The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections.
Its function includes relaying sensation, special sense and motor signals to the cerebral cortex, along with the regulation of consciousness, sleep and alertness.
The thalamus surrounds the third ventricle. It is the main product of the embryonic diencephalon.
The thalamus is the largest structure in the diencephalon,
the part of the brain situated between the midbrain (mesencephalon) and
Anatomically, the thalamus is perched on top
of the brainstem, near the center of the brain, in a position to send
nerve fibers out to the cerebral cortex in all directions.
diencephalon includes also the dorsally located epithalamus (essentially
the habenula and annexes) and the perithalamus (prethalamus formerly
described as ventral thalamus) containing the zona incerta and the
"reticulate nucleus" (not the reticular, term of confusion).
their different ontogenetic origins, the epithalamus and the
perithalamus are formally distinguished from the thalamus proper.
In humans, the two halves of the thalamus are prominent
bulb-shaped masses, about 5.7 cm in length, located obliquely (about
30°) and symmetrically on each side of the third ventricle.
The thalamus comprises a system of lamellae (made up of myelinated
fibers) separating different thalamic subparts.
Other areas are defined
by distinct clusters of neurons, such as the periventricular gray, the
intralaminar elements, the "nucleus limitans", and others.
structures, different in structure from the major part of the thalamus,
have been grouped together into the ''allothalamus'' as opposed to the
''isothalamus''. This distinction simplifies the global description of
The thalamus derives its blood supply from a number of arteries
including polar and paramedian arteries, inferolateral
(thalamogeniculate) arteries, and posterior (medial and lateral)
choroidal arteries. These are all branches of the posterior cerebral
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