Spinal cord

Spinal cord (medulla spinalis) is a bundle of brain tissue, which is located in the spinal canal. The length of an adult reaches 41-45 cm, and width - 1-1.5 cm

Upper spinal cord smoothly passes into the medulla oblongata (medulla oblongata) of the brain. The lower part of the spinal cord, gradually thinned, level II lumbar vertebra forms the brain cone (conus medullaris), which is in the form of a rudimentary spinal cord, called the terminal filament (filum terminale), continues down penetrating the sacral canal, and attached to the periosteum of the coccygeal vertebrae II. In places of exit of the nerves to the limbs formed cervical enlargement (intumescentia cervicalis) and in the upper lumbar enlargement (intumescentia lumbalis) in the lower section.

In Fig. 250.
The spinal cord is a rear view
1 - the medulla oblongata;
2 - cervical enlargement;
3 - spinal nerves;
4 - cervical nerves;
5 - rear middle slit;
6 - Rear lateral sulcus;
7 - thoracic nerves;
8 - lumbar enlargement;
9 - cerebral cone;
10 - lumbar nerves;
11 - sacral nerves;
12 - coccygeal nerve;
13 - terminal thread
 

The front surface of the spinal cord is slightly concave and extending the entire length of the deep anterior midline cleft (fissura mediana ventralis), located on the back of the narrow posterior median sulcus (sulcus medianus dorsalis). Crack and fissure divide the spinal cord into symmetrical halves. On either side are the roots of spinal nerves of the brain (nn. spinales). The anterior roots (radix ventralis) are formed from the axons of motor nerve cells in and out of brain tissue in the anterior lateral sulcus (sulcus lateralis anterior). Posterior roots (radix dorsalis) are formed by sensory neurons and spinal cord are on the back of the lateral sulcus (sulcus lateralis posterior). Without going outside the spinal canal, motor and sensory roots coalesce and form a mixed pair of spinal nerves. Spinal nerves pass between adjacent vertebrae and sent to the periphery. Spinal canal is longer than the spinal cord that is caused by a higher intensity of growth of bone tissue compared to brain. Therefore, in the lower regions of nerve rootlets are almost vertical.

The internal structure of the spinal cord discernible in cross section. In the center of H-shaped gray matter is located, which is surrounded by white matter.

Gray matter of spinal cord (substantia grisea medullae spinalis) is formed by the bodies of neurons. In the center of the spinal cord along its entire length is a central channel (canalis centralis), filled with cerebrospinal fluid. On each side of the gray substance forms on the three tabs that form the pillars of gray (columnae griseae), high visibility at a volume reconstruction. When a cross-section out two rear horns (cornu dorsale) of gray matter in sensory neurons that end, and two front horns (cornu ventrale), which are the body of motor cells. Half of the gray matter connected with each other bridge of gray matter, which is called the central intermediate substance (substantia intermedia centralis). The plot of gray matter in conjunction with its corresponding two roots form a segment of the spinal cord. In humans emit eight cervical segments, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal.

In Fig. 251.
Volumetric reconstruction of the spinal cord
1 - the white matter;
2 - gray matter;
3 - Rear (sensitive) spine;
4 - spinal nerves;
5 - anterior (motor) root;
6 - spinal ganglion

White matter of spinal cord (substantia alba medullae spinalis) is formed by processes of nerve cells, whose bodies are located in different parts of the nervous system, and is a non-segmented portion of the spinal cord, the surrounding gray matter. It consists of two halves, linked together by a thin white soldering (commissura alba).

In Fig. 252.
Spinal cord cross-section
1 - back cord;
2 - posterior horn;
3 - lateral cord;
4 - center channel;
5 - white commissure;
6 - front horn;
7 - anterior cord

Set of processes of nerve cells, unidirectional conducting impulses, that is, only tactile or motor only, and passing through the spinal cord in special channels, called pathways. In white matter there are three pairs of spermatic cord: front, side and rear (funiculi anterior, lateralis et posterior). Front cords located between the front columns of gray matter, together with the lateral cord, which lie between the anterior and posterior poles, wires contain two types: bottom-up guides are sent to various departments of the central nervous system (CNS), top-down wires coming from different entities to the motor cells of the CNS the spinal cord. Rear cords are located between the rear pillars and contain rising conductors who travel to the cerebral cortex, responsible for conscious evaluation of the body in space, that is, joint and muscle sense.

In addition to the wiring of the function, the spinal cord is responsible for the reflex activity (eg, tendon knee-jerk). When it occurs with the closure of the neural circuits at the level of the respective segments.





List of Abbreviations

a., aa. — arteria, arteriae (artery, the artery)

lig., ligg. — ligamentum, ligamenta (ligament, the ligaments)

m., mm. — musculus, musculi (muscle, the muscle)

n., nn. — nervus, nervi (nerve, the nerve)

r., rr. — ramus, rami (branch)

s. — seu (or)

v., vv. — vena, venae (vienna)