| inferior nasal arteriole of retina | The branch of the central artery of the retina that supplies the lower medial, or nasal, part of the retina. Synonym: arteriola nasalis retinae inferior. (05 Mar 2000) |
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| inferior nasal colliculus | The ovoid, paired, inferior eminence of the laminae of mesencephalic tectum; it receives the lateral lemniscus and projects by way of the brachium of inferior colliculus to the medial geniculate body of the thalamus, and is thus an essential way-station in the central auditory pathway. Synonym: colliculus inferior, corpus quadrigeminum posterius, inferior nasal colliculus, posterior quadrigeminal body. (05 Mar 2000) |
| inferior nasal concha | A thin, spongy, bony plate with curved margins, on the lateral wall of the nasal cavity, separating the middle from the inferior meatus; it articulates with the ethmoid, lacrimal, maxilla, and palate bones, the above bony plate and its thick mucoperiosteum containing an extensive cavernous vascular bed for heat exchange. Synonym: concha nasalis inferior, inferior turbinated bone, turbinated body. (05 Mar 2000) |
| inferior nasal venule of retina | The small vein that passes from the inferior medial (nasal) part of the retina to join the central vein. Synonym: venula nasalis retinae inferior. (05 Mar 2000) |
| inferior nuchal line | A ridge that extends laterally from the external occipital crest toward the jugular process of the occipital bone. Synonym: linea nuchae inferior. (05 Mar 2000) |
| inferior oblique | <anatomy, muscle> Origin, orbital plate of maxilla lateral to the lacrimal groove; insertion, sclera between the superior and lateral recti; action, primary, extorsion; secondary, elevation and abduction; nerve supply, oculomotor (inferior branch). Synonym: musculus obliquus inferior. (05 Mar 2000) |
| inferior oblique muscle of head | <anatomy, muscle> Origin, spinous process of axis; insertion, transverse process of the atlas; action, rotates head; origin, spinous process of axis; insertion, transverse process of the atlas; nerve supply, suboccipital. See: suboccipital muscles. Synonym: musculus obliquus capitis inferior, inferior oblique muscle of head. (05 Mar 2000) |
| inferior occipital gyrus | A gyrus situated below the lateral occipital sulcus on the lower part of the lateral surface of the occipital lobe. (05 Mar 2000) |
| inferior occipital triangle | A triangle with its apex at the external occipital protuberance; its base is formed by a line joining the two mastoid processes. (05 Mar 2000) |
| inferior oesophageal sphincter | A sphincter supposedly present at the oesophagogastric junction; this is in fact an extrinsic sphincter formed by the surrounding musculature of the oesophageal hiagus of the right crus of the diaphragm; causes a normally-occuring constriction at the oesophagogastric junction observable with a barium swallow. Synonym: sphincter constrictor cardiae. (05 Mar 2000) |
| inferior olivary nucleus | A large aggregate of small densely packed nerve cells arranged in folded laminae shaped like a purse with the opening (hilum) directed medially. It corresponds in position to the oliva, projects to all parts of the contralateral half of the cerebellar cortex by way of the olivocerebellar tract, and is the only source of cerebellar climbing fibres. Its afferent connections include fibres from the spinal cord, the dentate nucleus and motor cortex, but its major input appears to be the central tegmental tract originating from multiple nuclei at midbrain levels. Synonym: nucleus olivaris. (05 Mar 2000) |
| inferior olive | <zoology> A genus of polished marine gastropod shells, chiefly tropical, and often beautifully coloured. Origin: L. An olive. Source: Websters Dictionary (01 Mar 1998) |
| inferior omental recess | A recess of the omental bursa extending between anterior and posterior layers of the great omentum. Synonym: recessus inferior omentalis. (05 Mar 2000) |
| inferior ophthalmic vein | <anatomy, vein> Arises from the inferior palpebral and lacrimal veins and divides into two terminal branches, one of which runs to the pterygoid plexus while the other joins the superior ophthalmic vein or empties into the cavernous sinus. Synonym: vena ophthalmica inferior. (05 Mar 2000) |
| inferior orbital fissure | A cleft between the greater wing of the sphenoid and the orbital plate of the maxilla, through which pass the maxillary division and the orbital branch of the trigeminal nerve, fibres from the pterygopalatine (Meckel's) ganglion, and the infraorbital vessels. Synonym: fissura orbitalis inferior, sphenomaxillary fissure. (05 Mar 2000) |