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The spinal cord is a slender cylindrical structure about the size of
the little finger. The spinal cord begins immediately below the brain
stem and extends to the first lumbar vertebra. Thereafter, the cord blends
with the conus medularis which becomes the cauda equina,
a group of nerves resembling the tail of a horse.
The spinal nerve roots are responsible for stimulating movement and
feeling. The nerve roots exit the spinal canal through the intervertebral
foramen, small hollows between each vertebra.
The brain and the spinal cord make up the Central Nervous System
(CNS). The nerve roots that exit the spinal cord/spinal canal branch out
into the body to form the Peripheral Nervous System (PNS).
Table 1
| Type of Neural Structure |
Role/Function |
| Brain Stem |
Connects the spinal cord to other parts
of the brain. |
| Spinal Cord |
Carries nerve impulses between the brain
and spinal nerves. |
| Cervical Nerves (8 pairs) |
These nerves supply the head, neck, shoulders,
arms, and hands. |
| Thoracic Nerves (12 pairs) |
Connects portions of the upper abdomen
and muscles in the back and chest areas. |
| Lumbar Nerves (5 pairs) |
Feeds the lower back and legs. |
| Sacral Nerves (5 pairs) |
Supplies the buttocks, legs, feet, anal
and genital areas of the body. |
| Dermatomes |
Areas on the skin surface supplied by nerve
fibers from one spinal root. |
 | 1 Sciatic Nerve (yellow)
2 Part of the Sacrum
3 Hip Bone |
Between the front and back portions of
the vertebra (i.e. the mid-region) is the spinal canal that houses
the spinal cord and the intravertebral foramen. The foramen
are small hollows formed between each vertebra. These "hollows" provide
space for the nerve roots to exit the spinal canal and to further branch
out to form the peripheral nervous system.
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