Spinal cord

The spinal cord is an elongated, thin and tube-like structure of a collection of the nervous tissues and support cells which extends from the medulla oblongata. It starts at the occipital bone down to the gap in the 1st and 2nd lumbar vertebrae but not stretching to the full length of the vertebral column.

The protecting longer bony structure that encloses the spinal cord is called vertebral column.

The central nervous system is made up of the spinal cord and the brain.

Structure
The length of spinal cord in men is around 18 inches or 45 centimeters. In women, it is around 17 inches or 43 centimeters.

The width of the spinal cord also varies. In cervical and lumbar regions, it is ½ inch thick and in the thoracic region, it is ¼ inch thick. This enlargement in the cervix paves the way for sensory input and motor output from and to the arms. The enlargement in the lumbar is in charge of the sensory input and motor output from and to the legs.

It is sheltered by 3 layers of tissue known as spinal meninges which covers the canal.

The outermost layer, the dura mater, is the first hard protective covering. The gap between the dura mater and nearby vertebrae bone is called the epidural space. It contains adispose tissue which is made up of a network of blood vessels.

The mid-protective layer is called the arachnoid mater. As the name implies, this tissue layer has a spider-like form. The gap between the arachnoid and the third layer is referred as the subarachnoid space. The gap contains the cerebrospinal fluid. And the third protective layer is called the pia mater, a delicate tissue closely associated to the surface of the cord.

What make the spinal cord stable are the denticulate ligaments within the dura mater. It stretches from the pia mater sideways between the ventral and dorsal roots.

In the cross-section minor region of the cord, there are the neuronal white matter tracts which contains the motor and sensory neurons. In the central region is a gray butterfly-shaped area made of nerve cell bodies which surrounds the central canal. It is an extension of the ventricles which also contains the cerebrospinal fluid.

Function
The primary function of the spinal cord is as the passageway of information to and from the brain and nervous system. Aside from transmitting neural signals from the brain to the whole body, it can also control many reflexes and central pattern generators through neural circuits.

Specifically, the spinal cord has 3 functions:

Medium for motor information which travels down in the cord

Medium for sensory information which travels up to the brain

Coordination center for some reflexes