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| fourth lumbar nerve | <anatomy, nerve> The ventral branch of the nerve is forked to enter into the formation of both lumbar and sacral plexuses. Synonym: furcal nerve, nervus furcalis. (05 Mar 2000) |
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| fourth parallel pelvic plane | The lower opening of the true pelvis, bounded anteriorly by the pubic arch, laterally by the rami of the ischium and the sacrotuberous ligament on either side, and posteriorly by these ligaments and the tip of the coccyx. Synonym: apertura pelvis inferior, apertura pelvis minoris, fourth parallel pelvic plane, pelvic outlet, pelvic plane of outlet, plane of outlet. (05 Mar 2000) |
| fourth stage of labour | The hour or two after delivery when the tone of the uterus is established and the uterus contracts down again. (12 Dec 1998) |
| fourth turbinated bone | A small concha frequently present on the posterosuperior part of the lateral nasal wall; it overlies the supreme nasal meatus. Synonym: concha nasalis suprema, fourth turbinated bone, highest concha, highest turbinated bone, Santorini's concha, concha santorini, supraturbinal, supreme concha, supreme turbinated bone, turbinated body. (05 Mar 2000) |
| 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) |
| basal part of pulmonary artery | <anatomy, artery> See: right pulmonary artery, left pulmonary artery. (05 Mar 2000) |
| cavernous part of internal carotid artery | <anatomy, artery> The tortuous portion of the internal carotid artery located within the cavernous sinus; it has numerous small branches. Synonym: pars cavernosa arteriae carotidis internae. (05 Mar 2000) |
| cerebral part of internal carotid artery | <anatomy, artery> The portion of the internal carotid artery that supplies the brain; its branches are: superior hypophyseal, clival, ophthalmic, anterior choroidal, anterior cerebral, and middle cerebral. Synonym: pars cerebralis arteriae carotidis internae. (05 Mar 2000) |
| cervical part of internal carotid artery | <anatomy, artery> The unbranched portion located in the neck. Synonym: pars cervicalis arteriae carotidis internae. (05 Mar 2000) |
| petrous part of internal carotid artery | <anatomy, artery> The part of the internal carotid artery in the carotid canal; its branches are carotidotympanic arteries and the artery of the pterygoid canal. Synonym: pars petrosa arteriae carotidis internae, petrous bone. (05 Mar 2000) |
| cortical part of middle cerebral artery | <anatomy, artery> See: middle cerebral artery. Synonym: pars corticalis arteriae cerebralis mediae. (05 Mar 2000) |
| postcommunical part of anterior cerebral artery | <anatomy, artery> The continuation of the anterior cerebral artery after the anterior communicating artery; it supplies branches to the cerebral cortex as it passes along the corpus callosum. Synonym: pars postcommunicalis arteria cerebri anterior, arteria pericallosa, postcommunical part of anterior cerebral artery. (05 Mar 2000) |
| precommunical part of anterior cerebral artery | precommunical part of anterior cerebral artery |