The brain is the most complex organ of living organisms. Although many books and textbooks have been written about the brain, there are still many functions and areas that have not been fully explored. In this article, we will try to explain in simple terms how the pyramids of the medulla oblongata are arranged, what the medulla itself is and what functions it is responsible for in a living organism.
Evolution of the medulla oblongata
The medulla oblongata (M) appears in higher chordates (vertebrates) as a department for regulating balance and hearing. It developed along with the gill apparatus, which is related to blood circulation and respiration. The medulla oblongata was the first to receive the simplest chordates (lancelets, 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. OblongThe embryonic brain develops from the posterior medulla. The rest of the brain also develops from the cerebral vesicles.
The structure of the human medulla oblongata
The medulla oblongata is located at the back of the lower part of the head between the pons and the spinal cord. The PM is a continuation of the spinal cord, so their structures are very similar. In shape, it resembles a truncated cone 25–30 mm long, compressed in the posterior sections and rounded in the anterior. The dimensions of the medulla oblongata are relatively small: along it reaches 12-15 mm, across 10-12 mm. Its mass is 6-7 grams. From the bridge of the brain, the Pm is separated by a small transverse fissure, called the bulbar-pontine groove. The lower border of the Pm is considered to be the lower edge of the decussation of the pyramids of the medulla oblongata. The medulla oblongata has ventral (anterior), dorsal (posterior), and lateral (lateral) surfaces. The furrows located in them are continuations of the corresponding furrows of the spinal cord. A median fissure runs along the middle of the ventral surface of the PM, with pyramids on the sides.
The structure of the pyramids
Pyramids Pm are longitudinal strands (rollers), consist of fibers of partially intersecting pyramidal pathways. Further, the fibers pass into the lateral funiculus of the spinal cord and form the lateral cortical-spinal cord. The remaining bundles of fibers line up the anterior cortical-spinal tract. 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 withmotor centers of the cerebral cortex through the pyramids of the medulla oblongata. The adult pyramidal tract occupies about 30% of the cross-sectional area of the spinal cord.
The structure of olives
Olives of the medulla oblongata are outside the pyramids and represent an oblong-rounded elevation, separated from the pyramid by the anterolateral groove, which is a continuation of the same furrow of the spinal cord. Also, the pyramids and olives of the medulla oblongata connect the outer arcuate fibers that start from the lower edge of the olive. In addition to the nerve fibers found in the olives, there is a gray matter that forms the olive mantle and the olive lower core. In addition to the lower, the olive contains a radial additional olive core and a rear additional olive core, which are smaller in size than the main core.
Functions of the 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 are 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. The PM receives impulses from receptors in 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, they formreflexes corresponding to them: blinking, facial expressions, secretion of gastric, pancreatic and salivary glands.
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 pyramid system, which performs many important functions. Pyramids include only the pyramidal pathway and are therefore considered an isolated system. In the course of the experiments, scientists found that with mechanical damage to the pyramids in experimental dogs and cats, minor impairments in 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 in the spinal cord. Provides muscle coordination and support for muscle tone.
Pathologies of the pyramidal system
Disorders of the pyramidal system are observed in organic lesions of the central nervous system. Damage to the work of Ps is also often accompanied by circulatory disorders in the spinal cord and brain (strokes, crises). In cerebral crises, the signs of damage to the pyramidal system are transient and disappear fairly quickly. Pyramidal insufficiency often accompanies tumors of the brain or spinal cord, traumatic, infectious and intoxication lesions of the central nervous system.system.
Symptoms
Characteristic for disorders of the pyramidal system are movement disorders, paralysis and paresis, increased spastic muscle tone, high tendon reflexes and a decrease in some skin reflexes. To detect a malfunction of the pyramids of the medulla oblongata, the Juster test is used - when a pin is pricked into the area of the eminence of the thumb (tenar), the thumb is bent towards the index finger, the remaining fingers are unbent at the same time, and the hand and forearm are bent in the back parts. Often, a jackknife symptom indicates a lesion of the pyramidal system. This symptom is characterized by sudden resistance of the limb during passive flexion of the elbow or knee joint. Resistance during exposure quickly passes, and the limb easily bends to the end. The clinical manifestations of Ps lesions are very diverse. The most common is hemiplegia. Left-sided or right-sided hemiplegia is characterized by spastic paralysis of the half of the body opposite to the focus of pathology. Moreover, the arm is more paralyzed than the leg.
