The cerebral cortex is anatomically represented by a plate of gray matter lining the outer part of the hemispheres. Its folded structure is due to the large number of convolutions separated by furrows. Moreover, most of the bark is located deep in the furrows, and a smaller part is located on their surface. In the hemisphere, a convex (external) and internal surface, as well as the base, are distinguished. On the external surface, the parietal lobe is separated from the frontal with the help of a powerful "Roland" furrow. Below it is the "Sylvian" groove, with which the temporal lobe is separated from the frontal and parietal. The parietooccipital furrow separates the occipital lobe.
The microscopic structure of the cortex includes a number of fibrous and cellular layers and refers to a six-layer type of structure.
In this case, the following layers are determined:
- external granular;
- internal granular;
- molecular;
- polymorphic cells;
- large pyramidal cells;
- medium and small pyramidal cells.
The structure and functions of the medulla oblongata, the consequences of its defeat
Its length is about twenty-eight millimeters, and the width, gradually increasing, reaches twenty-four millimeters. The medulla oblongata continues in the cranial cavity to the spinal cord, through the central spinal canal. In its substance, there is the presence of separate clusters of gray matter, which form the nuclei of the nerves of the skull. In the formation of white matter involved fibers of the pathways. The medulla oblongata contains nuclei from which the roots of important cranial nerves (vagus, sublingual, glossopharyngeal, accessory) go out. In addition, the nuclei are involved in reflex processes such as chewing, swallowing, sucking, sneezing, vomiting, and the separation of digestive juice. The formation of nuclei in humans occurs during the development period inside the womb. The medulla oblongata (along with the bridge) has a weight of about eight grams. Ripening lasts an average of up to seven years.
Centripetal and centrifugal impulses are conducted along paths passing through the medulla oblongata. One of the most important paths is the pyramidal path. It connects the motor region in the cerebral cortex and the motor cells of the anterior spinal horns. At the border of the dorsal and oblong divisions, a cross is observed in the pyramidal ducts. This explains the functional disturbances in the functioning of certain parts of the brain when they are damaged. So, for example, a lesion in the pyramidal bundle above the intersection causes hemiplegia on the side of the body opposite to the focus. With simultaneous damage to the cranial nerves, functional disorders occur on the same side of the body.
The “cerebellopontine angle” performs a connecting function. Located in the posterior fossa of the skull, it is the junction of the bridge, cerebellum and medulla oblongata. When tumors occur in this place, compression of the nearest sections of these departments occurs.
The medulla are located in the medulla oblongata, which attaches particular importance to this department in the central nervous system. Here are the cardiovascular and respiratory centers. That is why damage (even minor) and especially the removal of the medulla oblongata leads to death, due to respiratory arrest and termination of the cardiovascular system.
Damage to the pyramidal pathway can lead to various consequences. It all depends on the size of the injury and the time that has passed since its inception. In many cases, such injuries cause severe paralysis in a person for one or two weeks.