Spinal Cord Anatomy CLOSE
Spinal Tracts Organization
Drawing of a transverse section through half of a spinal cord, illustrating features of spinal tracts. The fasciculus proprius (FP), the collective term for tract fibers that run from one spinal cord segment to another, is immediately adjacent to gray matter. Generally within tracts, tract fibers are organized with the shortest ones closest to gray matter, because new fibers are appended to the deep margin of a particular tract. For example, cervical fibers are deep and sacral region fibers are superficial in the spinothalamic tract. In the case of cranial and caudal branches of primary afferent fibers, branches of pain & temperature nonmyelinated primary afferent axons collect laterally in the dorsolateral fasciculus. Ascending branches of touch & kinesthesia myelinated primary afferent axons are medial in the dorsal funiculus and regionally organized into layers from regions of the body (Ca, S, L, T, & C). Those from the caudal half of the body constitute fasciculus gracilis. Those from the cranial half of the body form fasciculus cuneatus. Lateral and ventral corticospinal tracts are included to depict that tracts consist of a dense core fibers surrounded by a zone of decreasing fiber density.
Go Top