| longitudinal ligaments | Two extensive fibrous bands running the length of the vertebral column. The anterior longitudinal ligament (ligamentum longitudinale anterius; lacertus medius) interconnects the anterior surfaces of the vertebral bodies; the posterior longitudinal ligament (ligamentum longitudinale posterius) interconnects the posterior surfaces. The commonest clinical consideration is ossification of posterior longitudinal ligament. (12 Dec 1998) |
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| longitudinal magnification | <microscopy> A certain distance, measured axially, in the object space as referred to the respective distance in the image space. The ratio of the distance D' in the image space to the distance D in the object space equated to the square of the linear magnification M of the system. Thus: M exp2 =D'/D. (05 Aug 1998) |
| longitudinal method | In developmental psychology, the study of the life span of one individual involving comparisons of different age levels. Compare: cross-sectional method. (05 Mar 2000) |
| longitudinal oval pelvis | A pelvis in which the anteroposterior diameter is longer than the transverse. Synonym: longitudinal oval pelvis. (05 Mar 2000) |
| longitudinal pontine bundles | The massive bundles of corticofugal fibres passing longitudinally through the ventral part of pons; they are composed of corticopontine, corticobulbar, and corticospinal fibres. Synonym: fasciculi longitudinales pontis, longitudinal pontine bundles. (05 Mar 2000) |
| longitudinal pontine fasciculi | The massive bundles of corticofugal fibres passing longitudinally through the ventral part of pons; they are composed of corticopontine, corticobulbar, and corticospinal fibres. Synonym: fasciculi longitudinales pontis, longitudinal pontine bundles. (05 Mar 2000) |
| 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 |
| 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) |
| longitudinalis | The word come from the Latin longitudo meaning length. Hence, longitudinal means along the length, running lengthwise, or (by extension) over the course of time. (12 Dec 1998) |
| superior longitudinal sulcus | The groove in the midline of the inner table of the calvaria lodging the superior sagittal sinus. Synonym: sulcus sinus sagittalis superioris, sagittal groove, sagittal sulcus, superior longitudinal sulcus. (05 Mar 2000) |
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| dorsal longitudinal fasciculus | A bundle of thin, poorly myelinated nerve fibres reciprocally connecting the periventricular zone of the hypothalamus with ventral parts of the central gray substance of the midbrain. Synonym: fasciculus longitudinalis dorsalis, Schutz' bundle, tract of Schutz. (05 Mar 2000) |
| inferior longitudinal fasciculus | A well marked bundle of long association fibres running the whole length of the occipital and temporal lobes of the cerebrum, in part parallel with the inferior horn of the lateral ventricle. Synonym: fasciculus longitudinalis inferior. (05 Mar 2000) |
| inferior longitudinal muscle of tongue | An intrinsic muscle of the tongue, cylindrical in shape, occupying the underpart on either side; action, shortens the lower part of the tongue; nerve supply, motor by hypoglossal, sensory by lingual. Synonym: musculus longitudinalis inferior, inferior lingual muscle. (05 Mar 2000) |
| inferior longitudinal sinus | An unpaired dural venous sinus in the lower margin of the falx cerebri, running parallel to the superior sagittal sinus and merging with the great cerebral vein to form the the straight sinus. Synonym: sinus sagittalis inferior, inferior longitudinal sinus. (05 Mar 2000) |
| ossification of posterior longitudinal ligament | Ossification or calcification of the posterior longitudinal ligament of the spinal column. The main symptoms arise from myelopathy of various degrees of severity, usually spinal cord compression caused by stenosis of the spinal canal. It is very common in the japanese but relatively less common in caucasians. It is frequently, but not exclusively, located at the level of the cervical spine. It is often associated with anterior ankylosing hyperostosis. (12 Dec 1998) |
| lateral longitudinal arch of foot | Formed by calcaneus, cuboid and two lateral metatarsals; the combined arch is supported normally by ligaments, intrinsic muscles, and the tendons of extrinsic muscles of the foot. Synonym: arcus pedis longitudinalis pars lateralis. (05 Mar 2000) |
| lateral longitudinal stria | A thin longitudinal band of nerve fibres accompanied by gray matter, near each outer edge of the upper surface of the corpus callosum under cover of the cingulate gyru. Synonym: stria longitudinalis lateralis, stria tecta, tectal stria. (05 Mar 2000) |