The medulla

The medulla (medulla oblongata, s. bulbus medullae spinalis, s. myelencephalon) - rear diamond-shaped brain (rhombencephalon).
Morphology. Is located in the medulla between the spinal cord and the bridge (Fig. 1 and 2). The border with the spinal cord is determined by the place of an exit of the first pair of cervical nerves and the bottom edge of the decussation of the pyramids (decussatio pyramidum), the border with the bridge of a brain - the appearance of transverse fibers bridge (fibrae pontis transversae). In the field of diamond-shaped holes (fossa rhomboidea) border of the medulla oblongata is determined medullary or hearing strips (striae medullares ventriculi quarti). Diamond-shaped brain, which includes the medulla and the bridge, saves mostly common with the spinal cord plan of structure, however, has a number of distinctive features. It is particularly important that the Central configuration of the cavity of the diamond-shaped brain changes: it greatly widened, forming the diamond-shaped hole, the bottom of which is occupied by motor, visceral and sensitive kernel, and motor kernel shifted to the middle line, sensitive - outwardly, and visceral - located between them.

Fig. 1. The brain stem (the front surface):
1 - n. oculomotorius;
2 - n. trochlearis;
3 - gangi. trigeminale;
4 - n. trigeminus (rad. motoria);
5 - n. trigeminus (rad. sensoria);
6 - n. abducens;
7 - n. facialis;
8 - n. vestibulocochlearis;
9 - n. glossopharyngeus;
10 - n. vagus;
11 - n. hypoglossus;
12 - n. accessorius;
13 - III spinal spine (cervical I);
14 - bottom surface of cerebellar hemispheres;
15 - anterior median fissure medulla oblongata;
16 - sulcus lateralis ant.;
17 - decussatio pyramidum;
18 - pons;
19 - pedunculus cerebri.

Fig. 2. The brain stem (back):
1 - bottom of the fourth ventricle;
2 - n. trochlearis;
3 - n. facialis;
4 - n. intermedius;
5 - n. vestibulocochlearis;
6 - n. glossopharyngeus;
7 - n. vagus;
8 - n. accessorius;
9 - tuberculum nucl. cuneati;
10 - tuberculum nucl. gracilis;
11 - sulcus lateralis post.;
12 - fasciculus cuneatus;
13 - sulcus intermedius post.;
14 - fasciculus gracilis;
15 - fissura mediana post.;
16 - calamus scriptorius (BNA);
17 - striae medullares ventriculi quarti;
18 - pedunculus cerebellaris inf.

In contrast to spinal cord, medulla oblongata, and of the whole brain, characterized by the absence of division into similar to each other segments. The medulla contains its own apparatus providing local simple and complex unconditional reflexes and pathways that convey impulses from the spinal cord and barrel to the interstitial and a large brain and back to the motor nuclei stem and spinal cord.
The staff of the medulla oblongata are the cells and nuclei reticular formation (see the Reticular formation), similar messagestream inserted the neurons of the spinal cord, as well as primary motor kernel receiving pulses from the primary receptor cells outside the Central nervous system. In the medulla contains the most important reflex centers - breathing, blood circulation, exchange, functioning under control and regulating influence the upstream centers of interstitial brain and cerebral cortex. On the ventral surface of the medulla oblongata in the middle of the line is the median front furrow, which is a continuation of the same furrows of the spinal cord. It ends on the border with bridge blind hole. On both sides of the middle of the front furrow are powerful beams reaching a longitudinal fibers of the pyramid of the medulla oblongata. Outside on each side of their restricts lateral front furrow, which is also a continuation of the corresponding grooves of the spinal cord.
From this furrows go roots hypoglossal nerve. Further outwards is located oval education - Oliva (oliva), and outwards from the olives from the rear side of the furrow roots go wandering, language-glotocnogo nerves and upper roots incremental nerve. Above is a gray mound, representing the surface downward root of the trigeminal nerve, the core of which is a gelatinous substance. Posterior to the rear side of the furrow is located in the rear pillar, the thicker in the field of medulla oblongata in comparison with the spinal cord due to the appearance of nuclei gentle and wedge-shaped beams, forming the corresponding elevation - Mons (tuberculum nuclei gracilis et tuberculum nuclei cuneati). Anterior at the level of olives is located cord fibers heading in the cerebellum-the lower leg of the cerebellum.
The diamond-shaped hole, the bottom IV heart, only in its lower part belongs to the medulla. Of primary nuclei P. M. then just posterior to lie kernel hypoglossal nerve, located near the midline. Outwards from the kernel hypoglossal nerve is back nucleus of the vagus and language-glotocnogo nerves (nucleus dorsalis nervi vagi)and outwards from it a bundle of fibers, surrounded by gray matter - single beam (tractus solitarius). The third nucleus of the vagus and language-glotocnogo nerves - nucleus ambiguus - lies in the depth of tyres of the trunk. The external angle of the diamond-shaped holes occupy the core of the auditory nerve. Cochlear part of the auditory nerve correspond to two cores: ventral nucleus cochlearis ventralis), located on the lower surface of the bottom of the leg of a cerebellum, and the dorsal nucleus cochlearis dorsalis, s. tuberculum acusticum) - on posterolateral the surface of the bottom of the leg of a cerebellum. Large territory is occupied kernels vestibular portion of the auditory nerve. This includes four core: medial, or triangular (nucleus vestibularis medialis), the core of Bekhterev (nucleus vestibularis superior), the core of Daters (nucleus vestibularis lateralis) and the core of the downward beam vestibular nerve nucleus vestibularis inferior). In large cages core Daters originates Vestibulo-spinal tract (tractus vestibulospinalis), which goes into the spinal cord and ends in the cells of the anterior horns. In Oliva originates Olivo-spinal beam. Rubro-spinal tract, beam Manakova (tractus rubrospinalis), only takes place in the lid of the barrel, heading from the cells of the red core of the middle brain to the cells of the front horns spinal cord. The most important of downstream systems pyramid is the path that transmits impulses from the zone of motor analyzer of a bark of the big hemispheres (the forward Central gyrus) to the motor cells of the anterior horns of the spinal cord. The bottom-up systems are the most important beams of the rear pillars of the spinal cord, Spino-thalamic and front and rear cerebellar beams. In kernels gentle and wedge-shaped beams over the first neurons system, conducting proprioceptive sensitivity. Starting from these cores fiber (neurons of the second order) mainly goes down, surrounding circular arcs of the Central gray matter within the interior arched fibers (fibrae arcuatae internae), perekrashivat the middle line, and then take the upward direction, forming the middle loop (lemniscus medialis). A smaller portion of the fiber cores gentle and wedge-shaped beam is sent to the cerebellum, the part of the lower leg of a cerebellum. Spino-thalamic only the way passes through the medulla, rising to the optic hill. Front cerebellar path goes through the diamond-shaped brain, going to the middle brain, and goes back to the upper crust of the cerebellar vermis in the lower part of the leg of a cerebellum.
Fiber from dorsal cochlear nucleus auditory nerve are drawn in a lateral direction across the bottom of the diamond-shaped holes, perekrashivat (imperfectly) the middle line and take the upward direction, forming lateral loop (lemniscus lateralis). Fiber from ventral cochlear nucleus auditory nerve are in an upward direction in the back part of the bridge, situated on the border between the base and lid, and cross the middle line as fiber trapezoidal body (corpus trapezoideum). These fibers end up at the top of Olivet, in the nucleus of the side hinges, and in cells, located between the fibers of a trapezoidal body. From here you can start neurons of the third order, then incoming part of the side hinges (see the Auditory nerve).