The spinal cord is one of the departments of the central nervous system (central nervous system) that connects the body with the external environment and regulates its functions. Thanks to the central nervous system, various human organs and systems act in concert, responding to changes that occur in the external environment.
The connection of the brain with organs and limbs is carried out using the spinal cord. It performs conductor and reflex functions.
How is the spinal cord arranged and where?
The structure of this CNS department is relatively simple. The spinal cord is formed by gray and white matter. White matter is a complex system of nerve fibers (myelin and non-myelin), nerve tissue, and blood vessels that are slightly surrounded by connective tissue. Gray matter is formed by the bodies of nerve cells with processes that do not have a myelin sheath. A canal runs through the center of the spinal cord, which is filled with cerebrospinal fluid. With the internal organs and limbs it is connected by numerous nerves, which are characterized by the correct frequency of exit.
The width of the spinal cord in an adult reaches one and a half centimeters, the length is 45 cm. Its average weight is 35 g.
The human spinal cord is located in the internal cavity of the spinal canal. Outwardly, it resembles a long cord with numerous branches. Its upper end without a sharp boundary is connected with the medulla oblongata in the region of the I cervical vertebra, the lower is located at the level of I – II lumbar vertebrae. It goes into the terminal (spinal) thread. The upper sections of the terminal thread have fragments of nerve tissue, but otherwise it is a connective formation. Penetrating the dura mater into the sacral canal, the spinal cord is attached at its end.
There are three shells surrounding the spinal cord. The inner shell is soft (vascular), the middle is arachnoid and the outer is hard. From the membranes to the bone canal there are ligaments that hold the spinal cord in a constant position. The space between the inner and middle membranes fills the cerebrospinal fluid.
Thus, the cavity of the spinal canal, where the spinal cord is located, is filled with adipose tissue, cerebrospinal fluid, the membranes of the brain, as well as blood vessels.
Longitudinal grooves divide the spinal cord into right and left symmetrical halves.
In the spinal canal, nerve roots pass at a short distance. They come from each half, forming two longitudinal rows. They leave the spinal canal through foraminar openings. The spinal cord is characterized by pronounced segmentality. Segments belong to that part of the brain in which the nerves emanating from them leave the spinal canal. Each segment innervates a particular area of the human body.
Five parts of the spinal cord are isolated. The cervical part is formed by eight segments, the thoracic - twelve segments, the lumbar - five, the sacral - also five, the coccygeal - 1-3 segments. Segments of the cervical part innervate the arms and neck, the thoracic part - the chest and abdomen, the lumbar and sacral - legs, pelvic organs and perineum. Nerve roots extending below the end of the spinal cord innervate the lower half of the body, including the pelvic organs.
A disorder in the sensitivity or motor function of a particular area of the body may indicate that part of the spinal cord in which damage could occur.
The peripheral nerves from the spinal cord to the organs of the body receive nerve impulses. They regulate the functions of all organs. Sensitive nerve fibers transmit information from tissues and organs to the spinal cord and central nervous system.