The spinal cord is a part of the central nervous system characterized by a long and thin bundle of tissues and cells that extends to the medulla. This and the brain make up the CNS, or the central nervous system. Its length is extended to the space of the first and second lumbar vertebrae, but does not extend until the vertebral column.
It is made up primarily of gray matter and is located in the spinal column. It is for the body and the brain to communicate, allowing coordination. The tracts of white matter that are situated peripherally are the ones that send a variety of impulses to and fro the brain. The length of the spinal cord is similar to the thorax and is connected to the brain through the foramen magnum of the skull. It has two basic, yet very vital functions:
- It is responsible for the impulses that result in neural communication to and fro the brain, and also with the entire human body. Peripheral sensory receptors in the entire body is sent back to the brain for interpretation. The tracts which are descending then send motor impulses to the glands or the muscles to be able to respond to the stimuli.
- It is also involved in the reflexes going on in the spine. Pathways of the dedicated nerves directly determine the reflex from the spinal cord, making it possible for the voluntary actions to receive information without taking so much time and distance.
The spinal cord could be seen running to the first vertebrate at the same level, if it is extended to the inferior side (the one near
the foramen magnum situated in the occipital bone). Because of its posteroventral shape which is slightly flattened, it would look like an ovular cross section.
If it is viewed posteriorly, the two enlargements in the spinal cord could be seen- particularly the cervical enlargement between the second thoracic vertebrate and the third cervical vertebrate. It is from that area of the spinal cord where the upper extremities get then nerve supply.
The spinal cord is created by 31 segments. Each of these has a pair of spinal nerves which is pushed outward from the spinal cord through the intervertebral foramina. There are also 2 two distinct channels that slightly separate the spinal cord into two: the general left and right side. These 2 distinct channels are called the posterior median sulcus and the anterior median fissure.
There are also three meninges protecting the brain, the spinal cord and the cerebrospinal fluid. The pia mater supply oxygen and blood to the cells. Most of the parts in the spinal cord are made up with gray matter, and is also encompassed by white matter. The gray matter, which makes up the majority of the spinal cord is made up of neuroglia, unmyelinated association neurons and nerve cell bodies. The white matter on the other hand is composed of myelinated fibers that brings the motor and sensory neurons. At the core of the gray matter, it will form the letter H. It has paired horns that extend posteriorly, and it is called the posterior horns. On the other hand, the horns that extends anteriorly is called to anterior horns.
There is also a pair of lateral horns that could be seen projecting forward to the sides. In the lumbar and thoracic areas, the lateral horns could be seen, however, it will not be visible to other regions. These horns are united across the middle part of the spinal cord by a gray matter known to be the gray commissure. This is where the central canal lies. The gray commissure is extended until the ventricles of the brain, with the cerebrospinal fluid protecting it.
On the other hand, the columns of white matter in the spinal cord has tracts which ascend and descend for the travel of the nerve impulses, making it possible to deliver messages to the body structure or to the brain. In the spinal cord, there are 6 columns of white matter named the funiculli, and they are named according to their position. The anterior funiculli are situated on both sides of the anterior median fissure. In the same manner, the posterior funiculli are also placed on the gray matter’s posterior horns.
The individual funiculli are the ones that line up in the ascending and descending tracts. Its nerve fibers are myelinated, and names according to its location. Fibers in these tracts remain on the same side or cross over the spinal cord (and even in medulla oblongata). This crossing over is called decussation. Take for instance corticospinal tracts. They continuously descend in the absence of a synaptic interruption. The fibers for these tracts are created by the frontal lobe, particularly the precentral gyrus. Around 85 percent of these undergo decussation, and the remaining percentage makes up the anterior corticospinal tracts.
The remaining nerve tracts are called the extrapyramidial tracts. These originate in the brain stems. A variety of synaptic connections cause the cerebral cortex, the cerebellum, and the basic nuclei to produce motion indirectly.