| 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) |
|---|---|
| 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) |
| absolute terminal innervation ratio | The number of motor endplates divided by the number of terminal axons related to them. (05 Mar 2000) |
| amino-terminal | <biochemistry> The end of a protein or polypeptide chain with the unattached amino group or the aminoacyl residue containing it. Each amino acid in the chain has an amino group on one side, which is attached to the carboxyl group (COOH group) of the previous amino acid, and a carboxyl group on the other side (which is attached to the amino group of the next amino acid). The other end of the polypeptide chain is called the carboxyl terminal. Synonym: NH2-terminal. (14 Aug 2000) |
| amino-terminal residue | <biochemistry> The only amino acid residue in a polypeptide chain that has a free alpha-amino group, it defines the amino terminus of the polypeptide. (09 Oct 1997) |
| axonal terminal boutons | The somewhat enlarged, often club-shaped endings by which axons make synaptic contacts with other nerve cells or with effector cells (muscle or gland cells). As isolated, by homogenizing brain or spinal cord, they contain acetylcholine and the related enzymes. Terminals contain neurotransmitters of various kinds, sometimes more than one. These can be demonstrated by chemical analysis and immunocytochemical methods. See: synapse. Synonym: axonal terminal boutons, end-feet, neuropodia, pieds terminaux, synaptic boutons, synaptic endings, synaptic terminals, terminal boutons, bouton terminaux. (05 Mar 2000) |
| carboxyl terminal | The end of a polypeptide chain with the unattached carboxyl group (a -COOH group). Each amino acid in the middle of the chain has an amino group (a -NH2 group) on one side (which is attached to the carboxyl group of the previous amino acid) and a carboxyl group on the other side (which is attached to the amino group of the next amino acid). The other end of the polypeptide chain is called the amino terminal. (09 Oct 1997) |
| carboxyl-terminal residue | This amino acid residue defines the carboxylterminus of the polypeptide, its the only residue with a free alpha-carboxyl group. (09 Oct 1997) |
| carboxy terminal | The end of a peptide or protein having a free carboxyl (-COOH) group. (05 Mar 2000) |
| carboxy-terminal domain kinase | <enzyme> Protein kinase that phosphorylates the c-terminal repeat domain of the largest subunit of RNA polymerase II at serine residues Registry number: EC 2.7.1.- Synonym: ctd kinase, hs-ctd kinase, tfiih-associated ctd kinase (26 Jun 1999) |
| central terminal electrode | In electrocardiography, an electrode in which connections from the three limbs (right arm, left arm, and left leg) are joined and led to the electrocardiograph to form the indifferent electrode, theoretically at zero potential for the system. (05 Mar 2000) |