Epitalamus: What is it? Functions, Anatomy and Structure

It is a diencephalic part located on the thalamus.

The diencephalon is a part of the forebrain that also contains the thalamus , the hypothalamus and the pituitary gland.

The epithalamus includes the habenula and its interconnected fibers, the habenular commissure, the medullary stria and the pineal gland.

Functions

The function of the epithalamus is to connect the limbic system to other parts of the brain. Some functions of its components include the secretion of melatonin and the secretion of hormones from the pituitary gland by the pineal gland (involved in circadian rhythms) and the regulation of motor pathways and emotions.

Anatomy of the epithalamus

The epithalamus comprises the habenular trine, the pineal gland and the habenular commissure. It is connected to the limbic system and the basal ganglia.

Species that possess a parapineal photoreceptor organ show asymmetry in the epithelium in the habenula, to the left (dorsal).

Very close to the medullary striae, which are the nerve fibers that establish connections with other regions of the brain, there are two large structures, which are the most relevant and known of the epitalamo:

Epiphysis or pineal gland:

The epithelium is represented mainly by the pineal gland, which is in the posterior midline and dorsal to the third ventricle.

This gland synthesizes melatonin and enzymes sensitive to daylight. The rhythmic changes in the activity of the pineal gland in response to daylight suggest that the gland functions like a biological clock.

The pineal gland produces melatonin, a hormone derived from serotonin that modulates sleep patterns in circadian and seasonal cycles.

The shape of the gland resembles a pine cone, hence its name. The pineal gland is located in the epithelium, near the center of the brain, between the two hemispheres, tucked into a groove where the two halves of the thalamus meet.

The pineal gland is a brain structure of the midline that is not paired. It takes its name from its pine cone shape. The epiphysis in humans is reddish gray and about the size of a grain of rice.

The pineal gland, also called the pineal body, is part of the epithalamus and is found between the thalamic bodies located laterally and behind the habenular commissure.

It is located in the quadrigeminal cistern near the corrige quadrigemina. It is also located behind the third ventricle and is bathed in cerebrospinal fluid that is delivered through a small pineal recess of the third ventricle that projects to the stem of the gland.

Habenular nuclei:

Also called habénula. It is located next to the pineal gland and makes possible the communication between the limbic system and the reticular formation.

The habenula, unlike the pineal gland, has no endocrine functions. It acts as a regulator of the key neurotransmitters of the central nervous system, which connects the forebrain and mesencephalon within the epithelium.

The habenular nuclei comprise a small group of nuclei that are part of the diencephalon epithelium, and is located just above the thalamus and is divided into two asymmetric halves: the medial habenula (MHb) and the lateral habenula (LHb).

These nuclei have the hypothesis of being involved in the regulation of monamins, such as dopamine and serotonin.

The medial habenula receives connections from the posterior film wall and Broca’s diagonal band; The lateral habenula receives afferents from latera hypothalamus, nucleus accumbens, internal pale balloon, ventral pallidum and Broca diagonal band.

Together, this complexly interconnected region is part of the dorsal diencephalic conduction system, responsible for transmitting information from the limbic system to the mesencephalon, the rhombencephalon and the medial forebrain.

Habenula nuclear divisions:

  • Lateral habenular nucleus.
  • Medial habenular nucleus.
  • The pineal gland is attached to the brain in this region.

The nerve impulses of the habenular nuclei are transmitted to the septal nuclei through the medullary stria, which is found on the medial surface of the thalamus.