Final answer:
The opening through which spinal nerves branch out from the spinal cord is known as the intervertebral foramen, and there are 31 pairs of spinal nerves corresponding to various levels of the spinal column.
Step-by-step explanation:
Spinal Nerves and Intervertebral Foramen
The opening through which spinal nerves pass after branching from the spinal cord is called the intervertebral foramen. Each spinal nerve emerges from the spinal column through this passageway at its respective level. Specifically, there are 31 pairs of spinal nerves, corresponding to the levels of the spinal cord: eight cervical (C1-C8), twelve thoracic (T1-T12), five lumbar (L1-L5), five sacral (S1-S5), and one coccygeal (Co1). As the bones of the spine, or vertebrae, grow, so do these nerves, trailing with the vertical column and passing through the intervertebral foramen.
Additionally, it's noteworthy that while the foramen magnum is a large opening that allows the brain to connect to the spinal cord, the intervertebral foramen are the notches through which the spinal nerves travel to serve different levels of the body. It is the elongation of these nerves alongside the growing vertebral column that forms the cauda equina, resembling a horse's tail, at the base of the spinal column.