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Thalamus, metatamus and epithalamus
Last reviewed: 18.10.2021
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The thalamus (thalamus dorsalis; syn: posterior thalamus, visual hillock) - a pair formation, having a shape close to ovoid, located on both sides of the third ventricle. In the anterior part, the thalamus narrows and ends with the anterior tubercle (tuberculum anterius thalami). The posterior end is thickened and called a pillow (pulvinar).
Only two surfaces of the thalamus are free: medial, facing towards the third ventricle and forming its lateral wall, and the upper one, which participates in the formation of the bottom of the central part of the lateral ventricle.
The upper surface is separated from the medial white thin stria of the thalamus (stria medullaris thalamica). The medial surfaces of the posterior thalamus, right and left, are interconnected by interthalamic adhesion (adhesio interthalamica). The lateral surface of the thalamus is attached to the inner capsule. The thalamus borders on the lining of the midbrain.
The thalamus consists of a gray matter in which separate clusters of nerve cells are distinguished - the nuclei of the thalamus. These clusters are separated by thin interlayers of white matter. Currently, there are up to 40 cores, which perform various functions. The main nuclei of the thalamus are the anterior (nuclei anteriores), medial (nuclei mediates) and posterior (nuclei posteriores). With the nerve cells of the thalamus, the processes of nerve cells of the second (conductor) neurons of all sensitive pathways come into contact (except for the olfactory, taste and auditory). In this regard, the thalamus is practically a subcortical sensory center. Some of the processes of the thalamus neurons are directed to the nuclei of the striatum of the terminal brain (in this connection, the thalamus is considered to be the sensitive center of the extrapyramidal system), and part is the thalamocortical fascicles (fasciculi thalamocorticales) to the cerebral cortex.
Under the thalamus is located the so-called subthalamic region (regio subtalamica - BNA), which extends downward into the tire of the brain stem. This is a small area of the brain substance, separated from the thalamus from the side of the third ventricle by the hypothalamic furrow. The subthalamic region of the midbrain continues and the red nucleus and black matter of the midbrain terminate in it. On the side of the black substance is placed a subthalamic nucleus (nucleus subthaldmicus, lyus body).
Metatalamus (metathalamus; catalamic region) is represented by paired lateral and medial geniculate bodies - paired formations. These are oblong-oval bodies that connect with the mounds of the roof of the midbrain with the help of handles of the upper and lower hills. The lateral geniculate body (corpus geniculatum laterale) is located near the lower lateral surface of the thalamus, on the side of the pillow. It can be easily detected by following the course of the optic tract, the fibers of which are directed to the lateral geniculate body.
Several to the inside and back of the cranked lateral body, under the pillow, is a pair of medial geniculate corpus (corpus geniculatum mediale), on the cells of the nucleus which terminate the fibers of the lateral (auditory) loop. Paired lateral elbows with the upper hills of the midbrain are subcortical centers of vision. The medial geniculate bodies and the lower hills of the midbrain form the subcortical centers of hearing.
Epithalamus (epithalamus; subthalamic region) includes the pineal body, which by means of leashes (habenulae) connects to the medial surfaces of the right and left thalamuses. At the junction of the leashes in the thalamus there are triangular extensions - triangles of leashes (trigonum habenulae). The front sections of the leads before entering the pineal body form a soldering of the leashes (comissura habenularum). In front and below the pineal body is a bundle of transversely extending fibers - the epithelamic adhesion (commissura epithalamica). Between the epithelial adhesion and the soldering of leashes to the anteroposterior part of the pineal body, into its base, a shallow blind pocket - a pineal groove - is inserted.