily destroyed by cooking Deficiency of vitamin B3 causes inflammation of the skin, vagina, rectum, and mouth, as well as mental slowing Also known as nicotinic acid The daily adult requirement is 16 milligrams vitamin B5 Pantothenic acid, a water-soluble, B vitamin that is widely distributed in nature Pantothenic acid is virtually ubiquitous It is present in foods as diverse as poultry, soybeans, yogurt, and sweet potatoes No naturally occurring disease due to a deficiency of vitamin B5 has been identified, due to the ease of obtaining this vitamin An experimental deficiency of pantothenic acid has, however, been created by administering an antagonist to pantothenic acid This experiment produced disease, thereby demonstrating that pantothenic acid is essential to humans 470 thesis in the skin Vitamin D is added to many common dairy products and breads, and it can also be found in saltwater fish and egg yolks Deficiency can lead to osteomalcia (softening of bone) in adults and bone deformity (rickets) in children The daily adult requirement is 10 micrograms vitamin D2 Calciferol, a synthetic form of vitamin D that is created by treating ergosterol (provitamin D2) with ultraviolet light waves Vitamin D2 is important in normal bone metabolism Vitamin D2 is largely supplied by the metabolism of vitamin D in the body vitamin D3 Cholecalciferol, a D vitamin that is needed for proper use of phosphorus, calcium, and vitamin A It plays a steroid-like role in regulating cellular proliferation and differentiation Vitamin D3 is important in normal bone metabolism Also known as calcitrol Vitamin D3 is largely supplied by the metabolism of vitamin D in the body vitamin B6 Pyridoxine, a water-soluble vitamin, which is a cofactor for enzymes Vitamin B6 is found primarily in liver and yeast, and it is easily destroyed by cooking Deficiency of vitamin B6 leads to inflammation of the skin and mouth, nausea, vomiting, dizziness, weakness, and anemia The daily adult requirement is milligrams vitamin E An oil-soluble vitamin that is vital for muscle, skin, blood vessel, and organ development and function Dietary sources for vitamin E include nuts, nut and corn oils, wheat germ, liver, sweet potatoes, and green leafy vegetables Deficiency of vitamin E can lead to anemia The daily adult requirement is 10 milligrams vitamin B12 Cobalamin, a water-soluble vitamin, which is an essential factor in nucleic acid synthesis Vitamin B12 may affect vitamin C absorption It is found primarily in liver and yeast, and it is easily destroyed by cooking Deficiency of vitamin B12 leads to megaloblastic anemia, as can be seen in pernicious anemia The daily adult requirement is micrograms vitamin H Biotin, which is actually considered part of the water-soluble, B vitamin family It is a coenzyme essential for many enzyme functions Normally produced by bacteria in the colon, biotin is also found in yeast, organ meats, legumes, egg yolks, whole grains, and nuts The daily adult requirement is 60 micrograms vitamin C Ascorbic acid, a water-soluble vitamin that is important in the synthesis of collagen, the framework protein for tissues of the body Vitamin C is found in citrus fruits, tomatoes, berries, potatoes, and most vegetables It may affect vitamin B12 absorption Minor deficiency can cause gum bleeding, joint pain, nosebleeds, and easy bruising Extreme deficiency can lead to scurvy, characterized by fragile capillaries, poor wound healing, and bone deformity in children Overdose is not possible with this water-soluble vitamin, but overuse can cause diarrhea, painful urination, rash, and nausea The daily adult requirement is 60 milligrams vitamin D An oil-soluble steroid vitamin that promotes absorption and metabolism of calcium and phosphorus and that is essential for tooth and bone growth Under normal conditions of sunlight exposure, no dietary supplementation is necessary because sunlight promotes adequate vitamin D syn- vitamin K An oil-soluble vitamin essential to the normal clotting of blood Vitamin K is normally made within the body by intestinal bacteria, but it is also found in many foods, including leafy green vegetables, yogurt, egg yolk, and fish-liver oils Deficiency may occur following the administration of drugs that inhibit the growth of the vitamin-synthesizing bacteria or as a result of disorders affecting the production or flow of bile necessary for the intestinal absorption of vitamin K In newborn babies, the absence of intestinal bacteria coupled with the absence of body stores of vitamin K may result in hemorrhagic disease of the newborn This is a dangerous condition because there can be bleeding into critical organs such as the brain This disorder can be prevented by the administration of vitamin K to the baby shortly after birth or to the mother during labor Daily adult requirement is 65 micrograms vitamin P Bioflavinoids, a group of substances found with and essential to the use of vitamin C They are essential for building collagen and capillary walls, among other functions ... online medical dictionary that now contains a wealth of contemporary medical terms and provides the broad foundation for this book To create this new edition of Webster’s New World Medical Dictionary, ... Wiley Publishing, Inc Composition Services TM Medical Dictionary Third Edition From the Doctors and Experts at WebMD Webster’s New World? ?? Medical Dictionary, Third Edition Copyright © 2008 MedicineNet.com...TM Medical Dictionary Third Edition From the Doctors and Experts at WebMD Webster’s New World? ?? Medical Dictionary, Third Edition Copyright © 2008 MedicineNet.com