| incisive foramen | One of several (usually four) openings of the incisive canals into the incisive fossa. Synonym: foramen incisivum, incisor foramen, Stensen's foramen. (05 Mar 2000) |
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| incisor foramen | One of several (usually four) openings of the incisive canals into the incisive fossa. Synonym: foramen incisivum, incisor foramen, Stensen's foramen. (05 Mar 2000) |
| inferior dental foramen | The opening into the mandibular canal on the medial surface of the ramus of the mandible giving passage to the inferior alveolar nerve, artery, and vein. Synonym: foramen mandibulae, inferior dental foramen. (05 Mar 2000) |
| infraorbital foramen | The external opening of the infraorbital canal, on the anterior surface of the body of the maxilla. Synonym: foramen infraorbitale. (05 Mar 2000) |
| interatrial foramen primum | In the embryonic heart, the temporary opening between right and left atria situated between the lower margin of the septum primum and the atrioventricular canal cushions, in an adult heart, the abnormal persistence of the so-named communication which is normal in young embryos. Synonym: foramen subseptale, ostium primum, primary interatrial foramen. (05 Mar 2000) |
| interatrial foramen secundum | A secondary opening appearing in the upper part of the septum primum in the sixth week of embryonic life, just prior to the closure of the interatrial foramen primum. Synonym: ostium secundum, secondary interatrial foramen. (05 Mar 2000) |
| internal acoustic foramen | 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) |
| internal auditory foramen | 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) |
| interventricular foramen | The short, often slitlike passage that, on both the left and right side, connects the third brain ventricle (of the diencephalon) with the lateral ventricles (of the cerebral hemispheres); the passage is bounded anteriomedially by the column of fornix and posterolaterally by the anterior pole of the thalamus. Synonym: foramen interventriculare, Monro's foramen, porta. (05 Mar 2000) |
| intervertebral foramen | One of a number of openings into the vertebral canal bounded by the pedicles of adjacent vertebrae above and below, the vertebral body (mostly of the superior vertebra) and intervertebral disc anteriorly, and the articular processes forming the zygopophyseal joint posteriorly. Synonym: foramen intervertebrale. (05 Mar 2000) |
| obturator foramen | A large, oval or irregularly triangular aperture in the hip bone, the margins of which are formed by the pubis and the ischium; it is closed in the natural state by the obturator membrane, except for a small opening for the passage of the obturator vessels and nerve. Synonym: foramen obturatum. (05 Mar 2000) |
| olfactory foramen | One of the openings in the cribriform plate of the ethmoid bone, transmitting the olfactory nerves. (05 Mar 2000) |
| optic foramen | The short canal through the lesser wing of the sphenoid bone at the apex of the orbit that gives passage to the optic nerve and the ophthalmic artery. Synonym: canalis opticus, foramen opticum, optic foramen. (05 Mar 2000) |
| thyroid foramen | An opening occasionally existing in one or both of the plates of the thyroid cartilage. Synonym: foramen thyroideum. (05 Mar 2000) |
| emissary sphenoidal foramen | <anatomy> A minute inconstant foramen in the greater wing of the sphenoid bone, anterior and medial to the foramen ovale, transmitting a small emissary vein from the cavernous sinus. Synonym: emissary sphenoidal foramen, venous foramen, Vesalius' foramen. (05 Mar 2000) |