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

Average length in men is 45 cm and in women is 43 cm.

The spinal cord is protected by Bone of the Vertebral Column.

The function of spinal cord is the conduction of impulses from the Brain to the Peripheral Nervous System to 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

 

Starts at the Foramen Magnum and continues to the Conus Medullaris in the back

Fibrous extensions known as Filum Terminale are at the end of the cord.

 

The spinal cord is the only main pathway for information connecting the brain and peripheral nervous system. The length of the spinal cord is much shorter than the length of the bony spinal column. The human spinal cord extends from the foramen magnum and continues through to the conus medullaris near the second lumbar vertebra, terminating in a fibrous extension known as the filum terminale.

It is about 45 cm (18 in) long in men and around 43 cm (17 in) in women, ovoid-shaped, and is enlarged in the cervical and lumbar regions. The cervical enlargement, located from C3 to T2 spinal segments, is where sensory input comes from and motor output goes to the arms. The lumbar enlargement, located between L1 and S3 spinal segments, handles sensory input and motor output coming from and going to the legs.

The spinal cord is protected by three layers of tissue, called spinal meninges, that surround the canal. The dura mater is the outermost layer, and it forms a tough protective coating. Between the dura mater and the surrounding bone of the vertebrae is a space called the epidural space. The epidural space is filled with adipose tissue, and it contains a network of blood vessels. The arachnoid mater is the middle protective layer. Its name comes from the fact that the tissue has a spiderweb-like appearance. The space between the arachnoid and the underlying pia mater is called the subarachnoid space. The subarachnoid space contains cerebrospinal fluid (CSF). The medical procedure known as a lumbar puncture (or “spinal tap”) involves use of a needle to withdraw cerebrospinal fluid from the subarachnoid space, usually from the lumbar region of the spine. The pia mater is the innermost protective layer. It is very delicate and it is tightly associated with the surface of the spinal cord. The cord is stabilized within the dura mater by the connecting denticulate ligaments, which extend from the enveloping pia mater laterally between the dorsal and ventral roots. The dural sac ends at the vertebral level of the second sacral vertebra.

In cross-section, the peripheral region of the cord contains neuronal white matter tracts containing sensory and motor neurons. Internal to this peripheral region is the gray, butterfly-shaped central region made up of nerve cell bodies. This central region surrounds the central canal, which is an anatomic extension of the spaces in the brain known as the ventricles and, like the ventricles, contains cerebrospinal fluid.

The spinal cord has a shape that is compressed dorso-ventrally, giving it an elliptical shape. The cord has grooves in the dorsal and ventral sides. The posterior median sulcus is the groove in the dorsal side, and the anterior median fissure is the groove in the ventral side.

Cervical Segments
-   8 segments that for 8 pairs
-   C1-C8
-   From distal portion of 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 lower back

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

Coccygeal Segment
-   1 Segment

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