Final answer:
The bulge in the spinal cord giving off nerves to the lower limbs is known as the lumbar enlargement, which has a greater population of motor neurons for the numerous muscles in the lower limbs.
Step-by-step explanation:
The bulge in the spinal cord that gives off nerves to the lower limbs is called the lumbar enlargement. This region of the ventral (anterior) horn of the spinal cord contains a larger population of motor neurons due to the greater number of muscles found in the lower limb. The lumbar enlargement allows for innervation and movement control of the lower extremities.
It's important to note that the cervical enlargement is also a significant area in the spinal cord, particularly large because of the greater control needed over the fine musculature of the upper limbs, especially the fingers. In contrast, the lumbar enlargement is not as prominent visually, indicating less fine motor control required for the lower limbs but still quite critical for lower limb function.
The influence of these enlargements on the appendicular muscles means that the lateral corticospinal tract is especially significant for controlling the movements of the arms and legs, where the ventral horns in both the cervical and lumbar spinal cord regions are wider, representing the extensive number of muscles commanded by these motor neurons.