from The American Heritage® Dictionary of the English Language, 4th Edition
- n. See diencephalon.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The segment of the brain next in front of the midbrain, including the thalami, pineal gland, and pituitary body.
from the GNU version of the Collaborative International Dictionary of English
- n. The segment of the brain next in front of the midbrain, including the thalami, pineal gland, and pituitary body; the diencephalon; the interbrain.
from The Century Dictionary and Cyclopedia
- n. The parts of the brain about the third ventricle developed from the hinder part of the first primary cerebral vesicle, including the thalami, the optic tracts and chiasma, the infundibulum and cerebral part of the pituitary body, the corpora albicantia, the conarium, the ependymal part of the velum interpositum, a lamina cinerea, and other structures. Also called diencephalon, interbrain, 'tween-brain. See cuts under Elasmobranchii, encephalon, Rana, Petromyzontidæ, and cerebral.
The original fore-brain is often called the thalamencephalon, the hemisphere, the prosencephalon, the olfactory lobes, the rhinencephalon.
The longitudinal part of this sulcus expands superiorly to form a slight depression which supports the pineal body, a cone-like structure which projects backward from the thalamencephalon and partly obscures the superior colliculi.
The mid-brain or mesencephalon (Fig. 681) is the short, constricted portion which connects the pons and cerebellum with the thalamencephalon and cerebral hemispheres.
The thalamencephalon comprises: (1) the thalamus; (2) the metathalamus or corpora geniculata; and (3) the epithalamus, consisting of the trigonum habenulæ, the pineal body, and the posterior commissure.
The diencephalon comprises: (1) the thalamencephalon; (2) the pars mamillaris hypothalami; and (3) the posterior part of the third ventricle.
The cerebral hemispheres are not convoluted, and, looked at from the dorsal aspect, do not hide the thalamencephalon and mid-brain.
The fore-brain consists of a thalamencephalon (th.c. and 1), which is exposed in the dorsal view of the brain, and which has no middle commissure.
The cerebral hemispheres (c.h.) are not convoluted, do not extend back to cover parts behind them, as they do in the rabbit, and are not connected above the roof of the thalamencephalon by a corpus callosum.
Finally, we may note the pineal gland and the pituitary body, as remarkable appendages above and below the thalamencephalon.
[S.P.G.], stalk of the pineal gland. th., thalamencephalon.th. c., thalamencephalon.
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