Author:Roberto Grujicic MD•Accountant:Dimitrios Mytilinaios MD, PhD
Last Verified: December 05, 2022
Reading time: 18 minutes
OHippocampusit is a paired structure present in each temporal lobe of the brain. It takes its name from the Greek word forSeahorse, because it resembles this small upright swimming fish.
The hippocampus is part of a larger temporal lobe structure called the temporal lobe.formation of the hippocampus. The formation of the hippocampus extends from the amygdala forward to the splenium of the corpus callosum behind. The formation of the hippocampus is an important part of thelimbic systemand consists of three main parts:
- OHippocampus(also known ascorrect hippocampus or ammon's horn),
- Oa sprocket,
- Oa small room.
The elongated structures of the hippocampus lie along the long axis of theBrainand form the floor and part of the medial wall of the inferior horns of thelateral ventricle. The hippocampus has many functions, but is best known for its roleLearnEStore.
|To her||Molecular, pyramidal and polymorphic layers|
|Felder||CA1, CA2, CA3, CA4|
|afferent pathways||Entorhinal cortex, septal region, prefrontal cortex, anterior cingulate gyrus, premammary region, reticular formation|
|efferent pathways||Septal area (precommissural fornix), anterior thalamic nucleus, hypothalamic mammillary bodies (postcommissural fornix), entorhinal cortex, cingulate cortex, prefrontal cortex, contralateral hippocampus|
|functions||Learning, memory, aggression, anger, hormone regulation|
- Internal structure
- a sprocket
- subicular cortex
- Hippocampus connections: pros and cons!
- hippocampus input
- hippocampus output
- Clinical Relations
- epilepsia temporal
- rabies encephalitis
- Isquemia cerebral global
- alzheimer's dementia
- Korsakoff's Syndrome
+ show all
Synonym:formation of the hippocampus, proper hippocampus,Show more...
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.
Synonym:Horn of Ammons, Horn of Ammons Area 1,Show more...
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.
Hippocampus Schicht polymorph
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.
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
- Ogranular middle layercomposed of granular cells, the main cells of the dentate gyrus;
- Omultifaceted layerconsists mainly of interneurons.
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!
Oentorrinal Kortexit is an important source of two distinct sets of afferent fibers that provide information for the formation of the hippocampus. Osideways to drill Absentit originates from the lateral entorhinal cortex and extends to the molecular layer of the hippocampus. Omedial to drill Absentarises from the medial entorhinal cortex, extends through the white matter from the subicular cortex, and enters the alveoli of the hippocampus. Many of these fibers carry olfactory, visual, and auditory information to the hippocampus.
ODiagonal Banda von Brocait originates from the septal area and functions as part of a feedback loop to the hippocampus from the septal area. The other part of this feedback loop is thepräcomissuralfornix, which allows the septal area to receive feedback from the hippocampus.
The hippocampus also receives afferent input from theprefrontal cortex,anterior cingulate gyrus, Epre-mamillaryRegionof the brain, as well as monoamine neuronal projections from thenet-like structure I amtronco cerebral(particularly the locus coeruleus, raphe nucleus, and ventral tegmental area). The monoamine pathway, in particular, plays an essential role in mood regulation.
Because of these connections, the hippocampal formation is able to respond to changes in activity in the cortex and brainstem and transmit this information to the brain.hypothalamus, adding an emotional or visceral quality to these changes in brain activity.
The efferent fibers of the hippocampal formation, which send signals from the hippocampus to other parts of the brain, come from thepyramidal cellsthe hippocampus and the subicular cortex. fibers of theAmygdala, located in front of the hippocampus, also move widely in tandem with hippocampal fibers. These fiber bundles, originating in the hippocampus and amygdala, pass posterodorsally along the body of the lateral ventricle around the posterior part of the ventricle.thalamus, and then anteriorly along the inferior horn of the lateral ventricle.
The bundle of fibers arising from the hippocampus is called thefornix; is just less thannumb body. The bundle of fibers arising from the amygdala is called the matrix.Stretch marknot end device, and runs parallel and ventromedially to the tail of the caudate nucleus. The fornix and stria terminalis fiber networks eventually terminate in different parts of the hypothalamus and septum.
Fibers from the fornix that travel rostrally to theanterior commissureare your namespräcomissuralfornix. These originate from both the hippocampus and the subicular cortex and terminate in the septal region. The fibers of the precommissural fornix are topographically organized: this means that fibers close to the anterior pole of the hippocampal formation project to the lateral surface of the lateral septal nucleus, while fibers close to the posterior part of the hippocampal formation project to more medial portions of the precommissural fornix. lateral septal nucleus.
The fibers of the fornix that run ventrally behind the anterior commissure are called thepostcommissuralfornix. These fibers originate from the subicular cortex and terminate in theanterior thalamic nucleusor in the mammary bodies of the hypothalamus. The postcommissural fornix innervates parts of themidbrain, including the anterior nucleus of the thalamus, the mamillary bodies, and parts of the medial hypothalamus.
neurons of thea small roomthey also send axons to the entorhinal cortex, the cingulate cortex, and regions of the prefrontal cortex. Oentorrinal Kortexsubsequently sends axons to the amygdala and parts of the temporal cortex. These interconnecting networks allow the hippocampus formation to send signals anywhere.cerebral cortex, including regions that receive and process different types of sensory information.
there is one tooacting Componentsof the fornix: The purpose of this part of the fornix is to connect the hippocampus on both sides of the brain. The axons that do this predominantly arise from the CA3-CA4 portions of the hippocampus and from the synapse in the contralateral hippocampus. It is believed that these binding fibers may provide the pathway for thisThe seizures spreadfrom its primary epileptogenic focus in one hippocampus to the contralateral hippocampus, eventually allowing a secondary epileptogenic focus to form in the contralateral hippocampus.
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.
Temporal lobe epilepsy is characterized by recurrent, unprovoked seizures originating in the temporal lobe, arguably the most epileptogenic region of the brain. These seizures can beconscious focal seizures(simple partial seizures that occur without loss of consciousness) andfocal impaired consciousness(complex partial seizures with loss of consciousness), although generalized seizures may also occur. OCA1 campoof the hippocampus, known as the summer sector, is particularly susceptible to the anoxia that can occur during temporal lobe epilepsy; this may be accompanied by excitement or aggression, anger, fear, paranoia and other emotional phenomena.
Rabies is a negative-sense, single-stranded, spherical RNA virus that is transmitted to humans by the bite of an infected animal (usually a dog, bat, or other mammal) and causes fatal encephalitis.brain inflammation). Once the victim has been inoculated with the virus through the bite, the virus ascends to the brain through the peripheral nerves. Initial symptoms are nonspecific, including headache, fever, and malaise. As the virus progresses, the victim experiences extremescentral nervous systemexcitabilityit manifests as hypersensitivity to pain, violent motor reactions, and convulsions. Make violent contractions of the throat musclesTo swallowdifficult and painful; Because of this, people with symptomatic rabies avoid drinking, even water, and are therefore called "hydrophobic." These spasms in the throat are also the cause of the characteristic foam at the mouth. Eventually meningismus occurs, followed by flaccid paralysis; The alternation between mania and drowsiness leads to coma and eventually death from failure of the brain's respiratory center.
Pathognomonic histopathological findings in rabies are called round or oval eosinophilic cytoplasmic inclusionsNegri Body, which can be seen in thepyramidal neuronhippocampus and Purkinje cellscerebellum.
Isquemia cerebral global
Global cerebral ischemia (also known asdiffuse hypoxic/ischemic encephalopathy) is the result of a severe hypotensive episode. Among the cells of the central nervous system, neurons are the most susceptible to ischemia, although glial cells are also susceptible. Different regions of the brain are also more vulnerable than others: the pyramidal cells in theCA1 Regionof the hippocampus, Purkinje cells in thecerebellum, and pyramidal cells in the cortex are more susceptible to global ischemia and can be damaged even when the ischemic episode is of short duration.
The hippocampus, along with the entorhinal cortex and amygdala, is involved in the early course of Alzheimer's dementia and often shows severe atrophy in the later stages of the disease. In particular, the hippocampus is a site of significant formation for bothneuritic plates(Collections of dystrophic neurites around a central Aβ amyloid core) andneurofibrilar tangled(intracytoplasmic bundles of filaments containing hyperphosphorylated tau protein surrounding or even moving away from the nucleus of the neuron).granulovakuolar Degeneration(formation of small, clear cytoplasmic vacuoles, each containing an argyrophilic granule) are also seen in abundance in the hippocampus of Alzheimer's patients; ANDhirano Body(eosinophilic inclusion bodies composed mainly of actin filaments) can be seen particularly in the pyramidal cells of the hippocampus.
Korsakoff syndrome is a disorder in which damage to the hippocampus causes new memories (anterograde memory loss) and recall memories made before damage (retrograde memory loss). It is usually associated withThiamine (Vitamin B1)-Deficiency, often associated with chronic alcohol abuse and its toxic effects on neurons, especially those in the hippocampal formation and the Papez circuit (mamillary body, cingulate gyrus and anterior thalamic nucleus).
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