Anatomy of Spinal Cord

Spinal cord connects body and the brain. It is the main super highway that transmits nerve impulses. It takes sensory impulses from the sense organs, into the brain and takes the commands, from the brain into the muscles. Thirty one pairs of spinal nerves are attached to the spinal cord.

Spinal cord is situated within the vertebral column and it is continuous with the medulla oblongata (hind brain) and ends as a bunch of spinal nerves called cauda equina. As in the brain it is covered with meninges.

It is a 3cm diameter cylindrical tube. In an adult human it is around 45cm long. It starts in the foramen magnum of the skull and ends at the level of third lumbar vertebra.

What are the things seen in a cross section?

Spinal cord consists of central grey matter and peripheral white matter. White matter is nerve fibers and grey matter is neuron cell bodies. Central grey matter is arranged as a letter H. All the other areas consist of white matter.

At the center of the spinal cord there is a hollow cylindrical cavity called the central canal. It is filled with cerebro – spinal fluid. In the anterior surface of the spinal cord there is a groove called the ventral median sulcus. Also in the posterior surface there is another groove called dorsal sulcus.

What are the areas in the white matter?

White matter inside the spinal cord is divided into three sections called dorsal, lateral and ventral areas (funiculi).

Descending motor pathways primarily responsible for fine motor skills are located mainly in the lateral areas. Motor pathways that are responsible for gross motor movements and balance are located in the ventral area. Fibers transmitting pain, temperature and simple touch can be found in both ventral and lateral areas.

What are the areas in the grey matter?

Grey matter is arranged as a letter H in a cross section. Four arms of the grey matter (similar to letter H) are divided as two ventral horns and two dorsal horns. Cross bar of the letter “H” is called the intermediate zone.

Dorsal horns are the sites of spinal sensory nerve entry.  These sensations are carried out into the brain. Ventral horns consist of the cell bodies of the nerves that send the main motor output.

Intermediate zone consists of interneurons that are responsible for the modulation of sensory and motor transmission. They also play major part in spinal reflexes.