| fourth finger | Fourth finger. Synonym: digitus annularis, fourth finger. (05 Mar 2000) |
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| fourth heart sound | The sound produced in late diastole in association with ventricular filling due to atrial systole and related to reduced ventricular compliance. It is a low frequency oscillation that may be normal at older ages owing to a physiologic decline in ventricular compliance but is nearly always abnormal at younger ages if it is of high intensity or palpable. It is common in ventricular hypertrophy, particularly with hypertension, and is almost invariable during acute myocardial infarction. Fourth heart sounds may arise from the right or left ventricle or both. Synonym: atrial sound. (05 Mar 2000) |
| 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) |
| 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 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) |
| anterior carpal region | The anterior part of the wrist. Synonym: regio carpalis anterior. (05 Mar 2000) |
| palmar carpal branch of radial artery | <anatomy, artery> A small branch of the radial artery that passes medially across the wrist to supply the carpal joints; it anastomoses with the anterior carpal branch of the ulnar artery. Synonym: ramus carpalis palmaris arteriae radialis, ramus carpeus palmaris arteriae radialis. (05 Mar 2000) |
| palmar carpal branch of ulnar artery | <anatomy, artery> A branch of the ulnar artery that supplies the carpal joints and communicates with the anterior carpal branch of the radial artery. Synonym: ramus carpalis palmaris arteriae ulnaris, ramus carpeus palmaris arteriae ulnaris. (05 Mar 2000) |
| palmar carpal ligament | Thickening of distal antebrachial fascia just proximal to radiocarpal (wrist) joint. Continuous with extensor retinaculum at margins of forearm. This structure is distinct from the transverse carpal ligament, commonly called "the flexor retinaculum," which forms the roof of the carpal tunnel. Synonym: flexor retinaculum of forearm, palmar carpal ligament. (05 Mar 2000) |
| carpal | Relating to the carpus. (05 Mar 2000) |
| carpal arches | Two anastomotic arterial twigs running transversely across the wrist: the palmar or anterior lies in front of the carpus, being formed by palmar carpal branches of the radial and ulnar arteries; the dorsal or posterior lies on the dorsal surface of the carpus, being formed by the dorsal carpal branches of the radial and ulnar arteries. (05 Mar 2000) |
| carpal artery | <anatomy, artery> Arteries related to and supplying the wrist joint. See: dorsal carpal branch of radial artery, dorsal carpal branch of ulnar artery, palmar carpal branch of radial artery, palmar carpal branch of ulnar artery. (05 Mar 2000) |