Hippocampus: anatomy and functions (2023)

Anatomy

HeHippocampusIt is an elongated convex structure that projects from the floor and medial wall of theTemporary Hornof the lateral ventricle. It is about 5 cm long and widest in its anterior extent, where it flexes towards the medial aspect of the brain.correct hippocampusAlso calling 'a warning horn', meaning the horn of the ancient Egyptian god Amun.

The hippocampus extends anteriorly from the amygdala and then narrows as it runs posteriorly. Some authors divide its surface into three parts: head, body and tail.Kopfthe hippocampus contains several grooves that resemble a foot and is therefore known as thepes hippocampus(L. pes, "hit").

The ventricular surface of the hippocampus is calledreservoir. The alveolus is a thin layer of white matter formed by the axons of the pyramidal cells of the hippocampus. It is covered by the ependymal cell layer. Alveolar fibers converge at the medial border of the hippocampus to formRand des Hippocampuswhich in turn gives rise to the fornix.

When viewed in cross-section (coronal) section, the hippocampus is divided into four designated zonesCA1-CA3(CA - Cornu ammonis). The initial division also included the fieldCA4, but today this field is considered part of the dentate gyrus.

HeCA1field, also known asSommers Sector, contains the pyramidal cells closest to the subiculum, while the other two fields CA2 and CA3 are closest to the surface. A special feature ofCA3Of note, the collaterals of the axonal processes that extend from the CA3 pyramidal cells are known as recurrent orSchaffer collateral, and these fibers actually project back into the CA1 field.

Internal structure

The inner hippocampus consists ofArchikortex.Note that the archcortex has fewer cortical layers than bothNeokortex(which has six layers) and thepaleocorteza(who has four or five).

The archcortex of the hippocampus consists mainly ofpyramidal cells. Pyramidal cells, like all cells, have afferent processes (dendrites) and efferent processes (axon). It should be noted that the dendrites of a pyramidal cell extend from both the apex and the base. The basicdendritesthey extend toward the surface of the lateral ventricles; while the apical dendrites extend away from the lateral ventricles and towards the dentate gyrus.

Heaxonpyramidal cells take information received from the hippocampus and send it to other brain structures; These efferent processes extend from the pyramidal cell body and travel through a structure called the Elreservoirfibrous cape adjacent to the inferior horn of the lateral ventricle and then enters the entorhinal cortex or theborder area-fornix.

The hippocampal archcortex consists of four main layers:

• Helacunar molecular layerIt is the deepest layer of the hippocampus archcortex. This layer is mainly composed of interneurons.
• Heradiate layerIt is formed mainly by the dendrites of pyramidal cells and stellate cells.
• Hepyramid layerIt is the thickest and most important layer of the hippocampus. It consists of densely packed pyramidal neurons. The pyramidal layer merges with the inner pyramidal layer of the neocortex.
• Heeast headIt is the most superficial layer of the hippocampus, located just below the alveolus. It consists primarily of basket cell interneurons and shares many structural features with the deeper layer of the neocortex.

Note that some anatomy textbooks use an older classification of the hippocampus layer, which divides the structure of the hippocampus into three layers: molecular, pyramidal, and polymorphic.

a cogwheel

Hea cogwheelIt is a band of cortex located between the superior aspect of the parahippocampal gyrus and
the hippocampus fimbria. The dentate gyrus gets its name from its tooth-like configuration. This configuration is created by numerous blood vessels piercing the ventricular surface of the hippocampus and the dentate gyrus.

Like the hippocampus, theirregular giroit also has several layers; but unlike the hippocampus, whose main cell is the pyramidal cell, the main cell of the dentate gyrus is thegranule she was whole. The axons of granule cells are calledjelly fibras, and synapse with pyramidal cells in theCA3hippocampal field.

The three layers that make up the dentate gyrus are (superficial to deep):

• Hemolecular layerConsists mainly of nerve cell bodies and granules
  cellular dendrites;
• Hegranular middle layercomposed of granular cells, the main cells of the dentate gyrus;
• Hemultifaceted layerconsists mainly of interneurons.

subicular cortex

Hesubicular Kortexor just thea small roomIt is a transitional area between the hippocampus and the entorhinal cortex. The main distinguishing feature between the hippocampus and the subicular cortex is that thepyramidal she was whole capain the subicular cortex it is significantly thicker than in the hippocampus.

The most importantFunctionof the subiculum is to transmit information from the pyramidal cells of the hippocampus to the amylary nuclei of the hypothalamus and the anterior nuclei of the thalamus.

Do you feel a little confused? Why don't you try testing your understanding with a few?exam questions?You can use them to learn hippocampus anatomy from scratch or to identify gaps in your knowledge.

Hippocampal connections: pros and cons!

functions

Despite being a fairly small structure in the brain, size can be deceiving! The hippocampus performs a number of crucial functions, including the regulation of emotions, motivation, hormonal activity, autonomic activity and memory formation.

The most well-known function of the hippocampus is its role inLearnYStore. Although the exact mechanisms remain somewhat mysterious, it is believed that the hippocampus receives and consolidates information, allowing the formation of long-term memories in a process known asLong term potentiation(LTP). It also plays a role in spatial memory, allowing us to keep track of where things are and how they relate to one another. as such, it is fundamental in the formation of cognitive maps.

There are numerous reports linking human tumors, lesions, and epileptogenic activity in the hippocampus with aggressive responses ranging from mild hostility to explosive acts of violence. The role of the hippocampus in mediationAssaultYvayait seems to depend on the region of the stimulated structure: activation of the temporal pole, the region closest to the amygdala, stimulates predatory or fighting behavior; while activation of the region closest to the septal pole suppresses these pulses.

Given the numerous synaptic connections between the hypothalamus and hippocampus, it is not surprising that the hippocampus is also involved.hormones regulationand contributes to severalendocrine functions. The ventral aspects of the hippocampus were found to harbor dense regionsestradiol-Concentration of neurons, as well as high concentrations ofcorticosteronawhich inhibits these estradiol-concentrating neurons.

It has been postulated that the hippocampus may be selectively sensitive to different levels of hormones, which play a role in childbirth.feedback to thehypophysisthrough their hypothalamic connections. This is believed to occur indirectly via a synaptic relay within the septal area, as well as directly via a pathway calledmedial cortico-hypothalamic treatment. The medial corticohypothalamic tract arises near the temporal pole of the hippocampus and projects to the ventromedial hypothalamus; terminates between the suprachiasmatic and arcuate nuclei in a region that contains hypophysiotrophic hormones that mediate anterior pituitary functions.