| LRT | local radiation therapy; long terminal repeat; lower respiratory tract |
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| LST | lateral spinothalamic tract; left sacrotransverse [fetal position]; life-sustaining treatment |
| LVOH | left ventricle outflow [tract] height |
| LVOT | left ventricular outflow tract |
| LVST | lateral vestibulospinal tract |
| supraopticohypophysial tract | A bundle of unmyelinated fibres originating from all cells of the supraoptic nucleus and an estimated 20% of those of the paraventricular nucleus of the hypothalamus, which extend through the infundibulum and pituitary stalk to their endings in the posterior lobe of the hypophysis; the fibres convey neurosecretory substances, vasopressin and oxytocin, which are stored in (and can be released into the circulating blood from) their terminals. See: hypophysis, neurosecretion. Synonym: tractus supraopticohypophysialis, hypothalamohypophysial tract. (05 Mar 2000) |
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| deiterospinal tract | A somatopically organised fibre bundle originating from the lateral vestibular nucleus (nucleus of Deiters) which descends uncrossed into the anterior funiculus of the spinal cord lateral to the anterior median fissure; the tractus extends throughout the length of the cord, distributing fibres at all levels to the medial part of the anterior horn. Excitatory impulses conveyed by the vestibulospinal tract increase extensor muscle tone. Synonym: tractus vestibulospinalis, deiterospinal tract. (05 Mar 2000) |
| dentatothalamic tract | That component of the superior cerebellar peduncle (brachium conjunctivum) which originates in the cerebellar nuclei, crosses completely in the decussation of the brachia conjunctiva, bypasses the red nucleus, and terminates in parts of the ventral anterior, ventral intermediate, ventral posterolateral, and central lateral nuclei of the thalamus. Synonym: tractus cerebellothalamicus, dentatothalamic tract. (05 Mar 2000) |
| descending tract of trigeminal nerve | <anatomy, nerve> A compact fibre bundle, comma-shaped on transverse section, composed of primary sensory fibres of the portio major of the trigeminal nerve, descending from the level of the entrance of the trigeminus in the upper pons down through the dorsolateral region of the rhombencephalic tegmentum along the lateral side of the descending or spinal nucleus of the trigeminus, emerging on the dorsolateral surface of the lower medulla oblongata as the tuberculum cinereum, and continuing as far as the second cervical segment of the spinal cord. Its fibres are distributed to the descending or spinal nucleus of the trigeminus. Synonym: tractus spinalis nervi trigemini, descending tract of trigeminal nerve, tractus descendens nervi trigemini. (05 Mar 2000) |
| digestive tract | The passage leading from the mouth to the anus through the pharynx, oesophagus, stomach, and intestine. Synonym: alimentary canal, alimentary tract, digestive tube, tubus digestorius. (05 Mar 2000) |
| direct pyramidal tract | Uncrossed fibres forming a small bundle in the pyramidal tract. See: pyramidal tract. Synonym: tractus corticospinalis anterior, tractus pyramidalis anterior, anterior corticospinal tract, anterior pyramidal fasciculus, direct pyramidal tract, fasciculus corticospinalis anterior, fasciculus pyramidalis anterior, Turck's bundle, Turck's column, Turck's tract. (05 Mar 2000) |
| dorsolateral tract | A longitudinal bundle of thin, unmyelinated and poorly myelinated fibres capping the apex of the posterior horn of the spinal gray matter, composed of posterior root fibres and short association fibres that interconnect neighboring segments of the posterior horn. Synonym: fasciculus dorsolateralis, tractus dorsolateralis, dorsolateral tract, fasciculus marginalis, Lissauer's bundle, Lissauer's column, Lissauer's fasciculus, Lissauer's marginal zone, Lissauer's tract, marginal fasciculus, Spitzka's marginal tract, Spitzka's marginal zone, Waldeyer's tract, Waldeyer's zonal layer. (05 Mar 2000) |
| iliopubic tract | Thickened inferior margin of the transversalis fascia seen as a fibrous band running parallel and posterior (deep) to the inguinal ligament, contributing to the posterior wall of the inguinal canal as it bridges the external iliac-femoral vessels from the iliopectineal arch to the superior pubic ramus. It marks the inferior edge of the deep inguinal ring and the medial margin of the femoral canal. Seen only when the inguinal region is viewed from its internal aspect, it is a useful landmark in laparoscopy of this region, as for repair of inguinal herniae. Synonym: deep crural arch, Thompson's ligament. (05 Mar 2000) |
| iliotibial tract | A fibrous reinforcement of the fascia lata on the lateral surface of the thigh, extending from the crest of the ilium to the lateral condyle of the tibia. Synonym: tractus iliotibialis, iliotibial band, Maissiat's band. (05 Mar 2000) |
| infection, urinary tract | An infection in the urinary system that begins when microorganisms cling to the opening of the urethra (the canal from the bladder) and begin to multiply. most utis are due to one type of bacteria, e. (escherichia) coli, a normal denisen of the colon. An infection in the urethra leads to inflammation called urethritis. From there bacteria may move up, causing a bladder infection (cystitis) and if the infection is not treated promptly, bacteria may go up the ureters to infect the kidneys (pyelonephritis). Factors leading to uti include any abnormality of the urinary tract (such as a urinary tract malformation or a kidney stone) that obstructs the flow of urine, an enlarged prostate gland that slows the flow of urine, catheters (tubes) in the bladder, diabetes (due to changes of the immune system), and any disorder that suppresses the immune system. Women have more uti than men, probably because a woman's urethra is shorter (allowing bacteria quick access to the bladder) and nearer sources of bacteria from the anus and vagina. For many women, sexual intercourse seems to trigger an infection, as may the use of a diaphragm. Not everyone with a uti has symptoms but symptoms commonly include a frequent urge to urinate and a painful, burning when urinating (dysuria). The urine may look milky or cloudy, even reddish if blood is present. Kidney infection can cause pain in the back or side below the ribs. In children, symptoms may be easily missed or misunderstood. A child with a uti may be irritable, not eat normally, have an unexplained fever, have incontinence or loose bowels, or just not thrive. (12 Dec 1998) |
| intestinal tract | <anatomy> This includes the coarse of the small and large intestines and includes approximately 27 feet of bowel. (27 Sep 1997) |
| occipitocollicular tract | The system of nerve fibres by which the occipital cortex projects to the superior colliculus. Synonym: occipitocollicular tract. (05 Mar 2000) |
| occipitopontine tract | A group of fibres originating in the occipital lobe of the cerebral hemisphere and descending in the internal capsule and lateral part of the crus cerebri to the pontine nuclei or ventral part of the pons. Synonym: tractus occipitopontinus. (05 Mar 2000) |
| occipitotectal tract | The system of nerve fibres by which the occipital cortex projects to the superior colliculus. Synonym: occipitocollicular tract. (05 Mar 2000) |
| olfactory tract | A nervelike, white band composed primarily of nerve fibres originating from the mitral cells and tufted cells of the olfactory bulb but also containing the scattered cells of the anterior olfactory nucleus. The tract is closely applied to the ventral surface of the frontal lobe, and attaches itself to the base of the cerebral hemisphere at the olfactory trigone, beyond which it extends in the form of the olfactory striae which distribute their fibres to the olfactory tubercle and, in largest number, to the olfactory cortex on and around the uncus of the parahippocampal gyrus. See: olfactory nerves. Synonym: tractus olfactorius, olfactory peduncle. (05 Mar 2000) |