| 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) |
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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) |
| abductor muscle of great toe | <anatomy, muscle> Origin, medial process of calcaneal tuberosity, flexor retinaculum, and plantar aponeurosis; insertion, medial side of proximal phalanx of great toe; action, abducts great toe; nerve supply, medial plantar. Synonym: musculus abductor hallucis, abductor muscle of great toe. (05 Mar 2000) |
| abductor muscle of little toe | Origin, lateral and medial processes of calcanean tuberosity; insertion, lateral side of proximal phalanx of fifth toe; action, abducts and flexes little toe; nerve supply, lateral plantar nerve. Synonym: musculus abductor digiti minimi pedis, abductor muscle of little toe, musculus abductor digiti quinti. (05 Mar 2000) |
| adductor muscle of great toe | <anatomy, muscle> Origin, by two heads, the transverse head from the capsules of the lateral four metatarsophalangeal joints and the oblique head from the lateral cuneiform and bases of the third and fourth metatarsal bones; insertion, lateral side of base of proximal phalanx of great toe; action, adducts great toe; nerve supply, lateral plantar. Synonym: musculus adductor hallucis, adductor muscle of great toe. (05 Mar 2000) |
| blue toe syndrome | <syndrome> Atherothrombotic microembolism of the lower extremities due to recurrent cholesterol embolic 'showers' with painful cyanotic discoloration of the toes and embolism to other sites that completely resolve between attacks. Despite the gangrene-like appearance, blue toes may respond to conservative therapy without amputation. (12 Dec 1998) |
| bursa of great toe | The bursa between the lateral side of the base of the first metatarsal bone and the medial side of the shaft of the second metatarsal. (05 Mar 2000) |
| painful toe | A condition, usually associated with flatfoot, in which walking causes severe pain in the metatarsophalangeal joint of the great toe. Synonym: painful toe. (05 Mar 2000) |
| Goldstein's toe sign | <clinical sign> Increased space between the great toe and its neighbor, seen in mongolism and occasionally in cretinism. (05 Mar 2000) |