Final answer:
The sacral region of the spinal cord contains a higher proportion of gray matter relative to white matter than other spinal regions. This is due to the characteristics of the sacral region, including the presence of the cauda equina and the distribution of sensory and motor neurons in this area.
Step-by-step explanation:
The question asked about which spinal cord level contains mostly gray matter relative to white matter. The spinal cord regions include cervical, thoracic, lumbar, and sacral. Gray matter consists of cell bodies and interneurons, while white matter contains axons. The sacral region of the spinal cord contains a larger proportion of gray matter relative to white matter compared to other regions. This is partly due to the presence of the cauda equina where the nerves extend, and the spinal cord itself does not grow significantly longer after the first couple of years post-birth.
To summarize this information, remember that the sacral spinal cord segment corresponds to the level at which spinal nerves extend through the intervertebral foramina starting from the upper lumbar vertebral bones. Moreover, cross-sections of the spinal cord, such as those depicted in Figure 13.14, show regions of gray matter that are referred to as horns, with the posterior horn being responsible for sensory processing, the anterior horn for sending out motor signals to skeletal muscles, and the lateral horn (found only in thoracic, upper lumbar, and sacral regions) for housing motor neurons of the autonomic nervous system.