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Medical Dictionary


reactivation (re′ak-ti-va′shun)
1. Restoration of the lytic activity of an inactivated serum by means of the addition of complement. 2. Restoration of activity in an inactivated enzyme.

reactivity (re-ak-tiv′i-te)
1. The property of reacting, chemically or in any other sense. 2. The process of reacting.

reading (red′ing)
1. The perception and understanding of the meaning of visual symbols ( e.g., letters or words) by the scanning of writing or print with the eyes. 2. Any of several alternative ways of interpreting symbols, such as Braille or the close observation of a speaker's facial movements. lip r. SYN: speech r.. speech r. used by people with hearing impairment of nonauditory clues as to what is being said through observing the speaker's facial expressions, lip and jaw movements, and other gestures. SYN: lip r..

reading frame
The grouping of nucleotides by threes into codons. See frame-shift mutation. blocked r. a sequence of DNA that cannot be translated into a viable protein; usually due to the interruption by one or more termination codons. SYN: closed r.. closed r. SYN: blocked r.. open r. a gene presumed to code for a protein but for which no gene product has been identified; also known as unidentified r.. SYN: unidentified r.. unidentified r. (URF) SYN: open r..

readthrough (red′throo)
In molecular biology, transcription of a nucleic acid sequence beyond its normal termination sequence.

reagent (re-a′jent)
Any substance added to a solution of another substance to participate in a chemical reaction. [Mod. L. reagens] amino acid r. a r. used in the identification and quantification of amino acids. Benedict-Hopkins-Cole r. magnesium glyoxalate, made from a mixture of oxalic acid and magnesium, used for testing proteins for the presence of tryptophan. biuret r. an alkaline solution of copper sulfate. Cleland r. SYN: dithiothreitol. diazo r. two solutions, one of sodium nitrite, the other of acidified sulfanilic acid, used in bringing about diazotization. SYN: Ehrlich diazo r.. Dische r. Dische reaction. Dische-Schwarz r. r. used in the colorimetric detection of RNA. Drabkin r. a solution used in the cyanmethemoglobin method of measuring hemoglobin. It consists of sodium bicarbonate, potassium cyanide, and potassium ferricyanide. Dragendorff r. a r. used in the detection of alkaloids. Edlefsen r. an alkaline permanganate solution used in the determination of sugar in the urine. Edman r. SYN: phenylisothiocyanate. Ehrlich diazo r. SYN: diazo r.. Erdmann r. a mixture of sulfuric and nitric acids, used in testing alkaloids. Esbach r. picric acid, citric acid, and water (in the proportions 1, 2, and 97) used for the detection of albumin in the urine. Exton r. 50 g of sulfosalicylic acid and 200 g of Na2SO4&chmpnt;10H2O in a liter of water, used as a test for albumin. Fehling r. SYN: Fehling solution. Folin r. SYN: Folin reaction. Fouchet r. a 25% solution of trichloroacetic acid, containing 0.9% ferric chloride; a drop of the r. added at the surface line of barium chloride-impregnated filter paper that has been dipped in urine for 10 s will give a green color if bilirubin is present. SEE ALSO: Fouchet stain. Froehde r. sodium molybdate in strong sulfuric acid; this r. gives various color reactions with alkaloids. Frohn r. bismuth subnitrate (1.5) and water (20.0) heated to boiling, to which hydrochloric acid (10.0) and potassium iodide (7.0) are added; used to test for alkaloids and for sugar. Girard r. the hydrazine of betaine chloride, used to extract ketonic steroids by forming water-soluble hydrazones with them. Günzberg r. phloroglucin and vanillin used as a r. in Günzberg test. Hahn oxine r. an alcoholic solution of 8-hydroxyquinoline used in the determination of zinc, aluminum, magnesium, and other minerals. Hammarsten r. a mixture of 1 part 25% solution of nitric acid and 19 parts 25% solution of hydrochloric acid; the addition of a few drops to a mixture of 1 part of this r. and 4 parts alcohol will give a green color if bile is present. Ilosvay r. sulfanilic acid 0.5, dissolved in dilute acetic acid 150, mixed with naphthylamine 1, and dissolved in boiling water 20; the blue sediment that forms is dissolved in dilute acetic acid 150; a few drops of this r. added to water, saliva, or other fluid to be tested will produce a red color if nitrites are present. Kasten fluorescent Schiff reagents fluorescent analogs of Schiff r. that are fluorescent basic dyes lacking acidic side groups and containing one or more primary amine groups; used in cytochemical detection of DNA in Kasten fluorescent Feulgen stain, polysaccharides in Kasten fluorescent PAS stain, and proteins in the ninhydrin-Schiff stain; such analogs include acriflavine, auramine O, and flavophosphine N. Lloyd r. precipitated aluminum silicate, used in the determination of alkaloids. Mandelin r. a solution of ammonium vanadate in sulfuric acid, used in color tests for alkaloids. Marme r. a solution of potassium iodide and cadmium iodide used in testing for alkaloids. Marquis r. a solution of formaldehyde in sulfuric acid used in color tests for formaldehyde. Mecke r. a solution of selenous acid in sulfuric acid, used for color tests of alkaloids. Meyer r. a solution of phenolphthalein with sodium hydroxide, in water (glass-distilled); in the presence of minute traces of blood, the solution becomes purple or blue-red. Millon r. mercuric nitrate and nitric acid as used in the Millon reaction. Nessler r. a solution of potassium hydroxide, mercuric iodide, and potassium iodide; it yields a yellow color with ammonia (a brown precipitate with larger amounts) that can be used for quantitative assay. Rosenthaler-Turk r. a solution of potassium arsenate in sulfuric acid used in obtaining color tests for various opium alkaloids. Sanger r. SYN: fluoro-2,4-dinitrobenzene. Schaer r. an alcoholic or aqueous solution of chloral hydrate used as an extraction medium in investigations of alkaloids. Scheibler r. a solution of sodium tungstate in phosphoric acid used in tests for alkaloids. Schiff r. an aqueous solution of basic fuchsin or pararosaniline that is decolorized by sulfur dioxide, commonly prepared by addition of hydrochloric acid to a dye solution containing a metabisulphite or bisulphite salt; used for aldehydes and in histochemistry to detect polysaccharides, DNA, and proteins. See Feulgen stain, periodic acid-Schiff stain, ninhydrin-Schiff stain for proteins. Scott-Wilson r. an alkaline solution of mercuric cyanide and silver nitrate used in the detection of acetone. sulfhydryl r. r. that reacts with thiol groups, particularly those in proteins. Sulkowitch r. a r. for the detection of calcium in the urine, consisting of 2.5 g of oxalic acid, 2.5 g of ammonium oxalate, 5 mL of glacial acetic acid, and distilled water to make 150 mL; a milky precipitate of calcium oxalate is formed when the r. is added to urine that contains calcium. Uffelmann r. a solution prepared by adding a 2% solution of phenol in water to aqueous ferric chloride until the solution becomes violet in color; this turns lemon yellow in the presence of lactic acid, assumes an opaline tint in butyric acid, and is decolorized by hydrochloric acid. Wurster r. filter paper impregnated with tetramethyl-p-phenylenediamine, which turns blue in the presence of ozone or hydrogen peroxide.

reagin (re-a′jin)
1. Wolff-Eisner term for antibody. 2. Old term for the “Wassermann” antibody; not to be confused with the Prausnitz-Küstner antibody. 3. Antibodies that mediate immediate hypersensitivity reactions (IgE in humans). 4. SYN: homocytotropic antibody. atopic r. SYN: Prausnitz-Küstner antibody.

reaginic (re-a-jin′ik)
Pertaining to a reagin.

Abbreviation for Revised European-American Classification of Lymphoid Neoplasms. See R. classification .

reality (re-al′i-te)
That which exists objectively and in fact, and can be consensually validated. [L. res, thing, fact]

reality awareness
The ability to distinguish external objects as being different from oneself.

reamer (re′mer)
A rotating finishing or drilling tool used to shape or enlarge a hole in bone or a tooth. [A.S. ryman, to widen] engine r. an engine-mounted spirally bladed instrument, used for enlarging the root canals of teeth. intramedullary r. a rasp used for shaping the intramedullary canal of a large bone before inserting an appliance or prosthesis.

rearrangement (re-a-ranj-ment)
A restructuring; E.G., in a molecule. Amadori r. a r. that occurs in cross-linking reactions seen in collagen and in protein glycosylations; E.G., conversion of N-glycosides of aldoses to N-glycosides of the corresponding ketoses.


reattachment (re-a-tach′ment)
New epithelial or connective tissue attachment to the surface of a tooth that was surgically detached and not exposed to oral environment.

René A.F. de, French physicist, 1683–1757. See R. scale.

rebase (re′bas)
In dentistry, to refit a denture by replacing the denture base material without changing the occlusal relationship of the teeth. SEE ALSO: reline.

rebreathing (re-bredh′ing)
Inhalation of part or all of gases previously exhaled.

Rebuck skin window technique
See under technique.

An Escherichia coli protein that specifically recognizes single-stranded DNA and anneals it to a complementary sequence in a duplex that is homologous. This results in the displacement of the original complementary strand of the duplex.

recalcification (re-kal′si-fi-ka′shun)
Restoration to the tissues of lost calcium salts.

recall (re′kawl)
The process of remembering thoughts, words, and actions of a past event in an attempt to recapture actual happenings.

Joseph C.A., French gynecologist, 1774–1852. See R. operation.

recanalization (re-kan′al-i-za′shun)
1. Restoration of a lumen in a blood vessel following thrombotic occlusion, by organization of the thrombus with formation of new channels. 2. Spontaneous restoration of the continuity of the lumen of any occluded duct or tube, as with postvasectomy r..

recapitulation (re′ka-pit′u-la′shun)
See r. theory.

receiver (re-se′ver)
In chemistry, a vessel attached to a condenser to receive the product of distillation. [L. receptor, fr. recipio, to receive]

receptaculum, pl .receptacula (re′sep-tak′u-lum, -la)
A receptacle. SYN: reservoir. [L. fr. re-cipio, pp. -ceptus, to receive, fr. capio, to take] r. chyli SYN: cisterna chyli. r. ganglii petrosi SYN: petrosal fossula. r. pecqueti SYN: cisterna chyli.

receptive (re-sep′-tv)
Sensitive or responsive to stimulus. r. field that part of the retina of which the photoreceptors (rods and cones) pertain to a single optic nerve fiber. The response of a neuron to stimulation of its r. field depends on the type of neuron and the part of the field that is illuminated; an “on-center” neuron is stimulated by light falling at the center of its r. field and inhibited by light falling at the periphery; an “off-center” neuron reacts in exactly the opposite fashion; that is, it is inhibited by light falling at the center of its r. field. In either case, the net response depends on a complex switching action in the retina. When an entire r. field is equally illuminated, the response of receptors at the center of the field predominates.

receptor (re-sep′tor, tor)
1. A structural protein molecule on the cell surface or within the cytoplasm that binds to a specific factor, such as a drug, hormone, antigen, or neurotransmitter. 2. C. Sherrington term for any one of the various sensory nerve endings in the skin, deep tissues, viscera, and special sense organs. [L. receiver, fr. recipio, to receive] adrenergic receptors reactive components of effector tissues, most of which are innervated by adrenergic postganglionic fibers of the sympathetic nervous system. Such receptors can be activated by norepinephrine and/or epinephrine and by various adrenergic drugs; r. activation results in a change in effector tissue function, such as contraction of arteriolar muscles or relaxation of bronchial muscles; adrenergic receptors are divided into α-receptors and β-receptors, on the basis of their response to various adrenergic activating and blocking agents. SYN: adrenoceptor, adrenoreceptors. α-adrenergic receptors adrenergic receptors in effector tissues capable of selective activation and blockade by drugs; conceptually derived from the ability of certain agents, such as phenoxybenzamine, to block only some adrenergic receptors and of other agents, such as methoxamine, to activate only the same adrenergic receptors. Such receptors are designated as α-receptors. Their activation results in physiologic responses such as increased peripheral vascular resistance, mydriasis, and contraction of pilomotor muscles. β-adrenergic receptors adrenergic receptors in effector tissues capable of selective activation and blockade by drugs; conceptually derived from the ability of certain agents, such as propranolol, to block only some adrenergic receptors and of other agents, such as isoproterenol, to activate only the same adrenergic receptors. Such receptors are designated as β-receptors. Their activation results in physiologic responses such as increases in cardiac rate and force of contraction (β1), and relaxation of bronchial and vascular smooth muscle (β2) contained in skeletal muscle. AMPA r. a type of glutamate r. that participates in excitatory neurotransmission and also binds α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid and acts as a cation channel. SYN: quisqualate r.. angiotensin r. cell-surface G-protein–coupled receptors that mediate the effects of angiotensin II. Two types are recognized: AT1 and AT2; the former mediates the powerful vascular smooth-muscle contraction responsible for the hypertensive response produced by angiotensin II; the latter is not sufficiently understood to be assigned any physiologic function. ANP receptors cell surface receptors for atrial natriuretic peptide that have a single transmembrane spanning element; these have integral kinase and guanylate cyclase domains. ANP clearance receptors cell surface proteins that bind atrial natriuretic peptide and ANP fragments without initiating biologic action. asialoglycoprotein r. a surface r. found in hepatocytes that binds galactose-terminal glycoproteins; thus, this r. removes those proteins from circulation and they are in turn acted upon by hepatocyte lysosomes. B cell receptors a complex comprising a membrane-bound immunoglobulin molecule and two associated signal-transducing α and β chains. cholinergic receptors chemical sites in effector cells or at synapses through which acetylcholine exerts its action. epidermal growth factor r. (EGFR) r. often upregulated in epithelial tumors. estrogen r. r. for estrogens; its presence conveys a better prognosis for breast cancers. Fas r. See Fas. Fc r. receptors present on a variety of cells for the Fc fragment of immunoglobulins. These receptors recognize immunoglobulins of the IgG and IgE class. kainate r. a type of glutamate r. that participates in excitatory neurotransmission and also binds kainate and acts as a cation channel; injection of kainate causes death of neurons but preserves glial cells and axons. laminin r. a r. found in many cell types that binds laminin and has a role in cell attachment and neurite outgrowth. L-AP4 r. a type of glutamate r. that also binds a particular synthetic agonist and acts as a cation channel. low-density lipoprotein receptors receptors on the surface of cells, especially liver cells, which bind to low-density lipoprotein and promote clearance of LDL from the plasma. mannose-6-phosphate receptors (MPR) receptors in Golgi apparatus to which newly synthesized proteins that are destined to enter lysosomes bind. metabotropic r. a type of r. that is linked to intracellular production of 1,2-diacylglycerol and inositol 1,4,5-trisphosphate. [metabolism + G. trope, turning, inclination, + -ic] muscarinic receptors membrane-bound proteins whose extracellular domain contains a recognition site for acetylcholine (ACh); combination of Ach with the r. initiates a physiologic change (slowing of heart rate, increased glandular secretory activity, and stimulation of smooth muscle contractions); changes are observed after treatment with the mushroom alkaloid muscarine. Muscarinic receptors are to be distinguished from nicotinic receptors. nicotinic receptors a class of cholinergic receptors on skeletal muscle cells that are linked to ion channels in the cell membrane. nicotinic cholinergic r. a class of receptors responsive to acetylcholine that also are activated by nicotine; ganglionic (including the adrenal medulla) and neuromuscular receptors. Two classes exist: nicotinic-neuronal and nicotinic-muscular. NMDA r. a type of glutamate r. that participates in excitatory neurotransmission and also binds N-methyl-d-aspartate; may be particularly involved in the cell damage observed in individuals with Huntington disease. opiate receptors regions of the brain that have the capacity to bind morphine; some, along the aqueduct of Sylvius and in the center median, are in areas related to pain, but others, as in the striatum, are not related. orphan r. a nuclear r. for which no ligand has yet been identified. progesterone r. intracellular r. for progesterone; often over-expressed in breast cancer. quisqualate r. SYN: AMPA r.. retinoic acid r. nuclear r. for retinoic acid. retinoid X r. r. for retinoic acids; has less affinity for retinoic acid than the retinoic acid receptors; function is not yet well understood. ryanodine r. r. associated with a calcium conductance channel in the sacroplasmic or endoplasmic reticulum of cells, which when bound to ryanodine, causes the channel to remain in a subconductive state, allowing slow continuing release of calcium ions from the sarcoplasmic reticulum into the cytoplasm. The channels are normally sensitive to calcium ions and not sensitive to inositol triphosphate. scavenger r. a r. on macrophages that binds preferentially to oxidized LDL, causing macrophages to internalize the LDL. sensory receptors peripheral endings of afferent neurons. stretch receptors receptors that are sensitive to elongation, especially those in Golgi tendon organs and muscle spindles, but also those found in visceral organs such as the stomach, small intestine, and urinary bladder; these receptors have the function of detecting elongation, and this distinguishes them from baroreceptors, which actually are activated by stretching of the wall of the blood vessel but whose function is to elicit central reflex mechanism reducing the arterial blood pressure. T cell antigen receptors receptors present on T cells that interact with both processed antigen and major histocompatibility antigens simultaneously; these are heterodimers, each consisting of either an α and β chain or a γ and δ chain.

receptosomes (re-sep′to-soms)
Vesicles that avoid lysosomes and deliver their contents to other intracellular sites.

recess (re′ses) [TA]
A small hollow or indentation. SYN: recessus [TA] . [L. recessus] anterior r. a circumscript deepening of the interpeduncular fossa in the direction of the mamillary bodies. SYN: recessus anterior [TA] . anterior r. of tympanic membrane [TA] a slitlike space on the tympanic wall between the anterior malleolar fold and the tympanic membrane. SYN: recessus anterior membranae tympanicae [TA] , Tröltsch pockets, Tröltsch recesses. azygoesophageal r. the region below the azygos vein arch in which the right lung intrudes into the mediastinum between the heart and vertebral column, bordered on the left by the esophagus. cecal r. SYN: retrocecal r.. cerebellopontine r. cerebellopontine angle. cochlear r. [TA] a small depression on the inner wall of the vestibule of the labyrinth at the portion of the pyramid of vestibule, between the two limbs into which the vestibular crest divides posteriorly; it is perforated by foramina giving passage to fibers that the cochlear branch of the vestibulocochlear nerve sends to the posterior extremity of the cochlear duct. SYN: recessus cochlearis [TA] , Reichert cochlear r.. costodiaphragmatic r. [TA] the cleftlike extension of the pleural cavity between the diaphragm and the rib cage; pleural effusions collect here when in the upright position, and since the lung only partially enters, this is the site of thoracocentesis. SYN: recessus costodiaphragmaticus [TA] , phrenicocostal sinus. costomediastinal r. [TA] the r. of the pleural cavity between the costal cartilages and the mediastinum. SYN: recessus costomediastinalis [TA] , costomediastinal sinus. duodenojejunal r. SYN: superior duodenal fossa. elliptical r. of bony labyrinth [TA] an oval depression in the roof and inner wall of the vestibule of the labyrinth, lodging the utriculus. SYN: recessus ellipticus labyrinthi ossei [TA] , recessus utricularis labyrinthi ossei&star, utricular r. of bony labyrinth&star, fovea elliptica, fovea hemielliptica. epitympanic r. [TA] the upper portion of the tympanic cavity above the tympanic membrane; it contains the head of the malleus and the body of the incus. SYN: recessus epitympanicus [TA] , attic, epitympanic space, epitympanum, Hyrtl epitympanic r., tympanic attic. hepatoenteric r. a peritoneal r. at the caudal end of the embryonic pneumatoenteric r.; it separates the developing liver and stomach. hepatorenal r. of subhepatic space [TA] the deep r. of the subhepatic space of the peritoneal cavity on the right side extending upward between the liver in front and the kidney and suprarenal behind; this is a gravity-dependent portion of the peritoneal cavity when in the supine position; fluids draining from the omental bursa drain here. SYN: recessus hepatorenalis recessus subhepatici [TA] , hepatorenal pouch, Morison pouch. Hyrtl epitympanic r. SYN: epitympanic r.. inferior duodenal r. SYN: inferior duodenal fossa. inferior ileocecal r. [TA] a deep fossa sometimes found between the ileocecal fold, the mesoappendix, and the cecum. SYN: recessus ileocecalis inferior [TA] . inferior omental r. SYN: inferior r. of omental bursa. inferior r. of omental bursa [TA] a r. of the omental bursa extending between anterior and posterior layers of the great omentum. SYN: recessus inferior omentalis [TA] , inferior omental r.. infundibular r. [TA] a funnel-shaped diverticulum leading from the anterior portion of the third ventricle down into the infundibulum of the hypophysis. SYN: aditus ad infundibulum [TA] , recessus infundibuli [TA] . intersigmoid r. [TA] a triangular peritoneal r. posterior and inferior to the sigmoid colon created by the attachment of the sigmoid mesocolon ascending across the left psoas, then turning sharply to descend into the pelvis; the left ureter descends the posterior wall of this r.. SYN: recessus intersigmoideus [TA] . Jacquemet r. a pouch of peritoneum between the gallbladder and the liver. lateral r. of fourth ventricle [TA] the narrow r. of the ventricle that extends laterally over, and down along the side of, the inferior cerebellar peduncle and the overlying cochlear nuclei; at its tip it opens by way of Luschka foramen into the interopeduncular cistern of the subarachnoid space. By way of this r., part of the choroid plexus of the fourth ventricle protrudes into the subarachnoid space. SYN: recessus lateralis ventriculi quarti [TA] . mesentericoparietal r. SYN: parajejunal fossa. optic r. See supraoptic r.. pancreaticoenteric r. a r. of the embryonic peritoneal cavity that develops into the adult omental bursa. paracolic recesses SYN: paracolic gutters, under gutter. paraduodenal r. [TA] an occasional r. in the peritoneum to the left of the terminal portion of the duodenum located posterior to a fold containing the inferior mesenteric vein. SYN: recessus paraduodenalis [TA] , fossa venosa, paraduodenal fossa. parotid r. SYN: parotid space. pharyngeal r. [TA] a slitlike depression in the lateral membranous (nonmuscular) pharyngeal wall extending posterior to the opening of the pharyngotympanic (auditory) tube. SYN: recessus pharyngeus [TA] , recessus infundibuliformis, Rosenmüller fossa, Rosenmüller r.. phrenicomediastinal r. [TA] the r. of the pleural cavity between the diaphragm and the mediastinum. SYN: recessus phrenicomediastinalis [TA] . pineal r. [TA] a diverticulum from the posterior part of the third ventricle extending back between the posterior commissure and the habenular commissure; sometimes extending into the stalk of the pineal. SYN: recessus pinealis [TA] . piriform r. piriform fossa. pleural recesses [TA] four recesses of the pleural cavity, one behind the sternum and costal cartilages (costomediastinal r.), one between the diaphragm and chest wall (costodiaphragmatic r.), one between the diaphragm and mediastinum (phrenicomediastinal r.), and one between the vertebral bodies and mediastinum (vertebromediastinal r.). SYN: recessus pleurales [TA] , pleural sinuses. pneumatoenteric r., pneumoenteric r. a r. of the embryonic celom between the right lung bud and the gut; it is normally largely obliterated before birth, leaving only the superior r. of the vestibule of the lesser peritoneal sac as a vestige. pontocerebellar r. SYN: cerebellopontine angle. posterior r. [TA] a deepening of the interpeduncular fossa toward the pons. SYN: recessus posterior [TA] . posterior r. of tympanic membrane [TA] a narrow pocket in the tympanic wall between the posterior malleolar fold and the tympanic membrane. SYN: recessus posterior membranae tympanicae [TA] , Tröltsch pockets, Tröltsch recesses. Reichert cochlear r. SYN: cochlear r.. retrocecal r. [TA] one of several small pockets sometimes found extending alongside the right margin of the ascending colon near the cecum. SYN: recessus retrocecalis [TA] , cecal r.. retroduodenal r. [TA] a peritoneal r. occasionally found behind the third part of the duodenum, between it and the aorta. SYN: recessus retroduodenalis [TA] , infraduodenal fossa, retroduodenal fossa. Rosenmüller r. SYN: pharyngeal r.. sacciform r. of distal radioulnar joint [TA] an extension of the cavity of the distal radioulnar articulation proximad between the two bones; SYN: recessus sacciformis articulationis radioulnaris distalis [TA] . sacciform r. of elbow joint [TA] an extension of the capsule of the elbow joint at the neck of the radius. SYN: recessus sacciformis articulationis [TA] . saccular r. of bony labyrinth spherical r. of bony labyrinth. sphenoethmoidal r. [TA] a small cleftlike pocket of the nasal cavity above the superior concha into which the sphenoid sinuses drain. SYN: recessus sphenoethmoidalis [TA] . spherical r. of bony labyrinth [TA] a rounded depression on the inner wall of the vestibule of the labyrinth, lodging the sacculus. SYN: recessus saccularis larbyrinthi ossei&star, saccular r. of bony labyrinth&star, fovea hemispherica, fovea spherica, recessus sphericus labyrinthi ossei. splenic r. [TA] the extension of the omental bursa toward the hilum of the spleen. SYN: recessus splenicus [TA] , recessus lienalis&star. subhepatic r. SYN: subhepatic space. subphrenic recesses SYN: subphrenic space. subpopliteal r. [TA] the extension of the cavity of the knee joint between the tendon of the popliteus and lateral condyle of the femur. SYN: recessus subpopliteus [TA] , bursa of popliteus. superior azygoesophageal r. the region above the azygos vein arch in which the right lung is in contact with the esophagus. superior duodenal r. superior duodenal fossa. superior ileocecal r. [TA] a shallow pouch occasionally existing between the terminal ileum, the cecum, and the ileocolic artery when the latter is present. SYN: recessus ileocecalis superior [TA] . superior r. of lesser peritoneal sac pneumatoenteric r.. superior omental r. SYN: superior r. of omental bursa. superior r. of omental bursa [TA] a portion of the vestibule of the bursa omentalis that extends upward between the inferior vena cava and the esophagus. SYN: recessus superior bursae omentalis [TA] , superior omental r.. superior r. of tympanic membrane [TA] a space in the mucous membrane on the inner surface of the tympanic membrane between the flaccid part of the membrane and the neck of the malleus. SYN: recessus superior membranae tympanicae [TA] , Prussak pouch, Prussak space. supraoptic r. a diverticulum extending forward from the anterior part of the third ventricle above the optic chiasm. SYN: recessus supraopticus [TA] , recessus supraopticus [TA] . suprapineal r. [TA] a variable diverticulum from the posterior portion of the third ventricle of the brain, running backward some distance above and beyond the pineal r.. SYN: recessus suprapinealis [TA] . supratonsillar r. SYN: supratonsillar fossa. triangular r. an occasional evagination of the anterior wall of the third ventricle of the brain between the anterior commissure and the diverging pillars of the fornix. SYN: recessus triangularis. Tröltsch recesses SYN: anterior r. of tympanic membrane, posterior r. of tympanic membrane. tubotympanic r. the dorsal portion of the embryonic first endodermal pharyngeal pouch; it develops into the middle ear cavity. recesses of tympanic cavity [TA] spaces of the tympanic wall around the tympanic membrane. SYN: recessus membranae tympanicae [TA] . utricular r. of bony labyrinth elliptical r. of bony labyrinth. utricular r. of membranous labyrinth [TA] part of the utricle that forms a blind-ended pouch that extends into the ellipsoid (utricular) r. of the bony labyrinth. SYN: recessus utricularis labyrinthi membranacei [TA] . vertebromediastinal r. [TA] pleural r. formed by the reflection of the mediastinal part of the parietal pleura onto the vertebral bodies. SYN: recessus vertebromediastinalis [TA] .

recession (re-sesh′un)
A withdrawal or retreating. SEE ALSO: retraction. [L. recessio (see recessus)] angle r. tearing of the iris root between the longitudinal and circular ciliary muscles; often leading to glaucoma. clitoral r. operative procedure to reduce the visual prominence of the clitoris that often occurs in females with congenital adrenal hyperplasia; distinct from clitoral amputation (clitorectomy) or clitoral reduction. SEE ALSO: clitoroplasty. gingival r. apical migration of the gingiva along the tooth surface, with exposure of the tooth surface. SYN: gingival atrophy, gingival resorption. tendon r. surgical displacement of the tendon of an eye muscle posterior to its anatomic insertion. SYN: curb tenotomy.

recessitivity (re′ses-i-tiv′i-te)
The state of being recessive (2).

recessive (re-ses′iv)
1. Drawing away; receding. 2. In genetics, denoting a trait due to a particular allele or alleles at a single locus that does not manifest itself unless mutant alleles are present on both homologous chromosomes of a pair.

recessus, pl .recessus (re-ses′sus) [TA]
SYN: recess. [L. a withdrawing, a receding] r. anterior [TA] SYN: anterior recess. r. anterior membranae tympanicae [TA] SYN: anterior recess of tympanic membrane. r. cochlearis [TA] SYN: cochlear recess. r. costodiaphragmaticus [TA] SYN: costodiaphragmatic recess. r. costomediastinalis [TA] SYN: costomediastinal recess. r. duodenalis inferior [TA] SYN: inferior duodenal fossa. r. duodenalis superior [TA] SYN: superior duodenal fossa. r. ellipticus labyrinthi ossei [TA] SYN: elliptical recess of bony labyrinth. r. epitympanicus [TA] SYN: epitympanic recess. r. hepatorenalis r. subhepatici [TA] SYN: hepatorenal recess of subhepatic space. r. ileocecalis inferior [TA] SYN: inferior ileocecal recess. r. ileocecalis superior [TA] SYN: superior ileocecal recess. r. inferior omentalis [TA] SYN: inferior recess of omental bursa. r. infundibuli [TA] SYN: infundibular recess. r. infundibuliformis SYN: pharyngeal recess. r. intersigmoideus [TA] SYN: intersigmoid recess. r. lateralis ventriculi quarti [TA] SYN: lateral recess of fourth ventricle. r. lienalis splenic recess. r. membranae tympanicae [TA] SYN: recesses of tympanic cavity, under recess. r. paraduodenalis [TA] SYN: paraduodenal recess. r. parotideus SYN: parotid space. r. pharyngeus [TA] SYN: pharyngeal recess. r. phrenicomediastinalis [TA] SYN: phrenicomediastinal recess. r. pinealis [TA] SYN: pineal recess. r. piriformis [TA] SYN: piriform fossa. r. pleurales [TA] SYN: pleural recesses, under recess. r. posterior [TA] SYN: posterior recess. r. posterior membranae tympanicae [TA] SYN: posterior recess of tympanic membrane. r. retrocecalis [TA] SYN: retrocecal recess. r. retroduodenalis [TA] SYN: retroduodenal recess. r. sacciformis articulationis [TA] SYN: sacciform recess of elbow joint. r. sacciformis articulationis radioulnaris distalis [TA] SYN: sacciform recess of distal radioulnar joint. r. saccularis larbyrinthi ossei spherical recess of bony labyrinth. r. sphenoethmoidalis [TA] SYN: sphenoethmoidal recess. r. sphericus labyrinthi ossei SYN: spherical recess of bony labyrinth. r. splenicus [TA] SYN: splenic recess. r. subhepaticus [TA] SYN: subhepatic space. r. subphrenicus [TA] SYN: subphrenic space. r. subpopliteus [TA] SYN: subpopliteal recess. r. superior bursae omentalis [TA] SYN: superior recess of omental bursa. r. superior membranae tympanicae [TA] SYN: superior recess of tympanic membrane. r. supraopticus [TA] SYN: supraoptic recess. r. supraopticus [TA] SYN: supraoptic recess. r. suprapinealis [TA] SYN: suprapineal recess. r. triangularis SYN: triangular recess. r. utricularis labyrinthi membranacei [TA] SYN: utricular recess of membranous labyrinth. r. utricularis labyrinthi ossei elliptical recess of bony labyrinth. r. vertebromediastinalis [TA] SYN: vertebromediastinal recess.

recidivation (re-sid-i-va′shun)
Relapse of a disease, a symptom, or a behavioral pattern such as an illegal activity for which one was previously imprisoned. [L. recidivus, falling back, recurring, fr. re- cido, to fall back]

recidivism (re-sid′i-vizm)
The tendency of an individual toward recidivation. [L. recidivus, recurring]

recidivist (re-sid′i-vist)
A person who tends toward recidivation.

recipe (℞) (res′i-pe)
1. The superscription of a prescription, usually indicated by the sign ℞. 2. A prescription or formula. [L. imperative recipio, to receive]

recipient (re-sip′e-ent)
One who receives, as in blood transfusion or tissue or organ transplant. [L. recipiens, fr. recipio, to receive]

recipiomotor (re-sip′e-o-mo′ter)
Relating to the reception of motor stimuli. [L. recipio, to receive, + motor, mover]

reciprocation (re-sip-ro-ka′shun)
In prosthodontics, the means by which one part of an appliance is made to counter the effect created by another part. [L. reciprocare, pp. reciprocatus, to move back and forth]


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