Hippocampus: anatomy and functions (2023)

Anatomy

OHippocampusis an elongated convex structure projecting 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 called 'A warning horn', meaning the horn of the ancient Egyptian god Amon.

The hippocampus extends anteriorly from the amygdala and tapers as it runs posteriorly. Some authors divide its surface into three parts: head, body and tail.Kopfthe hippocampus contains several grooves that resemble a paw and is therefore called thePes Hippocampus(L. pes, "pe").

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. Fibers from the alveolus 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) the hippocampus is divided into four designated zonesCA1-CA3(CA - Cornu ammonis). The initial division also included the fieldCA4, but nowadays this field is considered part of the dentate gyrus.

OCA1field, 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 guarantee, 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 thePaleocórtex(which 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.

Oaxonpyramidal cells receive 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 theReservoirfibrous layer adjacent to the inferior horn of the lateral ventricle and then enters the entorhinal cortex or theedge area-fornix.

The hippocampal archcortex consists of four main layers:

• Olacunar-molecular layerIt is the deepest layer of the hippocampal archcortex. This layer consists mainly of interneurons.
• Oradiate layerconsists mainly of the dendrites of pyramidal cells and stellate cells.
• Opyramid 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.
• Oeastern layerIt is the most superficial layer of the hippocampus, which is 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 hippocampal layer that divides the structure of the hippocampus into three layers: molecular, pyramidal, and polymorphic.

a sprocket

Oa sprocketis a band of cortex located between the superior aspect of the parahippocampal gyrus and
the fimbria of the hippocampus. 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 dentate gyrus.

Like the hippocampus, thejagged giroit is also multilayer; but unlike the hippocampus, whose primary cell is the pyramidal cell, the primary cell of the dentate gyrus is thegranule cell. The axons of granule cells are calledjelly fibras, and they synapse with the pyramidal cells in theCA3hippocampus field.

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

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

subicular cortex

Osubicular 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 cell layerin 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.

Feeling a little confused? Why not try testing your understanding with a few?quiz questions?You can use them to learn hippocampus anatomy from scratch or to identify gaps in your knowledge.

Hippocampus connections: pros and cons!

functions

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

The most well-known function of the hippocampus is its role inLearnEStore. 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 instrumental in forming cognitive maps.

There are numerous reports linking human tumors, lesions, and epileptogenic activity in the hippocampus to aggressive responses ranging from mild hostility to explosive acts of violence. The role of the hippocampus in mediationAggressionEwhatit seems to be dependent 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 the deliveryfeedback to thehypophysisthrough their hypothalamic connections. This is thought to occur indirectly via a synaptic relay within the septal area, as well as directly via a pathway calledCortico-medial hypothalamus 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 containing hypophysiotrophic hormones that mediate anterior pituitary functions.