The brain is the most complex organ in the structure of living organisms. Although a lot of books and textbooks have been written about the brain, there are still a lot of incompletely studied functions and sections. In this article we will try to explain in simple terms how the pyramids of the medulla oblongata are arranged, what the medulla oblongata itself is, and what functions of a living organism it is responsible for.
Medulla oblongata
The medulla oblongata (PM) appears in the higher chordate (vertebral) animals as a department of regulation of balance and hearing. It developed along with the gill apparatus, which is related to blood circulation and respiration. The medulla oblongata were the first to receive the simplest chordates (lancelet, fish and amphibians). Pyramids of the medulla oblongata appear in higher vertebrates. The cerebral cortex in humans is well developed, and the pyramids serve to connect parts of the brain with the new cortex. The medulla oblongata develops from the posterior cerebral bladder. From the brain bubbles, the remaining parts of the brain also develop.
The structure of the medulla oblongata in humans
The medulla oblongata is located in the posterior lower part of the head between the bridge and the spinal cord. PM is an extension of the spinal cord, so their structures are very similar. In shape, it resembles a truncated cone 25-30 mm long, squeezed in the posterior sections and rounded in the anterior ones. The dimensions of the medulla oblongata are relatively small: along it reaches 12-15 mm, across 10-12 mm. Its weight is 6-7 grams. A small transverse fissure, called the bulbar-bridge furrow, separates PM from the brain bridge. The lower boundary of PM is the lower edge of the intersection of the pyramids of the medulla oblongata. The medulla oblongata have ventral (anterior), dorsal (posterior) and lateral (lateral) surfaces. The furrows in them are extensions of the corresponding furrows of the spinal cord. Along the middle of the ventral surface of the PM passes the median gap, on the sides of which there are pyramids.
The structure of the pyramids
Pyramids PM are longitudinal strands (ridges), composed of fibers of partially intersecting pyramidal paths. Then the fibers pass into the lateral cord of the spinal cord and form the lateral cortical-spinal path. The remaining bundles of fibers line the anterior cortical and spinal path. Both of these paths are part of the pyramidal system. The pyramidal system is the connection of the parts of the spinal cord responsible for movement with the motor centers of the cerebral cortex through the pyramids of the medulla oblongata. The pyramidal pathway of an adult occupies about 30% of the spinal cord in cross section.
Olive structure
Olives of the medulla oblongata are located outside the pyramids and are an oblong-rounded elevation, separated from the pyramid by the anterolateral groove, which is a continuation of the same groove of the spinal cord. The pyramids and olives of the medulla oblongata are connected by external arcuate fibers that start from the lower edge of the olive. In addition to the nerve fibers in the olives, there is a gray matter, which forms an olive cloak and an olive lower core. In addition to the bottom, the olive contains a radial accessory olive kernel and a back accessory olive kernel, which are smaller than the main kernel.
Medulla oblongata
The medulla oblongata is responsible for a huge number of vital functions. Its damage is very dangerous and in almost 100% of cases leads to death. Under his control, such complex reflexes as swallowing, chewing, sucking, coughing, sneezing, vomiting, salivation and lacrimation. PM is also involved in the regulation of blood circulation and respiration. In addition to vital reflexes, the medulla oblongata coordinates sensory functions. PM receives impulses from receptors of such parts of the body as the respiratory tract, mucous membranes, facial skin, internal organs and the hearing aid. Due to the fact that the impulses reach the medulla oblongata, the corresponding reflexes are formed: blinking, facial expressions, secretion of the stomach, pancreas and salivary glands.
The functions of the pyramids of the medulla oblongata
As mentioned earlier, the PM pyramids act as intermediaries between the spinal cord and the new cerebral cortex. Pyramids are part of the pyramidal system, which performs many important functions. Pyramids include only the pyramidal path, and therefore are considered an isolated system. During the experiments, scientists found that with mechanical damage to the pyramids in experimental dogs and cats, minor impairments of motor functions were observed, which disappeared after a few days. As a result of many years of research, scientists have found that the pyramids of the medulla oblongata contain bundles of nerve fibers, which are a link in the regulation of the activity of spinal motor neurons. Spinal - related to the spinal cord; motor neurons are large motor nerve cells of the spinal cord. Provide muscle coordination and support muscle tone.
Pathology of the pyramidal system
Violations of the pyramidal system are observed with organic lesions of the central nervous system. Lesions of Ps work also often accompany circulatory disorders in the spinal cord and brain (strokes, crises). In cerebral crises, the signs of damage to the pyramidal system are transient in nature and pass quickly enough. Pyramidal insufficiency often accompanies tumors of the brain or spinal cord, traumatic, infectious and intoxication lesions of the central nervous system.
Symptoms
Disturbances in the functioning of the pyramidal system are movement disorders, paralysis and paresis, an increase in muscle tone in the spastic type, high tendon reflexes and a decrease in some skin reflexes. To detect a violation of the functioning of the pyramids of the medulla oblongata, the Juster test is used - when pricked with a pin into the area of the elevation of the thumb (tenar), the thumb bends towards the index finger, while the other fingers are bent, and the hand and forearm are bent in the back. Often, a symptom of a folding knife indicates the defeat of the pyramidal system. This symptom is characterized by sudden resistance to the limb with passive flexion of the elbow or knee joint. Resistance passes quickly during exposure, and the limb easily bends to the end. The clinical manifestations of Ps lesion are very diverse. Most often hemiplegia can be observed. Left-sided or right-sided hemiplegia is characterized by spastic paralysis of half the body, opposite the focus of the pathology. Moreover, the arm is paralyzed more than the leg.