Copy of `Dorland's Medical Dictionary`

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Dorland's Medical Dictionary Category: Health and Medicine > Medical Dictionary Date & country: 31/12/2010, USA Words: 39128

rhodopsin
(ro-dop´sin) visual purple: a photosensitive purple-red chromoprotein in the retinal rods that is bleached to visual yellow (all-transretinal) by light, thereby stimulating retinal sensory endings. Lack of rhodopsin results in night blindness. Vitamin A is the primary source of rhodopsin.

RhoGAM
(ro´gam) trademark for a preparation of Rh0 (D antigen) immune globulin. The gamma globulin is derived from the plasma of women previously immunized to the Rh0 (D) antigen and is administered after each Rh-incompatible pregnancy. The gamma globulin prevents the formation of antibodies after delivery or abortion. See als...

rhombencephalon
(rom″ben-sef´ә-lon) the portion of the brain developed from the most caudal of the three primary brain vesicles of the early embryo, comprising the metencephalon and myelencephalon. the most caudal of the three primary vesicles formed in embryonic development of the brain, which later divides i...

rhombocoele
(rom´bo-sēl) the terminal expansion of the canal of the spinal cord.

rhomboid
(rom´boid) shaped like a rectangle that has been skewed to one side so that the angles are oblique.

rhomboid ligament
rhomboid ligament of clavicle a ligament connecting the cartilage of the first rib to the undersurface of the clavicle.

rhomboid major muscle
origin, spinous processes of second, third, fourth, and fifth thoracic vertebrae; insertion, medial margin of scapula; innervation, dorsal scapular nerve; action, retracts, elevates scapula.

rhomboid minor muscle
origin, spinous processes of seventh cervical to first thoracic vertebrae, lower part of nuchal ligament; insertion, medial margin of scapula at root of the spine; innervation, dorsal scapular nerve; action, adducts, elevates scapula.

rhotacism
(ro´tә-sizm) a speech disorder consisting of imperfect pronunciation of the r sound. Called also pararhotacism.

Rhus
(rus) the sumacs, a genus of trees and shrubs that are mostly native to North America. Contact with certain species produces allergic contact dermatitis that is often severe. The most important poisonous species are R. ra´dicans (poison ivy), R. diversilo´ba (western poison oak), R. toxicoden´dron (eastern poison oak), and R....

rhus dermatitis
Rhus dermatitis allergic contact dermatitis due to exposure to plants of the genus Rhus, which includes poison ivy, poison oak, and poison sumac.

rhythm
(rith´әm) a measured movement; the recurrence of an action or function at regular intervals. adj., rhyth´mic, rhyth´mical., adj.

rhythm method
old popular name for natural family planning.

rhythmic movement disorder
repetitive, rhythmic, stereotyped, large-muscle body or head movements occurring during the transition to sleep, such as in jactatio capitis nocturna; onset is usually in infancy and the disorder is usually outgrown by the age of five.

rhythmicity
(rith-mis´ĭ-te) in cardiology, the ability to beat, or the state of beating, rhythmically without external stimuli.

rhytid
(ri´tid) pl. rhy´tides a wrinkle in the skin.

rhytidectomy
(rit″ĭ-dek´tә-me) plastic surgery for the removal of wrinkles, done to make an aging face look younger. The usual procedure is to open skin flaps near the ears in order to undermine the skin of the cheeks and jaws; this can be done with incisions adjacent to or within the hairline so that the scar...

rhytidoplasty
(rit´ĭ-do-plas″te) rhytidectomy.

rhytidosis
(rit″ĭ-do´sis) a wrinkling, as of the cornea.

RIA
radioimmunoassay.

rib
(rib) any of the paired bones, 12 on either side, extending from the thoracic vertebrae toward the median line on the ventral aspect of the trunk, forming the major part of the thoracic skeleton. Called also costa.

ribavirin
(ri″bә-vi´rin) a nucleoside analogue that acts as a broad-spectrum antiviral; used in treatment of severe viral pneumonia caused by respiratory syncytial virus, particularly in high-risk infants with underlying conditions such as cardiopulmonary disease; administered by oral inhalation. It is also used in co...

ribitol
(ri´bĭ-tol) a sugar alcohol formed by reduction of the carbonyl group of ribose; it is a constituent of a class of teichoic acids.

riboflavin
(ri´bo-fla″vin) vitamin B2. riboflavin kinase a phosphotransferase enzyme that catalyzes the conversion of free riboflavin and ATP to flavin mononucleotide and ADP.

ribonuclease
(ri″bo-noo´kle-ās) an enzyme that catalyzes the depolymerization of ribonucleic acid.

ribonucleic acid
(ri″bo-noo-kle´ik) RNA.

ribonucleoprotein
(RNP) (ri″bo-noo″kle-o-pro´tēn) a complex of protein and RNA (ribonucleic acid). small nuclear ribonucleoprotein(snRNP) any of a group of ribonucleoproteins, each composed of a small nuclear RNA (snRNA) associated with approximatel...

ribonucleoside
(ri″bo-noo´kle-o-sīd) a nucleoside in which the purine or pyrimidine base is combined with ribose.

ribonucleotide
(ri″bo-noo´kle-o-tīd) a nucleotide in which the purine or pyrimidine base is combined with ribose.

ribose
(ri´bōs) 5-carbon sugar present in ribonucleic acid (RNA).

ribosomal RNA
(rRNA) the most abundant type of RNA, which together with proteins makes up the ribosomes. It is involved in the process of linking of amino acids to form protein molecules (translation).

ribosome
(ri´bo-sōm) any of the intracellular ribonucleoproteinorganelles concerned with protein synthesis, found either bound to cell membranes or free in the cytoplasm. They may occur singly or in clusters (polyribosomes). The genetic code is translated when ribosomes attach to messenger RNA.

ribosyl
(ri´bo-sәl) a glycosyl radical formed from ribose.

ribozyme
(ri´bo-zīm″) an RNA molecule with catalytic activity; different classes exist, and the reactions they catalyze may be intramolecular, such as self-splicing, or intermolecular, such as processing of transfer RNA molecules.

rice bodies
small bodies resembling grains of rice which form in the tendons of joints and in the fluid of hygroma; called also oryzoid bodies and corpora oryzoidea.

rice disease
beriberi.

rice field fever
leptospirosis in workers in rice fields.

Richards-Rundle syndrome
(rich´әrdz run´dәl) a congenital syndrome consisting of ketoaciduria, mental retardation, underdevelopment of secondary sex characteristics, deafness, ataxia, and peripheral muscular wasting which progresses during childhood but eventually becomes static.

Richner-Hanhart syndrome
(rik´nәr hahn´hahrt) type II tyrosinemia.

Richter hernia
an incarcerated or strangulated hernia in which less than all of the circumference of the intestinal wall is involved.

Richter syndrome
(rik´tәr) chronic lymphocytic leukemia with diffuse histiocytic lymphoma.

ricin
(ri´sin) a phytotoxin in the seeds of the castor oil plant (Ricinus communis), inhalation or ingestion of which causes intoxication, producing superficial inflammation of the respiratory mucosa with hemorrhages into the lungs, or edema of the gastrointestinal tract with hemorrhages.

ricinus oil
castor oil.

rickets
(rik´әts) a condition seen most often in children, caused by deficiency of vitamin D, which leads to altered calcium and phosphorus metabolism. The major symptom is softening of the bones, which can produce various degrees of deformity in children, and inability of the bones to support or protect the body normally...

Rickettsia
(rĭ-ket´se-ә) a genus of bacteria made up of small, gram-negative, rod-shaped to coccoid microorganisms that multiply only inside host cells. They are found inside tissue cells or free-floating in the intestines of lice, fleas, ticks, and mites, which transmit them when they bite larger animals. R. cono...

rickettsia
(rĭ-ket´se-ә) pl. rickett´siae An individual organism of the family Rickettsiaceae.

Rickettsiaceae
(rĭ-ket″se-a´se-e) a family of bacteria of the the order Rickettsiales.

rickettsial
(rĭ-ket´se-әl) pertaining to or caused by rickettsiae.

rickettsial endocarditis
infectious endocarditis caused by invasion of the heart valves with Coxiella burnetii; it is a sequela of Q fever, usually occurring in persons who have had rheumatic fever.

Rickettsiales
(rĭ-ket″se-a´lēz) an order of bacteria comprising small, gram-negative, rod-shaped or coccoid, often pleomorphic microorganisms occurring as elementary bodies that typically multiply only inside the cells of the host. Found as parasites in both vertebrates and invertebrates, which may serve as vect...

rickettsialpox
(rĭ-ket´se-әl-poks″) a febrile disease marked by a vesiculopapular eruption, resembling chickenpox clinically, caused by Rickettsia akari and transmitted by mites.

rickettsicidal
(rĭ-ket″sĭ-si´dәl) lethal to rickettsiae; see also antirickettsial.

Riddoch mass reflex
mass reflex.

Ridell operation
obliteration of the frontal sinus by removal of the anterior wall and floor and sometimes posterior walls of the sinus; for treatment of malignant tumors.

rider's bone
localized ossification sometimes seen on the inner side of the lower end of the tendon of the adductor muscle of the thigh in horseback riders.

ridge
(rij) a linear projection or projecting structure, such as a crest.

Riedel disease
(re´del) Riedel thyroiditis a chronic type of autoimmune thyroiditis with a proliferating, fibrosing, inflammatory process involving usually one but sometimes both lobes of the gland, which becomes hard and enlarged and adherent to the trachea and other adjacent structures.

Riedel lobe
an anomalous tongue-shaped mass of tissue that sometimes projects from the right lobe of the liver.

Rieder cell
a myeloblast seen in a type of acute myelogenous leukemia (Rieder cell leukemia) and chronic lymphocytic leukemia; it has a nucleus with wide and deep indentations suggesting lobulation, which may represent asynchronism of nuclear and cytoplasmic maturation. Called also Rieder lymphocyte.

Rieder cell leukemia
a form of acute myelogenous leukemia in which the blood contains Rieder cells, asynchronously developed lymphocytes that have immature cytoplasm and a lobulated, indented, comparatively more mature nucleus.

Riegel pulse
a pulse that decreases during respiration.

Rieger anomaly
(re´gәr) a developmental anomaly consisting of posterior embryotoxon, hypoplasia of iris stroma, and usually glaucoma.

Rieger phenomenon
(re´gәr) brake phenomenon.

Rieger syndrome
(re´gәr) Rieger anomaly accompanied by hypodontia, anal stenosis, hypertelorism, mental deficiency, and agenesis of the facial bones. See also anterior chamber cleavage syndrome.

Riesman sign
Snellen sign. softening of the eyeball in diabetic coma.

rifabutin
(rif″ә-bu´tin) an antibacterial used for the prevention of disseminated Mycobacterium avium complex disease in patients with advanced HIV infection; administered orally.

rifampicin
(rif´am-pĭ-sin) rifampin.

rifampin
(rif-am´pin) a semisynthetic derivative of rifamycin, with the antibacterial actions and uses of the rifamycin group; administered orally or intravenously.

rifamycin
(rif″ә-mi´sin) any of a family of antibiotics biosynthesized by a strain of Streptomyces mediterranei, effective against a broad spectrum of bacteria. The five components are designated A, B, C, D, and E; rifamycins O, S, and SV are derivatives of the B component, and AG and X are derivatives of the O compon...

rifapentine
(rif″ә-pen´tēn) a synthetic rifamycin antibiotic used in treatment of pulmonary tuberculosis, administered orally.

rifaximin
(rif-ak´sĭ-min) a semisynthetic derivative of rifamycin, administered orally for the treatment of traveler's diarrhea caused by noninvasive strains of Escherichia coli.

Rift Valley fever
(rift´ val´e) a viral disease of southern and eastern Africa that occurs in sheep and cattle and can be transmitted to humans. It is caused by a species of Phlebovirus and is spread to humans by a mosquito bite or by contact with infected animals. In humans, it ranges in severity from a mild, influenzalike illness...

Rift Valley fever virus
a virus of the genus Phlebovirus that causes Rift Valley fever in humans and other animals.

Riga-Fede disease
(re´gah fa´da) a small sublingual ulceration in infants with natal or neonatal teeth due to rubbing the lower central incisors; most often observed in whooping cough.

Riggs disease
(rigz) marginal periodontitis.

right atrial veins of heart
the smallest cardiac veins emptying into the right atrium of the heart.

right atrioventricular orifice
tricuspid orifice.

right bundle branch block
(RBBB) see bundle branch block.

right colic artery
origin, superior mesenteric artery; branches, none; distribution, ascending colon.

right colic flexure
the angular junction of the ascending and transverse colon.

right colic vein
a vein that follows the path of the right colic artery and empties into the superior mesenteric vein.

right coronary artery
origin, right aortic sinus; branches, conus artery and atrial, atrioventricular node, intermediate atrial, posterior interventricular, right marginal, and sinoatrial node branches; distribution, right ventricle, right atrium.

right coronary catheter
one designed for coronary arteriography of the right coronary artery.

right coronary vein
the portion of the middle cardiac vein that receives blood from the posterior interventricular vein and empties into the coronary sinus.

right gastric artery
origin, common hepatic artery; branches, none; distribution, lesser curvature of stomach.

right gastric vein
a vein following the path of the right gastric artery and emptying into the portal vein.

right gastro-omental artery
origin, gastroduodenal artery; branches, gastric, omental branches; distribution, stomach, greater omentum.

right gastro-omental vein
a vein that follows the path of the right gastro-omental artery and empties into the superior mesenteric vein.

right gastroepiploic artery
right gastro-omental artery.

right gastroepiploic vein
right gastro-omental vein.

right heart bypass
diversion of the flow of blood from the entrance of the right atrium directly to the pulmonary arteries, avoiding the right atrium and right ventricles.

right hepatic vein
the large hepatic vein that drains the central veins in the right side of the liver and empties into the inferior vena cava.

right inferior pulmonary vein
a vein that returns blood from the lower lobe of the right lung (from the superior segmental and common basal veins) to the left atrium of the heart.

right lobe of liver
traditional name for the largest of the four lobes of the liver, separated from the left lobe by the falciform ligament. It is bordered in the rear by the caudate and quadrate lobes.

right lymphatic duct
a vessel draining lymph from the upper right side of the body, receiving lymph from the right subclavian, jugular, and mediastinal trunks when those vessels do not open independently into the right brachiocephalic vein.

right marginal artery
a branch of the right coronary artery passing toward the apex of the heart along the acute margin of the heart and branching over the right ventricle.

right marginal vein
a vein ascending along the right margin of the heart, draining adjacent parts of the right ventricle and opening into the right atrium or anterior cardiac veins.

right ovarian vein
a vein that drains the right pampiniform plexus of the broad ligament and empties into the inferior vena cava.

right pulmonary artery
origin, pulmonary trunk; branches, numerous, named according to the segments of the lung to which they distribute unaerated blood; distribution, right lung.

right superior intercostal vein
a common trunk formed by union of the second, third, and sometimes fourth posterior intercostal veins, which drains into the azygos vein.