| orifice of external acoustic meatus | The orifice of the external acoustic meatus in the tympanic portion of the temporal bone. Synonym: porus acusticus externus, external acoustic foramen, external acoustic pore, external auditory pore, external auditory foramen, orifice of external acoustic meatus. (05 Mar 2000) |
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| orifice of inferior vena cava | The orifice through which the inferior vena cava opens into the right atrium. Synonym: ostium venae cavae inferioris, orifice of inferior vena cava. (05 Mar 2000) |
| orifice of internal acoustic meatus | The inner opening of the internal acoustic meatus on the posterior surface of the petrous part of the temporal bone. Synonym: porus acusticus internus, internal acoustic foramen, internal acoustic pore, auditory pore, internal auditory foramen, orifice of internal acoustic meatus. (05 Mar 2000) |
| orifice of superior vena cava | The point of entry of the superior vena cava into the right atrium. Synonym: ostium venae cavae superioris, orifice of superior vena cava. (05 Mar 2000) |
| orificial | Relating to an orifice of any kind. (05 Mar 2000) |
| orificium | Synonym: orifice, orifice. Origin: L. (05 Mar 2000) |
| orificium externum uteri | The vaginal opening of the uterus. Synonym: ostium uteri, mouth of the womb, opening of uterus, orificium externum uteri, os uteri externum, ostium uteri externum. (05 Mar 2000) |
| orificium internum uteri | An elongated constriction at the junction of the body and cervix of the uterus. Synonym: isthmus uteri, Guyon's isthmus, orificium internum uteri, os uteri internum, ostium uteri internum. (05 Mar 2000) |
| orificium ureteris | The opening of the ureter in the bladder, situated one at each lateral angle of the trigone; wide gaping of the ostium usually indicates vesicoureteral reflux. Synonym: ostium ureteris, orificium ureteris, ureteral meatus, ureteral opening. (05 Mar 2000) |
| orificium urethrae externum | The slitlike opening of the urethra in the glans penis, the external orifice of the urethra (in the female) in the vestibule, usually upon a slight elevation, the papilla urethrae. Synonym: ostium urethrae externum, external opening of urethra, meatus urinarius, orificium urethrae externum. (05 Mar 2000) |
| orificium vaginae | The narrowest portion of the canal, in the floor of the vestibule posterior to the urethral orifice. Synonym: ostium vaginae, orificium vaginae, vaginal opening. (05 Mar 2000) |
| origanum | <botany> A genus of aromatic labiate plants, including the sweet marjoram (O. Marjorana) and the wild marjoram (O. Vulgare). Origin: L. Origanum, Gr, prob. Fr. Mountain + brightness, beauty. Cf. Organy. Source: Websters Dictionary (01 Mar 1998) |
| origanum oil | The volatile oil (which contains carvacrol) obtained from various species of Origanum (family Labiatae); used as a rubefacient, as a constituent in veterinary liniments, and in microscopic techniques. (05 Mar 2000) |
| origin | 1. The first existence or beginning of anything; the birth. "This mixed system of opinion and sentiment had its origin in the ancient chivalry." (Burke) 2. That from which anything primarily proceeds; the fountain; the spring; the cause; the occasion. 3. <anatomy> The point of attachment or end of a muscle which is fixed during contraction; in contradistinction to insertion. <mathematics> Origin of coordinate axes, the point where the axes intersect. See Note under Ordinate. Synonym: Commencement, rise, source, spring, fountain, derivation, cause, root, foundation. Origin, Source. Origin denotes the rise or commencement of a thing; source presents itself under the image of a fountain flowing forth in a continuous stream of influences. The origin of moral evil has been much disputed, but no one can doubt that it is the source of most of the calamities of our race. "I think he would have set out just as he did, with the origin of ideas the proper starting point of a grammarian, who is to treat of their signs." (Tooke) "Famous Greece, That source of art and cultivated thought Which they to Rome, and Romans hither, brought." (Waller) Origin: F. Origine, L. Origo, -iginis, fr. Oriri to rise, become visible; akin to Gr. To stir up, rouse, Skr. R, and perh. To E. Run. Source: Websters Dictionary (01 Mar 1998) |
| origin of replication | <molecular biology> Regions of DNA that are necessary for its replication to begin, such as pBR322 ori, required for plasmid replication. (18 Nov 1997) |