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

rancid
(ran´sid) having a musty, rank taste or smell; applied to fats that have undergone decomposition, with the liberation of fatty acids.

random
(ran´dәm) pertaining to a chance-dependent process.

random pattern flap
a myocutaneous flap with a random pattern of arteries, as opposed to an axial pattern flap.

random sample
one in which each element of a population has the same chance of being selected, in the expectation of getting a representative sample so that generalizations can be made about the entire population. Called also probability sample.

random waves
brain waves showing irregular changes in potential and no fixed frequency.

randomization
(ran″dәm-ĭ-za´shәn) in a research study, the assignment of subjects to experimental (treatment) or control groups in such a way that each member of a sample has an equal chance of being assigned to a particular group. Random assignment ensures that the groups will be as alike as possible at ...

range
(rānj) the difference between the upper and lower limits of a variable or of a series of values. an interval in which values sampled from a population, or the values in the population itself, are known to lie. range of accommodation the total amount of accommodative pow...

ranine
(ra´nīn) pertaining to a frog. ranular. sublingual.

ranine artery
deep lingual artery.

ranine vein
sublingual vein.

ranitidine
(rә-nĭ´tĭ-dēn) an antagonist of histamine H2 receptors, used as the hydrochloride salt to inhibit stomach hydrochloric acid secretion in treatment of peptic ulcers, gastroesophageal reflux, and conditions of excessive stomach secretions; administered orally, intramuscularly, or intravenously.

rank sum test
a nonparametric statistical test for ordinal data, testing the null hypothesis that two samples are drawn from the same population versus the alternative hypothesis that the two samples are drawn from two populations having probability distributions of the same shape but different locations. It is based on the value of th...

ranula
(ran´u-lә) a cystic tumor beneath the tongue due to obstruction and dilatation of the sublingual or submaxillary gland or of a mucous gland. adj., ran´ular., adj.

rape
(rāp) sexual assault or abuse; sexual intercourse (usually vaginal or anal penetration) against the will and without the consent of the individual. acquaintance rape , date rape rape by someone known to the victim.

rape trauma syndrome
a group of symptoms caused by, or that are responses to, rape.

rapeseed oil
(rāp´sēd) the oil expressed from the seeds of the rapeseed plant; used in the manufacture of soaps, margarines, and lubricants. See also canola oil.

raphe
(ra´fe) a seam; anatomic nomenclature for the line of union of the halves of various symmetrical parts. abdominal raphe linea alba.

rapid eye movement
(REM) the rapid conjugate movement of the eyes that occurs during sleep; see discussion under sleep.

rapid eye movement sleep
REM sleep the period of sleep during which the brain waves are fast and of low voltage, and autonomic activities, such as heart rate and respiration, are irregular. This type of sleep is associated with dreaming, mild involuntary muscle jerks, and rapid eye movements. It usually occurs three to four times each night, at interval...

rapid filling wave
in the apexcardiogram, the steep positive deflection following the O point, or mitral valve opening, representing the period of rapid blood flow into the left ventricle. Its transition to the slow filling wave is marked by the third heart sound.

rapid plasma reagin test
(rap´id plaz´mah re´ah-jin) any of a group of flocculation tests, used in screening for syphilis, using a modified VDRL antigen. Called also RPR test.

rapid-acting insulin
an insulin preparation whose onset of action is from 0.5 to 1.5 hours after injection and peak of action is about 2 to 4 hours after injection. Examples include insulin (def. 3) and prompt insulin zinc suspension. Called also short-acting insulin.

Rapp-Hodgkin syndrome
(rap´ hoj´kin) anhidrotic ectodermal dysplasia.

rarefaction
(rar″ә-fak´shәn) the condition of being or becoming less dense.

rarefying osteitis
a bone disease in which the inorganic matter is diminished and the hard bone becomes cancellated.

rash
(rash) a temporary eruption on the skin. butterfly rash a skin eruption across the nose and adjacent areas of the cheeks in the pattern of a butterfly, as in lupus erythematosus and seborrheic dermatitis. See Atlas 2. diaper rash irritant dermatitis in the ...

rasp
(rasp) a coarse file used in surgery; called also raspatory. to file with such an instrument.

raspatory
(ras´pә-to-re) rasp (def. 1).

raspberry tongue
a diffusely reddened and swollen, uncoated tongue, as seen several days after the onset of the rash in scarlet fever.

RAST
radioallergosorbent test.

Rastelli operation
an operation for correction of large ventricular septal defects with pulmonary infundibular and valvular stenosis; an intraventricular patch is placed so that blood flows through the septal defect and out the aorta, and a prosthesis is placed to establish continuity between the right ventricle and the pulmonary artery.

rat mite dermatitis
that due to a bite of the rat-mite, Ornithonyssus bacoti.

rat typhus
murine typhus.

rat-bite disease
rat-bite fever either of two distinct diseases transmitted to humans by the bite of an infected rat or occasionally some other mammal. The type usually seen in North America is the bacillary or streptobacillary form, caused by Streptobacillus moniliformis. The type most often seen in East Asia and nearby islands is the spirillar...

rate
(rāt) the speed or frequency with which an event or circumstance occurs per unit of time, population, or other standard of comparison.

rate responsive pacemaker
an artificial cardiac pacemaker that can deliver stimuli at a rate adjustable to some parameter independent of atrial activity, such as respiratory rate, physical activity level, blood temperature, or mixed venous oxygen saturation level.

Rathke cysts
Rathke cleft cysts groups of epithelial cells forming small colloid-filled cysts in the pars intermedia of the pituitary gland; they are vestiges of Rathke's pouch and are closely related to craniopharyngiomas.

Rathke pouch
a diverticulum from the embryonic buccal cavity from which the adenohypophysis (anterior pituitary gland) is developed. Called also craniobuccal or craniopharyngeal pouch.

Rathke tumor
Rathke pouch tumor craniopharyngioma.

ratio
(ra´she-o) an expression of the quantity of one substance or entity in relation to that of another; the relationship between two quantities expressed as the quotient of one divided by the other.

rational
(ră´shәn-әl) based upon reason; characterized by possession of one's reason.

rationalization
(ră″shәn-әl-ĭ-za´shәn) a type of defense mechanism in which a person finds logical reasons (justification) for his or her behavior while ignoring the real reasons. It is a form of self-deception unconsciously used to make tolerable certain feelings, behaviors, and motives that would oth...

rattlesnake
(rat´әl-snāk) any of numerous pit vipers, venomous snakes of North America of the genera Crotalus and Sistrurus. See also snakebite.

rauwolfia
(rou-wool´fe-ә) any member of the genus Rauwolfia, tropical trees and shrubs. the dried root, or extract of the dried root, of one of these plants. rauwolfia serpentina the dried root of Rauwolfia serpentina, sometimes with fragments of rhizome and other parts, used as...

ray
(ra) a line emanating from a center. a distinct portion of electromagnetic radiation that proceeds in a specific direction.

Raygat test
hydrostatic test.

Raymond-Cestan syndrome
(ra-maw´ ses-tah´) a syndrome due to obstruction of twigs of the basilar artery causing lesions of the pontine region; it is characterized by quadriplegia, anesthesia, and nystagmus. Called also Cestan-Raymond syndrome and pontine syndrome.

Raynaud disease
(ra-no´) a condition in which spasm of the blood vessels causes symmetrical symptoms of the Raynaud phenomenon on both sides of the body, sometimes with local gangrene If left untreated, it may progress to ulceration and contractures. The cause is unknown; attacks are precipitated by cold or emotional upset and relieved...

Raynaud phenomenon
(ra-no´) intermittent attacks of ischemia of the fingers or toes, usually on both sides of the body at once, and sometimes on the ears or nose; characteristics include severe pallor, often with paresthesias and pain. It is brought on characteristically by cold or emotional stimuli and is relieved by heat. The cause is u...

Raynaud sign
acrocyanosis.

Rb
rubidium.

RBC
red blood cell; red blood cell count.

RBE
relative biological effectiveness.

rcp
reciprocal translocation.

RDA
recommended dietary allowance.

Re
rhenium.

reabsorb
(re″әb-sorb´) to absorb again; to undergo or to subject to reabsorption; to resorb.

reabsorption
(re″ab-sorp´shәn) the act or process of absorbing again, as the absorption by the kidneys of substances that were already secreted into the tubules, such as glucose, proteins, or sodium. resorption.

react
(re-akt´) to respond to a stimulus. to enter into chemical action.

reaction
(re-ak´shәn) opposite action or counteraction; the response of a part to stimulation. the phenomena caused by the action of chemical agents; a chemical process in which one substance is transformed into another substance or substances. in psychology, the mental or emotional state that d...

reaction of degeneration
the reaction to electrical stimulation of muscles whose nerves have degenerated, consisting of loss of response to a faradic stimulation in a muscle, and to galvanic and faradic stimulation in the nerve.

reaction time
the time elapsing between the application of a stimulus and the resulting reaction.

reaction-formation
(re-ak´shәn for-ma´shәn) a type of defense mechanism in which a person assumes an attitude that is the reverse of some infantile wish or impulse that he or she still feels.

reactivation tuberculosis
postprimary tuberculosis.

reactive
(re-ak´tiv) characterized by reaction; readily responsive to a stimulus.

reactive airways disease
any of several conditions characterized by wheezing and allergic reactions; the most common ones are asthma, bronchiolitis, and chronic obstructive pulmonary disease.

reactive arthritis
arthritis after an infection, such as urethritis caused by Chlamydia trachomatis or enteritis caused by Campylobacter, Salmonella, Shigella, or Yersinia. Cf. Reiter syndrome.

reactive attachment disorder
a mental disorder of infancy or early childhood characterized by notably unusual and developmentally inappropriate social relatedness, usually associated with grossly pathological care. It may be the inhibited type, with failure to initiate or respond to social interactions, or the disinhibited type, with indiscriminate sociabi...

reactive depression
a usually transient depression that is precipitated by a stressful life event or other environmental factor, in contrast to an endogenous depression.

reactive perforating collagenosis
(RPC) a rare, usually familial type of acquired perforating dermatosis in which collagen fibers are extruded through the epidermis. It occurs at sites of frequent trauma (e.g., the knees and backs of the hands) and is characterized by skin-colored papules with a central depression containing keratinous material. Lesions...

reactive systemic amyloidosis
secondary amyloidosis.

reactivity
(re″ak-tiv´ĭ-te) the process or property of being reactive.

reading
(rēd´ing) understanding of written or printed symbols representing words. lip reading , speech reading understanding of speech through observation of the speaker's lip movements.

reading chart
a chart with material printed in gradually increasing type sizes, used in testing acuity of near vision.

reading disorder
a learning disorder in which the skill affected is reading ability, including accuracy, speed, and comprehension.

reagent
(re-a´jәnt) a substance used to produce a chemical reaction so as to detect, measure, or produce other substances.

reagin
(re´ә-jin) antibody of a specialized type of immunoglobulin E that attaches to tissue cells of the same species from which it is derived, and interacts with its antigen to cause release of histamine and other vasoactive amines. A form of cytotropic antibody, it is present in the serum of naturally hypersensitive i...

real-time ultrasonography
B-mode ultrasonography using an array of detectors so that scans can be made electronically at a rate of 30 frames a second.

reamer
(rēm´әr) in root canal therapy, an engine-driven or hand-operated instrument for canal enlargement, consisting of a serrated triangular shaft twisted in a loose spiral.

rebound
(re´bound) a reversed response occurring upon withdrawal of a stimulus. acid rebound an increased rate of gastric acid secretion occurring 30 to 60 minutes after eating. heparin rebound the return of anticoagulant activity following neutralization of hepari...

rebound phenomenon
a manifestation of loss of coordination between groups of antagonistic muscles of the limbs in cerebellar dysfunction. It is usually tested by having the patient rest an elbow on a table and try to flex it against the resistance of the examiner; when the resistance is suddenly withdrawn, the affected arm rebounds to the p...

recanalization
(re-kan″ә-lĭ-za´shәn) formation of new canals or paths, especially blood vessels, through an obstruction such as a clot; called also canalization.

recapitulation theory
ontogeny recapitulates phylogeny, i.e., an organism, in the course of its development, goes through the same successive stages (in abbreviated form) as did the species in its evolutionary development.

receiving areas
receptive areas primary receiving areas.

recent memory
the ability to recall events from the immediate past.

receptaculum
(re″sәp-tak´u-lәm) Latin word meaning receptacle or container; a term used in anatomy receptaculum chyli cisterna chyli.

receptive
(re-cep´tiv) capable of receiving or of responding to a stimulus.

receptive aphasia
inability to understand written, spoken, or tactile speech symbols, due to disease of the auditory and visual word centers, as in word blindness. See also motor aphasia. Called also logamnesia and sensory or Wernicke's aphasia.

receptor
(re-sep´tәr) a molecule on or within a cell that recognizes and binds with specific molecules, producing some effect in the cell. One on the cell surface is called a cell-surface or membrane receptor, and one inside a cell (usually in its nucleus) is called a nuclear receptor. Examples are the cell-surface recepto...

recess
(re´ses) a small, empty space or cavity. epitympanic recess a small upper space of the middle ear, containing the head of the malleus and the body of the incus. Called also attic and epitympanum.

recession
(re-sesh´әn) the drawing away of a tissue or part from its normal position. gingival recession the drawing back of the gingivae from the necks of the teeth, with exposure of root surfaces.

recessive
(re-ses´iv) tending to recede. in genetics, pertaining to phenotypic expression of an allele only in homozygotes, i.e., when the allele is carried by both members of a pair of homologous chromosomes (or hemizygotes, for X-linked traits).

recessive allele
one that produces an effect (the phenotype) in the organism only when it is transmitted by both parents (the individual being homozygous). See also heredity.

recessive gene
recessive allele.

recessive trait
an inherited trait that is phenotypically expressed only when the mutant allele is present in the homozygous state. See also dominant trait.

recessus
(re-ses´әs) Latin word meaning recess; a term used in anatomy.

recidivation
(re-sid″ĭ-va´shәn) relapse, recurrence, or repetition, as of a disease or condition or of a pattern of behavior, particularly a criminal act.

recidivism
(re-sid´ĭ-viz-әm) a tendency to relapse into a previous condition, disease, or pattern of behavior, particularly a return to criminal behavior.

recidivist
(re-sid´ĭ-vist) a person who tends to relapse, especially one who tends to return to criminal habits after treatment or punishment.

recipe
(res´ĭ-pe) Latin word meaning take; used at the head of a prescription, and indicated by the symbol ℞. a formula for the preparation of a combination of ingredients.