Spinal cord: located inside the vertebrae
The interior of the vertebrae (some of them) contain a nerve mass, divided into two regions: gray and white.
The spinal cord is called the set of neurons that make up these masses, which have distinct functions, which will be known below.
It is a structure measuring 45 cm and starts in the foramen magnum, extending to L1 (first lumbar vertebral).
Spinal Cord Regions:
It is composed, as mentioned before, by two regions:
- White matter: divides into funicles, and contain axons.
- Gray matter: houses the neuronal nuclei, which are organized according to their functions (sensory and motor).
The main “segments” and divisions present are:
- Anterior midline fissure: divides the anterior funicles;
- Posterior median sulcus: divides the posterior funicles;
- Gray commissure: anterior and posterior to the central canal;
- Central canal: where there is cerebrospinal fluid;
- Horns: anterior, posterior and central; each with distinct nerve fibers.
The spine, which even contains the spinal cord, is covered by 3 meninges - structures that stabilize and protect the spinal cord and all the nerves involved. They are: dura mater, pia mater and arachnoid.
There are also marrow thickening in some regions, which are called swelling. They contain interneurons, with the function of transmitting sensory signals and coordinating motor neurons. There are two: cervical and lumbar swelling.
Spinal nerve pairs
There are 31 spinal nerves, corresponding to 31 spinal segments. Are they:
- Eight cervicals;
- Twelve thoracic;
- five lumbar;
- Five sacrals;
- One corresponding to the coccyx.
The spinal cord houses several nerve structures and therefore has functions such as:
- Transmission and processing of sensory information of limbs and trunk.
- Involvement in the transmission and regulation of viscera signals.
- Control of body movements through the circuits with the muscles.
- Spinal cord injuries can result in both loss of motion and sensitivity. In some cases, the picture may be reversed over time.
- Even after its termination, the medulla continues as a terminal filament after L1.
- The reflex arc is a nervous circuit, which does not require information to be processed in the brain. A sensory neuron is activated, there is synapse in the medulla, and motor neuron efference responsible for the response.
- There are a number of other reflexes, which involve different synapse numbers, and can be tested by physical examination.
Last reviewed: 12/17/2018
By Elaine Barbosa de Souza
Undergraduate student in Biological Sciences, Methodist University of São Paulo.