| fourth ventricle | A cavity of irregular tentlike shape extending from the obex rostralward to its communication with the sylvian aqueduct, enclosed between the cerebellum dorsally and the rhombencephalic tegmentum ventrally, having a rhomboid-shaped floor (rhomboid fossa) and a tentlike roof which in its caudal part is formed by the tela choroidea and the posterior medullary velum, in its middle part by the white matter of the cerebellum, and in its narrowing rostral part (recessus superior) by the anterior medullary velum. The fourth ventricle reaches its greatest width at the pontomedullary transition, where it expands laterally behind the cerebellar peduncles into the spoutlike lateral recess, and its greatest height at the fastigial recess, which reaches up into the cerebellar white matter. Direct communication of the brain's ventricle system and the subarachnoid space is established at the level of the fourth ventricle by a median opening in the tela choroidea, the medial aperture of Magendie's foramen, which opens into the cerebellomedullary cistern, and on both sides by the lateral aperture or foramen of Luschka, which connects the lateral recess with the interpeduncular cistern. Synonym: ventriculus quartus, ventricle of rhombencephalon. (05 Mar 2000) |
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| fourth ventricle mass | <radiology> IN ADULTS: choroid plexus papilloma, haemangioblastoma, vermian metastasis, arteriovenous malformation (AVM), inflammatory mass/cyst IN KIDS: medulloblastoma, uniform enhancement, homogeneous, ependymoma, patchy enhancement, heterogeneous, calcified (12 Dec 1998) |
| lateral recess of fourth ventricle | The narrow recess of the ventricle that extends laterally over, and down along the side of, the inferior cerebellar peduncle and the overlying cochlear nuclei; at its tip it opens by way of Luschka's foramen into the interopeduncular cistern of the subarachnoid space. By way of this recess, part of the choroid plexus of the fourth ventricle protrudes into the subarachnoid space. Synonym: recessus lateralis ventriculi quarti. (05 Mar 2000) |
| lateral vein of lateral ventricle | A vein draining deep portions of the temporal and parietal lobes; it runs in the lateral wall of the lateral ventricle to terminate in the superior thalamostriate vein. Synonym: vena ventriculi lateralis lateralis, lateral atrial vein, lateral vein of lateral ventricle. (05 Mar 2000) |
| lateral ventricle | A cavity shaped somewhat like a horseshoe in conformity with the general shape of the hemisphere; each lateral ventricle communicates with the third ventricle through the interventricular foramen of Monro, and expands from there forward into the frontal lobe as the anterior horn as well as caudally over the thalamus as the central part or cella media which, behind the thalamus, curves ventrally and laterally, then forward into the temporal lobe as the inferior horn; from the apex of the curve a variably sized posterior horn extends back into the white matter of the occipital lobe. The large choroid plexus of the lateral ventricle invades the cella media and the inferior horn (but not the anterior and posterior horn) from the medial side. Synonym: ventriculus lateralis, ventricle of cerebral hemisphere. (05 Mar 2000) |
| left ventricle | <anatomy> The muscular chamber of the heart which accepts blood from the left atrium and ejects it into the aorta to the systemic circulation. (27 Sep 1997) |
| abnormal heart chamber dimensions | <radiology> Left ventricular volume overload, left ventricular hypertrophy, right ventricular volume overload, right ventricular hypertrophy, fixed subvalvular aortic stenosis, hypoplastic left/right ventricle; common ventricle, congestive cardiomyopathy (12 Dec 1998) |
| Abrams' heart reflex | A contraction of the myocardium when the skin of the precordial region is irritated. (05 Mar 2000) |
| american heart association | A voluntary organization concerned with the prevention and treatment of heart and vascular diseases. (12 Dec 1998) |
| apex of heart | The blunt extremity of the heart formed by the left ventricle. See: apex beat. Synonym: apex cordis, vertex cordis. (05 Mar 2000) |
| armored heart | Calcareous deposits in the pericardium due to subacute or chronic pericarditis. Synonym: panzerherz. (05 Mar 2000) |
| armor heart | Extensive to complete calcification (rarely ossification) of the pericardium usually producing constrictive pericarditis. (05 Mar 2000) |
| artificial heart | A mechanical pump used to replace the function of a damaged heart, either temporarily or as a permanent prosthesis. (05 Mar 2000) |
| artificial heart valve | <cardiology> A synthetic or porcine (pigskin) valve surgically placed into the heart to replace a defective or malfunctioning valve. The aortic and mitral valves are the most frequently replaced with artificial valves. (27 Sep 1997) |
| athlete's heart | A more or less loose designation for cardiac findings in healthy athletes that would be or could be abnormal in patients with disease, including atrioventricular blocks, left ventricular hypertrophy and, sometimes, benign arrhythmias and atrioventricular blocks. (05 Mar 2000) |