The spinal cord is a part of a human organs system that is the most important path for information that connects peripheral nervous system and the brain. Along with the brain, spinal cord is central part of somatic and autonomic nervous system. The spinal cord is shaped like a cylindar tape, about 45 centimeter long in men and 43 in women. It’s surrounded and protected by the bony vertebral column. It’s divided in 2 simetrical parts. Back part is long and shallow and front part looks like a deep crack. Spinal cord (medulla spinalis) consists of grey and white matter. Grey matter is located deep, around spinal cord central canal. In cross section , grey matter looks like a letter H, shaped like a butterfly and formed out of two horns and commissure. There are two types of horns, anterior and posterior. Anterior horn is short and broad. The anterior horn contains motor neurons which joined together affect the axial muscles. Cell bodies of alpha motor neurons are placed in the anterior horn. Posterior horn of spinal cord is narrow and long. It receiver different types of sensory information from the body such as proprioception, vibration., touch, sensation. Top of the posterior horn is extended with gelatin substance that contains number of neuroglia cells and neurons. Grey commisure, which consist of little nerve cells, contains centers of autonomic nervous system.White matter of the spinal cord is at the surface and it is divided by grey matter horns and spinal nerve roots into 3 so called bundles: frontal, side and back. Front ones are conncected with thick commissure. Back ones are divided by glial compartment. Spinal nerves get off with two roots that branch of the spinal cord and connect again passing out through a hole in each of the vertebrae named Foramen (foramen interventerbrale). Frontal Root contains Motor fibres and the back one contains sensitive nerve fibres.
There are four groups of spinal nerves and they are:
- Cervical nerves – C
- Thoracic nerves – T
- Lumbar nerves – L
- Sacral nerves – S
Cervical nerves are nerves in the neck. Thiracic nerves are nerves in the upper back, and Lumbar and Sacral are nerves in the lower back. There are 31 pairs of spinal nerves.