tract (trakt)
1. a region, principally one of some length.
2. a bundle of nerve fibers having a common origin, function, and termination.
3. a number of organs, arranged in series and serving a common function.
alimentary tract see under canal.
atriohisian tracts myocardial fibers that bypass the physiologic delay of the atrioventricular node and connect the atrium directly to the bundle of His, allowing preexcitation of the ventricle.
biliary tract the organs, ducts, etc., participating in secretion (the liver), storage (the gallbladder), and delivery (hepatic and bile ducts) of bile into the duodenum.
digestive tract alimentary canal.
dorsolateral tract a group of nerve fibers in the lateral funiculus of the spinal cord dorsal to the posterior column.
extracorticospinal tract , extrapyramidal tract extrapyramidal system.
Flechsig's tract posterior spinocerebellar t.
gastrointestinal tract the stomach and intestine in continuity.
genitourinary tract urogenital system.
Gowers' tract anterior spinocerebellar t.
iliotibial tract a thickened longitudinal band of fascia lata extending from the tensor muscle downward to the lateral condyle of the tibia.
intestinal tract the small and large intestines in continuity.
nigrostriatal tract a bundle of nerve fibers extending from the substantia nigra to the globus pallidus and putamen in the corpus striatum; injury to it may be a cause of parkinsonism.
optic tract the nerve tract proceeding backward from the optic chiasm, around the cerebral peduncle, and dividing into a lateral and medial root, which end in the superior colliculus and lateral geniculate body, respectively.
pyramidal tract two groups of nerve fibers arising in the brain and passing down through the spinal cord to motor cells in the anterior horns.
respiratory tract see under system.
reticulospinal tract a group of fibers arising mostly from the reticular formation of the pons and medulla oblongata; chiefly homolateral, the fibers descend in the ventral and lateral funiculi to most levels of the spinal cord.
spinocerebellar tract, anterior a group of nerve fibers in the lateral funiculus of the spinal cord, arising mostly in the gray matter of the opposite side, and ascending to the cerebellum through the superior cerebellar peduncle.
spinocerebellar tract, posterior a group of nerve fibers in the lateral funiculus of the spinal cord, arising mostly from the nucleus thoracicus, and ascending to the cerebellum through the inferior cerebellar peduncle.
spinothalamic tract a group of nerve fibers in the lateral funiculus of the spinal cord that arise in the opposite gray matter and ascend to the thalamus, carrying the sensory impulses activated by pain and temperature.
urinary tract
1. see under system.
2. sometimes more specifically the conduits leading from the pelvis of the kidneys to the urinary meatus.
urogenital tract see under system.
uveal tract the vascular tunic of the eye, comprising the choroid, ciliary body, and iris.
re·tic·u·lo·spi·nal tract (r -tk y -l -sp  nl)n. Any of several fiber tracts descending to the spinal cord from the reticular formation of the pons and medulla oblongata. Some fibers conduct impulses from the neural mechanisms regulating cardiovascular and respiratory functions to the spinal cord; others form links in extrapyramidal motor mechanisms affecting muscle tonus and somatic movement. |
reticulospinal tract
spinal cord tract originating in the reticular formation in the brainstem and impinging on motor fibers arising in the spinal cord.
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