| anterior centriole | The centriole that lies in a depression in the wall of the posterior portion of the nucleus of the developing spermatozoon. Synonym: anterior centriole. (05 Mar 2000) |
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| anterior cerebellar notch | A wide, shallow notch on the anterior surface of the cerebellum occupied laterally by the superior cerebellar peduncles and the inferior quadrigeminal bodies medially. Synonym: anterior notch of cerebellum, incisura cerebelli anterior, semilunar notch. (05 Mar 2000) |
| anterior cerebral artery | <anatomy, artery> One of the two terminal branches (with middle cerebral artery) of the internal carotid; it passes anterior, loops around the genu of the corpus callosum then posteriorly in the interhemispheric fissure along with its fellow of the opposite side, the two being joined by the anterior communicating artery; for descriptive purposes it is divided into two parts: the precommunical part (A2 segment of clinical terminology), supplying branches to the thalamus and corpus striatum, and the postcommunical part, (A2) or pericallosal artery, supplying branches to the cortex of the medial parts of the frontal and parietal lobes. Synonym: arteria cerebri anterior. (05 Mar 2000) |
| anterior cerebral vein | <anatomy, vein> A small vein that parallels the anterior cerebral artery and drains into the basal vein. Synonym: vena cerebri anterior. (05 Mar 2000) |
| anterior chamber | The space in the eye, filled with aqueous humor, bounded anteriorly by the cornea and a small portion of the sclera and posteriorly by a small portion of the ciliary body, the iris, and that part of the crystalline lens which presents through the pupil. (12 Dec 1998) |
| anterior chamber cleavage syndrome | <syndrome> A congenital disorder originating from faulty separation of embryonic structures; it results in bilateral central corneal opacities, with an anterior ring attachment of the iridic pupillary border and anterior polar cataracts; associated with short-limbed dwarfism; autosomal dominant inheritance. See: iridocorneal endothelial syndrome. Synonym: Peters' anomaly. (05 Mar 2000) |
| anterior chamber of eye | The space between the cornea anteriorly and the iris/pupil posteriorly, filled with a watery fluid (aqueous humor) and communicating through the pupil with the posterior chamber. Synonym: camera anterior bulbi, camera oculi anterior, camera oculi major. (05 Mar 2000) |
| anterior chamber trabecula | Tissue at the angle of the anterior chamber through which aqueous humor exits from the eye. (05 Mar 2000) |
| anterior choroidal artery | <anatomy, artery> Origin, internal carotid or (rarely) middle cerebral artery; distribution, optic tract, crus cerebri, uncus, hippocampus, globus pallidus, posterior part of internal capsule, geniculate bodies of the thalamus, and choroid plexus in the inferior horn of the lateral ventricle. Synonym: arteria choroidea anterior. (05 Mar 2000) |
| anterior choroiditis | Disseminated choroiditis restricted to peripheral choroid. (05 Mar 2000) |
| anterior ciliary artery | <anatomy, artery> One of several arteries derived from muscular branches of the ophthalmic which perforate the anterior part of the sclera and anastomose with posterior ciliary arteries. Synonym: arteria ciliaris anterior. (05 Mar 2000) |
| anterior circumflex humeral artery | <anatomy, artery> Origin, axillary; distribution, shoulder joint and biceps muscle; anastomoses, posterior circumflex humeral artery. Synonym: arteria circumflexa humeri anterior, anterior humeral circumflex artery. (05 Mar 2000) |
| anterior clear space | On lateral chest radiographs, the region dorsal to the sternum and ventral to the ascending aorta. Synonym: anterior clear space. (05 Mar 2000) |
| anterior column | The pronounced, ventrally oriented ridge of gray matter in each half of the spinal cord; it corresponds to the anterior or ventral horn appearing in transverse sections of the cord, and contains the motor neurons innervating the skeletal musculature of the trunk, neck, and extremities. See: gray columns. Synonym: columna anterior. (05 Mar 2000) |
| anterior column of medulla oblongata | An elongated, white prominence on the ventral surface of the medulla oblongata on either side along the anterior median fissure, corresponding to the pyramidal tract. Synonym: pyramis medullae oblongatae, anterior column of medulla oblongata, anterior pyramid. (05 Mar 2000) |