The structure and segments of the spinal cord

Nervous system notes complex human organization, the structure and segments of spinal cord clearly show coherence in the work of the authority and its management of the vital processes.


The structure and anatomy of this unique property of the human body has its own characteristics. The external structure of the spinal cord looks like, it resembles an elongated cord, and a cross-section of the spinal cord reaches in various places from one to one and a half inches. He carefully located in the cavity formed by the bodies and vertebrae. The spine protects it from damage, and bone density gives him the location. The ratio of the segments of the spinal cord and divisions of the vertebral column does not correspond to each other, since the length of cord shorter than the vertebral column. Perfect coincidence on the level of the vertebral column was observed only in children aged 5-6 years. Sellotape segments and column of the spine displayed in the diagrams in medical journals.

Spinal cord

Its the beginning of the strand takes in the area of the foramen Magnum of the skull. In fact, the spinal cord is the part of the brain, which goes into the spine and there it ends, therefore, the relationship of the brain and spinal cord is evident. The spinal cord, like the brain, is an integral part of the unified human nervous system. The end of the cord may be noted at the level of the third Department, namely, the first lumbar vertebrae. In this part of the protected strand becomes thinner, forming a brain cone of the spinal cord. Terminal thread size of about 8 cm may end below and to coalesce with the second coccygeal vertebra to the Department.

The length of the spinal cord in newborns is relatively larger than that of a man of Mature age. A child is born with such length of cord, which allows it to end at the level of the third lumbar vertebra. However, during growth at some points it lags nervous system and spinal cord are visually shortened in comparison with the growing vertebrae. The growth of the strand continues until approximately twenty years, after which its final size in length is 43-45 cm Length of the spinal cord in women a couple of inches shorter than men. During this time, the weight increases eight times from the original indicators.

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Spinal cord the human brain is divided into several sections with segments. The number of segments is 32. Each segment controls a specific function of innervation.

The structure of spinal cord consists of five departments. Topography of the spinal cord is represented thus:

The structure of the spine

  • cervical has 8 segments;
  • the chest consists of 12 segments;
  • of the 5 segments consist of the subsequent sections (lumbar and sacral);
  • only segment 2 has a coccygeal Department.

The diameter of the spinal cord in different places is different. The two departments, there is a thickening of the spinal cord, occurring in the first few years of a child’s development because of the increased load on them. Cervical thickening of the spinal cord and lumbar quenching are responsible for motor activity and work of the limbs.

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The internal structure

Строение спинного мозгаThe internal structure of the spinal cord varies. From the beginning to the end of the strand is covered with shells of three layers. The inner shell is called the soft shell. In her column is a set of blood vessels with arteries and veins. They provide the supply of oxygen and nutrients.

The soft shell is arachnoid or arachnoid layer, which contains liquid. It is called the cerebrospinal fluid. For analysis of cerebrospinal fluid sampling of biological material produced from this shell.

The third membrane located on the outer edge is called rigid, and protects the inner shell. It reaches the intervertebral holes. The cord is attached to the vertebrae with ligaments. The Central canal in the spinal cord, extending through the entire length, also filled with liquid.

Furrows and cracks

If you look at the structure of the spinal cord of a person from the outside, you can see that it is riddled with cracks and furrows. They compartmentalise it into two halves. The largest gap – anterior median fissure and posterior. Each half of the spinal cord has grooves separating it into the spinal cords of the brain, or the columns of the spinal cord. All cords, there are three pairs:

The spinal cords of the brain

  • rear cord;
  • anterior cord;
  • the lateral cord.

It is these fibers that are in the cords, are conductors of nervous impulses. For motor function and sensory sensation and meets the spinal cord. With the advent of the abnormalities of certain body functions can fail, so treatment important diagnosis and condition of the spine.

The principle of segmental structure

Already mentioned briefly, spinal cord segments involved in the transmission of nerve impulses to tissues and organs. How does the spinal cord segment is responsible for what each of them?

The structure of the segment of the spinal cord

The structure of the segment of the spinal cord is such that it contains a pair of roots associated with other organs through nerves. Roots leave the spinal canal to form the nerves of themselves that branch out to various tissues and organs. Front and rear roots of the spinal cord are conduits of information. Anterior roots of the spinal cord is formed by the front nerve, they conduct motor information and their main function is stimulation of muscle contraction.

Sensitivity provide back roots, which transmit information from the stimulus via activation of receptors and carry it back to the roots. At the junction of the anterior and posterior roots is spinal ganglion – cluster of neurons located under the protective shell.

The roots out in the holes between the vertebrae, so part of them is exactly at the level, and the other half at an angle. For example, in the cervical spines are arranged horizontally, and the breast – on a slanting line. Other departments are forcing the roots to bend almost straight down. Part of the roots of these divisions is so close to each other that in the photo the beam formed received the name of pony tail in the spinal cord.

Each segment is responsible for its area of innervation. To the area of innervation include the internal organs, bones, muscles and skin. Knowing the area of innervation, it is possible to clearly define which segment of the nerve is responsible for him to assume the pathology of this area. Segmental principle, showing where the cause of pathology helps in the diagnosis and treatment of diseases. Doctors can test exactly the required segment, then to assess the health of the patient. By therapy one or another part of the post can you cure a person from a number of pathologies.

The structure in the context

If you make a cross section of the strand and look at the context, we can see the heterogeneity of its structure. A cross-section of the spinal cord reveals that the cord consists of substances the two colors – white and gray. The gray color is formed by a cluster of neurons, and white – is the accumulation processes of the neurons.

Спинной мозг в разрезеExternally, groups of neurons arranged so that the image of the cut resembles the shape of a butterfly. Here clearly visible convex parts – the front and rear horns of the spinal cord. Photo of some segments received medical researchers, allows you to notice more lateral horns. The front horns contain the nucleus of the spinal cord, and the largest neurons of the spinal cord. They are responsible for movement, and the posterior horn perceive the delicate impulses. The lateral horns of the spinal cord are conductors of the autonomic nervous system. Each segment is clearly responsible for a particular function of the body.

For example, in the last cervical and the first thoracic segment is a set of neurons responsible for innervation of the eye pupils. The third and subsequent cervical segments conduct impulses to the diaphragm, and the first five thoracic segments regulate the activity of the heart. The neurons of the spinal cord from the second to the fifth sacral segment in the Department regulate the operation of the bladder, the same set of segments and innervates the rectum. If people hurt these segments in the case of injury, hemorrhage, inflammation, you may experience problems with defecation and urination. Diagram of the innervation of the segment indicates how tightly it covers all the systems of organs and control them. Have this information is very important for the doctor.

The spinal cord plays an important to the body’s functions – reflex and conductive. It is from the coordinated work of this body depends on the activity of all structures. Physiology of the spinal cord is arranged so that a person has a number of motor reflexes, for example, elbow and knee reflexes. Also the neurons of the brain and spinal cord coordinate complex motor activity of the body. As the spinal cord, the brain involved in the processing of outside signals by means of pulses. The value of the spinal cord is difficult to overestimate, because it is a conduit of information obtained by nerve impulses.