Final answer:
In adults, the spinal cord ends between the L1 and L2 vertebrae, with the nerves extending below this level known as the cauda equina.
Step-by-step explanation:
In adults, the spinal cord (conus medullaris) ends between the first and second lumbar vertebrae, which are represented as L1 and L2, respectively. Below this level, the spinal cord does not contain spinal nerves anymore, but the nerves continue as a bundle called the cauda equina. These nerves exit the spinal column at the levels appropriate for their destinations in the body. The spinal cord is protected by the vertebral column, which consists of 26 bones: 24 vertebrae, the sacrum, and the coccyx, divided into cervical (C1-C7), thoracic (T1-T12), and lumbar (L1-L5) regions.