| longitudinal relaxation | In nuclear magnetic resonance, the return of the magnetic dipoles of the hydrogen nuclei (magnetization vector) to equilibrium parallel to the magnetic field, after they have been flipped 90 |
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| longitudinal section | A section that is cut along the long axis of a structure. The opposite is a cross-section. (12 Dec 1998) |
| longitudinal sinus | See: inferior sagittal sinus, superior sagittal sinus. Longitudinal vertebral venous sinus, large, plexiform veins forming portions of the anterior internal vertebral venous plexus lying on the posterior surfaces of the vertebral bodies on either side of the posterior longitudinal ligament. Synonym: sinus vertebrales longitudinales. Luschka's sinus, venous sinus in the petrosquamous suture. (05 Mar 2000) |
| longitudinal studies | Studies in which variables relating to an individual or group of individuals are assessed over a period of time. (12 Dec 1998) |
| longitudinal study | <epidemiology> A study taking place over time. If individuals are followed, this is a longitudinal cohort study. If individuals are not followed, but classes (usually age classes) are restudied, this is a longitudinal cross-sectional study. The converse of a horizontal study. (05 Dec 1998) |
| longitudinal sulcus of heart | See: anterior interventricular groove, posterior interventricular groove. (05 Mar 2000) |
| longitudinal wave | <physics> Waves where the variation of the field is partially or totally in the direction of propagation (parallel to wavennumber, k [a vector]). Examples include sound waves and Langmuir waves. Contrasted with transverse waves, where the variation is perpendicular to the direction of propagation, such as light waves. (13 Nov 1997) |
| abdominal internal oblique muscle | <anatomy, muscle> Origin, iliac fascia deep to lateral part of inguinal ligament, anterior half of crest of ilium, and lumbar fascia; insertion, tenth to twelfth ribs and sheath of rectus; some of the fibres from inguinal ligament terminate in the conjoint tendon; action, diminishes capacity of abdomen, flexes lumbar vertebral column (bends thorax forward); nerve supply, lower thoracic. Synonym: musculus obliquus internus abdominis, abdominal internal oblique muscle. (05 Mar 2000) |
| anterior intercostal branches of internal thoracic artery | One of the arteries supplying the anterior portions of the intercostal spaces of the thoracic wall. Anterior intercostal arteries 1-6 arise as branches of the internal thoracic artery; 7-11 arise as branches of the musculophrenic artery. Synonym: rami intercostales anteriores, rami intercostalis anteriores arteria thoracica interna. (05 Mar 2000) |
| anterior limb of internal capsule | The portion of the internal capsule between the head of the caudate nucleus and the putamen; it lies anterior to the genu of the internal capsule. Synonym: crus anterius capsulae internae. (05 Mar 2000) |
| aponeurosis of internal abdominal oblique muscle | <anatomy> Broad, flat tendinous portion of the internal abdominal oblique muscle. The fleshy fibres of the muscle end in the aponeurosis lateral to the semilunar line. The uppermost portion of the aponeurosis is attached to the outer surfaces and lower borders of the seventh to ninth costal cartilages. Of the portion extending between the costoxiphoid margin and the pubis, the upper two-thirds splits into anterior and posterior laminae at the lateral border of the rectus abdominis muscle to contribute to the anterior and posterior walls of the sheath of the rectus abdominis muscle as they extend to the midline linea alba. The lower third of the aponeurosis does not split but joins the aponeuroses of the external abdominal oblique and transversus abdominis muscles to form the anterior wall of the sheath of the rectus abdominis muscle. The fibres of the portion of the aponeurosis contributing to the rectus sheath decussate with those of the contralateral aponeurosis in the linea alba. The lowermost portion of the aponeurosis blends with the aponeurosis of the transversus abdominis muscle to form the conjoint tendon, attaching to the pubic crest and often the pecten pubis, thus forming the posterior wall of the inguinal canal at the superficial inguinal ring. See: cremasteric fascia, conjoint tendon, rectus sheath. (05 Mar 2000) |
| basal tentorial branch of internal carotid artery | <anatomy, artery> A small branch from the cavernous part of the internal carotid artery to the base of the tentorium. Synonym: ramus basalis tentorii arteriae carotidis internae. (05 Mar 2000) |
| ganglionic branch of internal carotid artery | <anatomy, artery> Branch to trigeminal ganglion; a small branch of the cavernous part of the internal carotid artery to the trigeminal ganglion. Synonym: ramus ganglii trigeminalis. (05 Mar 2000) |
| marginal tentorial branch of internal carotid artery | <anatomy, artery> A small branch from the cavernous part of the internal carotid artery to the free margin of the tentorium. Synonym: ramus marginalis tentorii arteriae carotidis internae. (05 Mar 2000) |
| genu of internal capsule | The obtuse angle, opening laterally in the horizontal plane, formed by the union of the two limbs (crus anterius and crus posterius) of the internal capsule. Synonym: genu capsulae internae. (05 Mar 2000) |