The spinal cord is located inside the vertebral canal, which is formed by the foramina of 7
cervical, 12 thoracic, 5 lumbar, and 5 sacral vertebrae, which together form the spine. It extends
from the foramen magnum down to the level of the first and second lumbar vertebrae (at birth,
down to second and third lumbar vertebrae).
The spinal cord is composed of 31 segments: 8 cervical (C), 12 thoracic (T), 5 lumbar (L), 5
sacral (S), and 1 coccygeal (Co), mainly vestigial. The spinal nerves comprise the sensory nerve
roots, which enter the spinal cord at each level, and the motor roots, which emerge from the cord
at each level. The spinal nerves are named and numbered according to the site of their emergence
from the vertebral canal. C1-7 nerves emerge above their respective vertebrae. C8 emerges
between the seventh cervical and first thoracic vertebrae. The remaining nerves emerge below
their respective vertebrae.
The dorsal rami of C1-4 are located in the suboccipital region. C1 participates in the innervation
of neck muscles, including the semispinalis capitis muscle. C2 carries sensation from the back of
the head and scalp along with motor innervation to several muscles in the neck. C3-C5
contribute to form the phrenic nerve and innervate the diaphragm. C5-T1 provide motor control
for the upper extremities and related muscles.
The thoracic cord has 12 segments and provides motor control to the thoracoabdominal
The lumbar and sacral portions of the cord have 5 segments each. L2-S2 provide motor control
to lower extremities and related muscles.
The conus medullaris is the cone-shaped termination of the caudal cord. The pia mater continues
caudally as the filum terminale through the dural sac and attaches to the coccyx. The coccyx has
only one spinal segment. The cauda equina (Latin for horse tail) is the collection of lumbar and
sacral spinal nerve roots that travel caudally prior to exiting at their respective intervertebral
foramina. The cord ends at vertebral levels L1-L2.
Meninges of the spinal cord
Spinal cord was wearing three connective shells, meninges. Shells are the following, if you go
from the surface inwards: dura mater, dura mater; arachnoid, arachnoidea, and soft shell, ria
mater. Cranial all 3 shell are continuing in the same shell of the brain.
Dura mater of the spinal cord, dura mater spinalis, covers in the form of the bag outside the
spinal cord. It is not fitted close to the walls of the spinal canal, which are covered by
periosteum. The latter is also called the outer layer of hard shell. Between the periosteum and the
solid shell is epiduralyyue space, cavitas epiduralis. In it lie fatty tissue and venous plexus,
plexus vendsi vertebrales interni, which flows into the venous blood from the spinal cord and
Cranial dura mater merges with the edges of large holes occipital bone and the caudal ends at the