The spinal cord
Definition
Is an elongated cylindrical part of the central nervous system which is suspended in the vertebral canal
It is covered by the meninges and cerebrospinal fluid.
Extent
It is continuous above with the medulla oblongata
It extends from the upper border of the atlas to the lower border of the 1st lumbar vertebra.
45 cm
Thickness of the little finger
Functional anatomy
It is a nervous link between the brain and the body
It has communicating nerve tracts
The nerve tracts carry impulses to and from the brain
At times the neurones in the spinal cord act independently of the cerebral cortex - spinal reflexes
Structure
Two equal parts
Anteriorly median fissure
Posteriorly deep median septum
Composed of central grey matter
Surrounded by white matter and neuroglia
Grey matter
H - shaped
Two posterior, two anterior and two lateral columns
The central transverse commisure is pierced by the central canal - the continuation of the fourth ventricle of the brain.
Central canal contains the cerebrospinal fluid.
The cell bodies are : sensory cells, lower motor neurones and connector neurones - connecting the sensory and motor neurones ® spinal reflex arcs
Posterior columns of grey matter
Composed of cell bodies - sensory - their neve fibres form the white matter of the cord
transmits sensory impulses to the brain
Anterior columns of grey matter
cell bodies of the lower motor neurones - get stimulated by axons of upper motor neurones or the connector neurones
White matter
Arranged in anterior, posterior and lateral tracts - sensory - ascend to the brain. also has motor fibres descending from the brain
Spinal nerves
31 pairs of spinal nerves issue from the spinal cord - pass through the intervertebral foramina.
