The spinal cord is the extension of the central nervous system that is enclosed in and protected by the vertebral column. The vertebral column consists of 5 segments. From top to bottom those are: the cervical verterbrac the thoracic, the lumbar, the sacrum and the coccyx. It consists of nerve cells and their connections (axons and dendrites), with both gray matter and white matter, with the former surrounded by the latter.
Embryology of the human spinal cord In the fetus, the spinal cord extends all the way down to the sacral vertebrae. As the person matures, the spinal cord shortens relative to the rest of the body, so at adulthood, the spinal cord only reaches up to around the level of L1 (the first lumbar vertebrae[?]) where it terminates and the cauda equina begin - this is why lumbar punctures[?] are usually carried out in the adult at the level of L3/L4.
Anatomy of the human spinal cord It originates in the inferior end of the medulla oblongata, exiting the skull via the foramen magnum[?]. It is wrapped in three layers of membranes, called meninges[?].
The spinal cord carries sensory signals[?] and motor innervation[?] to most of the skeletal muscles[?] in the body. Just about every voluntary muscle[?] in the body below the head depends on the spinal cord for control. Similarly, most cutaneous sensation[?] below the neck is transmitted via the spinal cord. Most of the sympathetic pathways[?] and the lower (i.e. non-vagal) parasympathetic pathways[?] also go through the spinal cord.