Spinal Cord & Brainstem Sections
Overview: Below are transverse sections from 20 levels of the spinal cord and brainstem. The sections begin at the sacral cord and move rostrally to the rostral midbrain. Our goal is to provide an overall summary of the spinal and brainstem structures that we describe in NBIO 401. Below is a section from nearly the most caudal part of the cord. In this section and the following sections we show the level of the section with a red line on an image to the left. We also name the level of the sections in the upper left. For the cord, the section in the center is stained for fibers. The hemi-section to the right is stained for cells. (You ...view middle of the document...
Your goal here is to be able to identify the level of the cord that a section comes based on what the section looks like. Above you see spinal cord sections that are roughly scaled to size. Imagine that these sections are in the "prone" position and that you are looking at them from their caudal surface, that is, you are looking up the CNS in the rostral direction. Thus dorsal (posterior, the back of the person) is at the top of section and the left side (of the person) is to your left. Cord sections: upper left -- cervical enlargement; upper right -- thoracic; lower left -lumbar; lower right -- sacral. Identify the gray matter and white matter groups on each
section. Note that the proportion of white to gray is greater in the cervical cord segments than in sacral segments, because all descending and ascending tracts must pass through the cervical level to reach their targets. (White matter in the sacral cord contains only descending tracts that end in gray matter in the sacral segments, and ascending tracts carrying information from sacral spinal nerves). The thoracic cord section has the least amount of gray matter compared to the cervical or lumbosacral regions. Gray matter is expanded in the cervical and lumbosacral regions to accommodate the neurons responsible for innervating the limbs.
-Appendix, brainstem sections, page 4-
The differences in the size and shape of the gray matter at different spinal levels are emphasized on the next page where we see outlines of gray matter at different spinal levels. The gray matter illustrated here was traced from a set of human spinal cord sections. Note the increase in the size and lateral extent of the gray matter (particularly in the anterior [ventral] horns) in the cervical (C5-T1) and lumbar (L2-S2) regions. These enlargements accommodate additional neurons for processing the output (and input) required for the innervation of the upper and lower extremities respectively. Note that the thoracic cord innervates the trunk, and remains much the same size from segment to segment (segments T7-T9 are not...