| fourth finger | Fourth finger. Synonym: digitus annularis, fourth finger. (05 Mar 2000) |
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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) |
| 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) |
| anvil sound | In cases of a large pulmonary cavity or of pneumothorax, a clear metallic sound obtained by striking a coin, held against the chest, by another coin, or by flicking the chest wall with one's fingernail; the sound is heard on auscultating the chest wall on the same side anteroposteriorly. Synonym: anvil sound, bell sound, coin test. (05 Mar 2000) |
| atrial 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) |
| auscultatory sound | A rale, murmur, bruit, fremitus, or other sound heard on auscultation of the chest or abdomen. (05 Mar 2000) |
| bell sound | In cases of a large pulmonary cavity or of pneumothorax, a clear metallic sound obtained by striking a coin, held against the chest, by another coin, or by flicking the chest wall with one's fingernail; the sound is heard on auscultating the chest wall on the same side anteroposteriorly. Synonym: anvil sound, bell sound, coin test. (05 Mar 2000) |
| Campbell sound | A miniature sound with a short round-tipped beak, especially curved for the deep urethra of the young male. (05 Mar 2000) |
| cannon sound | The loud first heart sound heard intermittently in complete atrioventricular block and in interference-dissociation when the ventricles happen to contract shortly after the atria. Synonym: cannon sound. (05 Mar 2000) |
| cardiac sound | The sounds heard over the cardiac region produced by the functioning of the heart. There are four distinct sounds: the first occurs at the beginning of systole and is heard as a "lubb" sound; the second is produced by the closing of the aortic and pulmonary valves and is heard as a "dupp" sound; the third is produced by vibrations of the ventricular walls when suddenly distended by the rush of blood from the atria; and the fourth is produced by atrial contraction and ventricular filling but is rarely audible in the normal heart. The physiological concept of heart sounds is differentiated from the pathological heart murmurs. (12 Dec 1998) |