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Spinal Cord

The Spinal Cord is a bundle of nerves that are centrally involved in the Central Nervous System. The “cord” is a long but thin bundle of tissue and cells that starts at the Medulla Oblongata of the Brain and descends to the lower back.

The cord does not extend the entire length of the Vertebral Column and ends between the 1st and 2nd Lumbar Vertebrae. The Average length in men is 45 cm and in women is 43 cm. It is protected by Bone of the Vertebral Column.

The function of the spinal cord is the conduction of impulses from the Brain to the Peripheral Nervous System to the extremities and back again. The Nervous System is an important aspect of human function and movement.

There are 31 segments of the spinal cord.

Every segment has several nerves that branch out on the left and right sides of the vertebral column.

Nerve types of the spinal cord are divided into 3 categories:

1.)  Motor – Ventral

–  Information travels down from the brain

2.)  Sensory – Dorsal

–  Sensory information from the extremities and such are gathered and sent back up to the brain to be processed.

3.)  Mixed

–  Reflexes of the nervous system

Structure of the Spinal Cord

The spinal cord starts at the Foramen Magnum and continues to the Conus Medullaris in the back. There are fibrous extensions known as Filum Terminale is at the end of the cord.

The cord is the main pathway for information to be transmitted via the nerves connecting the brain and the peripheral nervous system.

The spinal cord is protected by three layers of tissue, called Spinal Meninges that surround the canal.

1.)  The Dura Mater is the outermost layer

2.)  The Arachnoid Mater is the middle protective layer

3.)  The Pia Mater is the underlying protective layer

Segments of the Spine

Cervical Segments
–  8 segments for 8 pairs
–  C1-C8
–  From the distal portion of the skull
–  Forms the neck region

Thoracic Segments
–  12 segments
–  T1-T12
–  From below neck region to mid-back

Lumbar Segments
–  5 Segments
–  L1-L5
–  Mid back towards the lower back

Sacral Segments
–  5 Segments
–  S1-S5
–  Lower back

Coccygeal Segment
–  1 Segment