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Medical Dictionary


prefrontal (pre-fron′tal)
1. Denoting the anterior portion of the frontal lobe of the cerebrum. 2. Denoting the granular frontal cortex rostral to the premotor area.

preganglionic (pre′gang-gle-on′ik)
Situated proximal to or preceding a ganglion; referring specifically to the p. motor neurons of the autonomic nervous system (located in the spinal cord and brainstem) and the p., myelinated nerve fibers by which they are connected to the autonomic ganglia.

pregnancy (preg′nan-se)
The state of a female after conception and until the termination of the gestation. SYN: fetation, gestation, gravidism, graviditas. [L. praegnans (praegnant-), pregnant, fr. prae, before, + gnascor, pp. natus, to be born] abdominal p. the implantation and development of the ovum in the peritoneal cavity, usually secondary to an early rupture of a tubal p.; very rarely, primary implantation may occur in the peritoneal cavity. SYN: abdominocyesis (1) , intraperitoneal p.. aborted ectopic p. SYN: tubal abortion. ampullar p. tubal p. situated near the midportion of the oviduct. cervical p. the implantation and development of the impregnated ovum in the cervical canal. chemical p. slight, unsustained rise in HCG levels. combined p. coexisting uterine and ectopic p.. compound p. development of a uterine p. in addition to a previously existing ectopic p. (usually a lithopedion). cornual p. the implantation and development of the impregnated ovum in one of the cornua of the uterus. ectopic p. the development of an impregnated ovum outside the cavity of the uterus. SYN: eccyesis, extrauterine p., heterotopic p., paracyesis. extraamniotic p. a p. in which the chorion is intact, but the amnion has ruptured and shrunk. SYN: graviditas examnialis. extrachorial p. p. in which the membranes rupture and shrink, causing the fetus to develop outside the chorionic sac but within the uterus. SYN: graviditas exochorialis. extramembranous p. a p. in which during the course of gestation the fetus has broken through its envelopes, coming directly in contact with the uterine walls. extrauterine p. SYN: ectopic p.. fallopian p. SYN: tubal p.. false p. a condition in which some signs and symptoms suggest p., although the woman is not pregnant. SYN: hysterical p., pseudocyesis, pseudopregnancy (1) , spurious p.. heterotopic p. SYN: ectopic p.. heterotropic pregnancies pregnancies occurring simultaneously in different sites, e.g., intrauterine and ampullary. higher order p. a p. that has three fetuses (triplets) or more. hydatid p. the presence of a hydiform mole in the pregnant uterus. hysterical p. SYN: false p.. interstitial p. SYN: intramural p.. intraligamentary p. p. within the broad ligament. intramural p. development of the fertilized ovum in the uterine portion of the fallopian tube. SYN: interstitial p., tubouterine p.. intraperitoneal p. SYN: abdominal p.. molar p. p. marked by a neoplasm within the uterus, whereby part or all of the chorionic villi are converted into a mass of clear vesicles. multiple p. condition of bearing two or more fetuses simultaneously. SYN: polycyesis. mural p. p. in uterine muscular wall. ovarian p. development of an impregnated ovum in an ovarian follicle. SEE ALSO: Spiegelberg criteria, under criterion. SYN: oocyesis, ovariocyesis. ovarioabdominal p. ovarian p. that, as the result of the embryo's growth, becomes abdominal. persistent ectopic p. an ectopic p. that has persistent viable tissue, secreting hCG after conservative surgery. postdate p. a p. of more than 294 days or 42 completed weeks. SYN: prolonged p.. prolonged p. SYN: postdate p.. secondary abdominal p. a condition in which the embryo or fetus continues to grow in the abdominal cavity after its expulsion from the fallopian tube or other seat of its primary development. SYN: abdominocyesis (2) . spurious p. SYN: false p.. tubal p. development of an impregnated ovum in the fallopian tube. SYN: fallopian p., salpingocyesis. tuboabdominal p. development of an ectopic p. partly in the fallopian tube and partly in the abdominal cavity. tuboovarian p. development of the ovum at the fimbriated extremity of the fallopian and involving the ovary. tubouterine p. SYN: intramural p.. twin p. a p. that may result from the fertilization of two separate ova or of a single ovum. SEE ALSO: twin. uterine p. development of fetus within the uterus. uteroabdominal p. development of the ovum primarily in the uterus and later, in consequence of the rupture of the uterus, in the abdominal cavity.

pregnane (preg′nan)
Parent hydrocarbon of two series of steroids stemming from 5α-p. (originally allopregnane) and 5β-p. (17β-ethyletiocholane). 5β-P. is the parent of the progesterones, p. alcohols, ketones, and several adrenocortical hormones and is found largely in urine as a metabolic product of 5β-p. compounds. For structure, see steroids.

pregnanediol (preg-nan-di′ol)
5β-Pregnane-3α,20α-diol;the chief steroid metabolite of progesterone that is biologically inactive and occurs as p. glucuronate in the urine.

pregnanedione (preg-nan-di′on)
5β-Pregnane-3,20-dione;a metabolite of progesterone, formed in relatively small quantities, that occurs in 5α and 5β isomeric forms.

pregnanetriol (preg-nan-tri′ol)
5β-Pregnane-3α,17α,20α-triol;a urinary metabolite of 17-hydroxyprogesterone and a precursor in the biosynthesis of cortisol; its excretion is enhanced in certain diseases of the adrenal cortex and following administration of corticotropin.

Denoting a gestating female. SYN: gravid. [see pregnancy]

pregnene (preg′nen)
An unsaturated steroid of primarily terminologic importance; utilized in systematic nomenclature of appropriate 21-carbon steroids.

pregneninolone (preg-nen-in′o-lon, preg-nen′in-)
SYN: ethisterone.

pregnenolone (preg-nen′o-lon)
3β-Hydroxy-5-pregnen-20-one;a steroid that serves as an intermediate in the biosynthesis of numerous hormones, including progesterone. p. succinate a corticosteroid used for the treatment of rheumatoid arthritis.

prehallux (pre-hal′uks)
A supernumerary digit, usually only partial, attached to the medial border of the great toe. [pre- + Mod. L. hallux, great toe]

prehelicine (pre-hel′i-sen)
In front of the helix of the pinna.

prehemataminic acid (pre′hem-ta-min′ik)
SYN: neuraminic acid.

prehensile (pre-hen′sil)
Adapted for taking hold of or grasping. [L. prehendo, pp. -hensus, to lay hold of, seize]

prehension (pre-hen′shun)
The act of grasping, or taking hold of.

prehormone (pre-hor′mon)
A glandular secretory product, having little or no inherent biologic potency, that is converted peripherally to an active hormone. Cf.:prohormone (1) .

prehyoid (pre-hi′oyd)
Anterior or superior to the hyoid bone; denoting certain accessory thyroid glands lying superior to the mylohyoid muscle.

preictal (pre-ik′tal)
Occurring before a seizure or stroke. [pre- + L. ictus, a stroke]

preinduction (pre-in-duk′shun)
An effect from the action of environment on the germ cells of progenitors upon their grandchildren. [L. prae, before, + inductio, a bringing in, fr. induco, to lead in]

Hugo von, Hungarian bacteriologist, 1860–1940.

prekallikrein (pre-kal-i-kre′in)
A plasma glycoprotein that in complex with kininogen serves as a cofactor in the activation of factor XII. P. also serves as the proenzyme for plasma kallikrein. SYN: Fletcher factor.

prelacrimal (pre-lak′ri-mal)
Anterior to the lacrimal sac.

prelaryngeal (pre-la-rin′je-al)
Anterior to the larynx; denoting especially one or two small lymphatic nodes.

preleptotene (pre-lep′to-ten)
The earliest stage of prophase in meiosis, characterized by physiochemical changes in cytoplasm and karyoplasm and beginning contraction of chromosomes. [pre- + leptotene, fr. G. leptos, slender, + tainia, band]

preleukemia (pre-loo-ke′me-a)
A syndrome that in time may develop into overt leukemia. It is characterized by bone marrow dysfunction manifested by anemia, neutropenia, and thrombocytopenia. SYN: myelodysplastic syndrome.

prelimbic (pre-lim′bik)
Anterior to the limbus of the fossa ovalis.

preload (pre′lod)
1. The load to which a muscle is subjected before shortening. 2. SYN: ventricular p.. ventricular p. formerly, the end-diastolic pressure stretching the ventricular walls, which determines the end-diastolic fiber length at the onset of ventricular contraction, or some other measure of this load on the muscle fibers before contraction; now, more rigorously expressed in terms of the wall stress at this moment, related to the tension per unit cross-sectional area in the ventricular muscle fibers (calculated by Laplace law from internal radius and pressure modified by wall thickness) that balances this transmural pressure at the moment before contraction begins. SYN: p. (2) .

premalignant (pre-ma-lig′nant)
SYN: precancerous.

premaniacal (pre-ma-ni′a-kal)
Preceding a manic attack.

premature (pre-ma-toor′, -choor)
1. Occurring before the usual or expected time. 2. Denoting an infant born at a gestational age of less than 37 weeks; birth weight is no longer considered a critical criterion for use of this designation. [L. praematurus, too early, fr. prae-, pre- + maturus, ripe (mature)]

prematurity (pre-ma-toor′i-te, -choor′i-te)
1. The state of being premature. 2. In dentistry, deflective occlusal contact.

premaxilla (pre-mak-sil′a)
1. incisive bone. 2. The central isolated bony part in a complete bilateral cleft of the lip. [pre- + L. maxilla, jawbone]

premaxillary (pre-mak′si-lar-e)
1. Anterior to the maxilla. 2. Denoting the premaxilla.

premedication (pre′med-i-ka′shun)
1. Administration of drugs prior to anesthesia to allay apprehension, produce sedation, and facilitate the administration of anesthesia. 2. Drugs used for such purposes.

premelanosome (pre-mel′a-no-som)
A nonpigmented membrane-bound vesicle in a melanocyte that contains tyrosine and matures into the melanin-filled melanosome; prominent in melanocytes of albinos.

premenstrual (pre-men′stroo-al)
Relating to the period of time preceding menstruation.

premenstruum (pre-men′stroo-um)
The few days preceding menstruation. [pre- + L. menstruum, ntr. of menstruus, monthly, pertaining to menstruation]

premitochondria (pre-mi-to-kon′dre-a)
SYN: promitochondria.

premolar (pre-mo′lar)
1. Anterior to a molar tooth. 2. A bicuspid tooth.

premonocyte (pre-mon′o-sit)
An immature monocyte not normally seen in the circulating blood. SYN: promonocyte.

premorbid (pre-mor′bid)
Preceding the occurrence of disease. [pre- + L. morbidus, ill, fr. morbus, disease]

premunition (pre-moo-nish′un)
A state of existing resistance of a host to infection or reinfection with a parasite; used especially in malaria epidemiology. [L. praemunitio, fortification in advance, fr. prae-, + munio, to fortify]

premunitive (pre-moo′ni-tiv)
Relating to premunition.

premyeloblast (pre-mi′e-lo-blast)
The earliest recognizable precursor of the myeloblast.

premyelocyte (pre-mi′e-lo-sit)
SYN: promyelocyte.

prenaris, pl .prenares (pre-na′ris, na′rez)
SYN: naris.

prenatal (pre-na′tal)
Preceding birth. SYN: antenatal. [pre- + L. natus, born]

preneoplastic (pre′ne-o-plas′tik)
Preceding the formation of any neoplasm, benign or malignant; a p. condition is not always precancerous, although the term is frequently used erroneously in that sense. [pre- + G. neos, new, + plastikos, formative]

Charles F., U.S. optician, 1854–1946. See P. rule.

prenyl (pren′il)
Poly- or multiprenyl residues or derivatives thereof, apparently formed by end-to-end polymerization of isoprene molecules; found in the isoprenoids in nature.

prenylamine (pre-nil′a-men)
An antianginal agent.

prenylation (pren′il-a′shun)
The covalent addition of prenyl and multiprenyl residues to a macromolecule.

preoperative (pre-op′er-a-tiv)
Preceding an operation.

preoptic (pre-op′tik)
Referring to the p. region.

preoral (pre-o′ral)
In front of the mouth. [pre- + L. os (or-), mouth]

preosteoblast (pre-os′te-o-blast)
SYN: osteoprogenitor cell.

preoxygenation (pre′ok-se-je-na′shun)
Denitrogenation with 100% oxygen prior to induction of general anesthesia.

prep (prep)
To prepare the skin or other body surface for an operative procedure, usually by cleaning and application of antiseptic solutions. [slang for preparation or prepare]

prepalatal (pre-pal′a-tal)
Relating to the anterior part of the palate, or anterior to the palate bone.

preparation (prep-a-ra′shun)
1. A getting ready. 2. Something made ready, as a medicinal or other mixture, or a histologic specimen. [L. praeparatio, fr. prae, before, + paro, pp. -atus, to get ready] cavity p. 1. removal of dental caries and surgical p. of the remaining tooth structure to receive a dental restoration; 2. the final form of an excavation in a tooth resulting from such p.. corrosion p. a p. in which the hollow parts such as ducts, vessels, or alveoli of the lung are filled with a substance that hardens and persists after dissolving the tissues by digestion. cytologic filter p. a cytologic specimen made by depositing a watery sample (obtained by a variety of methods from many body sites) upon a filter having pores of uniform size smaller than the cellular material to be concentrated; this is followed by fixation and staining, usually with 95% ethyl alcohol and Papanicolaou stain. heart-lung p. an animal p. in which blood (rendered incoagulable) circulates through the heart and lungs and through an artificial system of vessels representing the systemic circulation; the latter is connected with the divided aorta on the one hand and with the superior vena cava on the other; used in physiologic studies of the heart and circulation.

preparturient (pre-par-too′re-ent)
Relating to the period before birth.

prepatellar (pre-pa-tel′ar)
Anterior to the patella.

preperitoneal (pre′per-i-to-ne′al)
Denoting a fatty layer between the peritoneum and the transversalis fascia in the lower anterior abdominal wall.

prephenic acid (pre-fe′nik, -fen′ik)
An intermediate in the microbial conversion of shikimic acid to l-phenylalanine and l-tyrosine.

preplacental (pre-pla-sen′tal)
Before formation of a placenta.

preponderance (pre-pon′der-ans)
Quality of outweighing, or exceeding in extent or importance. directional p. a right or left predominance of nystagmus calculated from the responses to the binaural, bithermal caloric test.

prepotential (pre-po-ten′shal)
A gradual rise in potential between action potentials as a phasic swing in electric activity of the cell membrane, which establishes its rate of automatic activity, as in the ureter or cardiac pacemaker.

preprocollagen (pre-pro-kol-o-jen)
The precursor of collagen that is synthesized on ribosomes; procollagen with a leader or signal sequence that directs the polypeptide chain into the vesicular space of the endoplasmic reticulum.

preproinsulin (pre-pro-in′soo-lin)
The precursor protein to proinsulin. See preprotein.

preproprotein (pre-pro-pro′ten)
A precursor to an inactive secretory proprotein.

preprotein (pre-pro′ten)
A secretory protein with a signal peptide region attached.

prepsychotic (pre-si-kot′ik)
1. Relating to the period antedating the onset of psychosis. 2. Denoting a potential for a psychotic episode, one that appears imminent under continued stress.

prepuberal, prepubertal (pre-pu′ber-al, -ber-tal)
Before puberty.

prepubescent (pre-pu-bes′ent)
Immediately prior to the commencement of puberty.

prepuce (pre′poos) [TA]
A free fold of skin that covers. SYN: preputium [TA] , foreskin&star. [L. praeputium, foreskin] p. of clitoris [TA] the external fold of the labia minora, forming a cap over the clitoris. SYN: preputium clitoridis. hooded p. incomplete circumferential formation of foreskin with a dorsal component (the dorsal hood) but an absent or incomplete ventral portion. Typically seen in boys with hypospadias or isolated chordee. In the rare condition of epispadias, the incomplete portion may be ventral. p. of penis [TA] the free fold of skin that covers, more or less completely, the glans penis. SYN: foreskin of penis [TA] , preputium penis [TA] . ventral apron p. the incomplete foreskin seen in epispadias patients typically such that a ventral apron remains.

preputial (pre-pu′she-al)
Relating to the prepuce.

preputiotomy (pre-pu′she-ot′o-me)
Incision of prepuce. [preputium + G. tome, incision]

preputium, pl .preputia (pre-pu′she-um, she-a) [TA]
SYN: prepuce. [L. praeputium] p. clitoridis SYN: prepuce of clitoris. p. penis [TA] SYN: prepuce of penis.

prepyloric (pre-pi-lor′ik)
Anterior to or preceding the pylorus; denoting a temporary constriction of the wall of the stomach separating the fundus from the antrum during digestion.

prerectal (pre-rek′tal)
Anterior to or preceding the rectum.

prereduced (pre-re-doosd′)
Pertaining to bacteriologic media that are boiled, tubed under oxygen-free gas with chemical reducing agents and colorimetric redox indicator in stoppered tubes or bottles, and then sterilized.

prerenal (pre-re′nal)
Anterior to a kidney. [L. ren, kidney]

preretinal (pre-ret′i-nal)
Anterior to the retina.

presacral (pre-sa′kral)
Anterior to or preceding the sacrum.

presby-, presbyo-
Old age. SEE ALSO: gero-. [G. presbys, old man]

presbyacousia (prez-be-a-koo′se-a)
SYN: presbyacusis.

presbyacusis, presbyacusia (prez′be-a-koo′sis)
Loss of ability to perceive or discriminate sounds associated with aging; the pattern and age of onset vary. SYN: presbyacousia, presbycusis. [presby- + G. akousis, hearing]

presbyastasis (prez′bi-a-sta′sis)
Impairment of vestibular function associated with aging. [ presby- + G. a- priv. + stasis, standing]

presbyatrics (prez-be-at′riks)
Rarely used terms for geriatrics. [presby- + G. iatreia, medical treatment]

presbycusis (prez-be-koo′sis)
SYN: presbyacusis.

presbyopia (Pr) (prez-be-o′pe-a)
The physiologic loss of accommodation in the eyes in advancing age, said to begin when the near point has receded beyond 22 cm (9 inches). [presby- + G. ops, eye]

presbyopic (prez′be-op′ik, -o′pik)
Relating to or suffering from presbyopia.

prescribe (pre-skrib)
To give directions, either orally or in writing, for the preparation and administration of a remedy to be used in the treatment of any disease. [L. prae-scribo, pp. -scriptus, to write before]

prescription (pre-skrip′shun)
1. A written formula for the preparation and administration of any remedy. 2. A medicinal preparation compounded according to formulated directions, said to consist of four parts: 1) superscription, consisting of the word recipe, take, or its sign, ℞; 2) inscription, the main part of the p., containing the names and amounts of the drugs ordered; 3) subscription, directions for mixing the ingredients and designation of the form (pill, powder, solution, etc.) in which the drug is to be made, usually beginning with the word, misce, mix, or its abbreviation, M.; 4) signature, directions to the patient regarding the dose and times of taking the remedy, preceded by the word signa, designate, or its abbreviation, S. or Sig. [L. praescriptio; see prescribe] shotgun p. a p. containing many ingredients, some of which may be useless, in an attempt to cover all possible types of therapy that may be needed; a pejorative term.

presenile (pre-se′nil)
Prior to the usual onset of senility, as in the milder, p. dementia.

presenility (pre-se-nil′i-te)
Premature old age; the condition of an individual, not old in years, who displays the physical and mental characteristics of old age but not to the extent of senility. [pre- + L. senilis, old]

presenium (pre-se′ne-um)
The period preceding old age.

present (pre-zent′)
1. To precede or appear first at the os uteri, said of the part of the fetus first felt during examination. 2. To appear for examination, treatment, etc., said of a patient. [L. praesens (-sent-), pres. p. of prae-sum, to be before, be at hand]

presentation (pre′zen-ta′shun, prez′)
That part of the fetus presenting at the superior strait of the maternal pelvis; occiput, chin, and sacrum are, respectively, the determining points in vertex, face, and breech p.. SEE ALSO: position (3) .position. [see present] acromion p. SYN: shoulder p.. breech p. p. of any part of the pelvic extremity of the fetus, the nates, knees, or feet; more properly only of the nates; frank breech p. occurs when the fetus presents by the pelvic extremity; the thighs may be flexed and the legs extended over the anterior surfaces of the body; in full breech p., the thighs may be flexed on the abdomen and the legs upon the thighs; and in footling p., foot p., the feet may be the lowest part; in incomplete foot p., incomplete knee p., one leg may retain the position that is typical of one of the above-mentioned presentations, while the other foot or knee may present. SYN: pelvic p.. brow p. cephalic p.. cephalic p. p. of any part of the fetal head, usually the upper and back part, as a result of flexion such that the chin is in contact with the thorax in vertex p.; there may be degrees of flexion so that the presenting part is the large fontanel in sincipital p., the brow in brow p., or the face in face p.. SYN: head p.. compound p. prolapse of an extremity, usually a hand, along the presenting part, with both in the pelvis simultaneously. face p. cephalic p.. footling p. breech p.. frank breech p. See breech p.. head p. SYN: cephalic p.. incomplete foot p. breech p.. knee p. breech p.. pelvic p. SYN: breech p.. placental p. SYN: placenta previa. polar p. the p. of either pole of the fetal oval; may be either a cephalic or breech p., or a longitudinal lie. shoulder p. transverse p. with the shoulder as the presenting part. SYN: acromion p.. sincipital p. cephalic p.. transverse p. an abnormal p., neither head nor breech, in which the fetus lies transversely in the uterus across the axis of the parturient canal. vertex p. cephalic p..

preservative (pre-zer′va-tiv)
A substance added to food products or to an organic solution to prevent chemical change or bacterial action.

presomite (pre-so′mit)
Relating to the embryonic stage before the appearance of somites (before day 19 in the human).

presphenoid (pre-sfe′noyd)
In front of the sphenoid bone or cartilage.

presphygmic (pre-sfig′mik)
Preceding the pulse beat; denoting a brief interval following the filling of the ventricles with blood before their contraction forces open the semilunar valves, corresponding to the isovolumic contraction period. [pre- + G. sphygmos, pulse]

prespinal (pre-spi′nal)
Anterior to the spine.

prespondylolisthesis (pre-spon-di-lo-lis′the-sis)
A condition predisposing to spondylolisthesis, consisting of a defect in the laminae of a lumbar vertebra but before development of any displacement of the vertebral body. See spondylolysis.

pressor (pres′er, -or)
Exciting to vasomotor activity; producing increased blood pressure; denoting afferent nerve fibers that, when stimulated, excite vasoconstrictors, which increase peripheral resistance. SYN: hypertensor. [L. premo, pp. pressus, to press]

pressoreceptive (pres′o-re-sep′tiv)
Capable of receiving as stimuli changes in pressure, especially changes of blood pressure. SYN: pressosensitive.

pressoreceptor (pres′o-re-sep′ter, -tor)
SYN: baroreceptor.

pressosensitive (pres-o-sen′si-tiv)
SYN: pressoreceptive.


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