from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The anterior part of the embryonic hindbrain, which gives rise to the cerebellum and pons.
- n. The cerebellum and pons of the adult brain.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. the portion of the embryonic rhombencephalon from which the pons and cerebellum arise.
from the GNU version of the Collaborative International Dictionary of English
- n. The posterior part of the brain, including the medulla; the afterbrain. Sometimes abbreviated to meten.
from The Century Dictionary and Cyclopedia
- n. The afterbrain; the medulla oblongata as far as the pons Varolii: synonymous with myelencephalon of Huxleyand others, and macromyelon of Owen.
- n. The cerebellar segment of the brain, the chief parts of which are the cerebellum and pons Varolii. Huxley. See cuts under brain and encephalon.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. the part of the hindbrain that develops into the pons and the cerebellum
It is customary to divide the rest of the hind-brain into two parts, viz., an upper, called the metencephalon, and a lower, the myelencephalon.
The pons is developed from the ventro-lateral wall of the metencephalon by a process similar to that which has been described for the medulla oblongata.
The cerebellum is developed by a thickening of the roof, and the pons by a thickening in the floor and lateral walls of the metencephalon.
It consists of (a) the myelencephalon, comprising the medulla oblongata and the lower part of the fourth ventricle; (b) the metencephalon, consisting of the pons, cerebellum, and the intermediate part of the fourth ventricle; and (c) the isthmus rhombencephali, a constricted portion immediately adjoining the mid-brain and including the superior peduncles of the cerebellum, the anterior medullary velum, and the upper part of the fourth ventricle.
Developmentally considered, the fourth ventricle consists of three parts: a superior belonging to the isthmus rhombencephali, an intermediate, to the metencephalon, and an inferior, to the myelencephalon.
The cerebellum (metencephalon) consists of a central mass, the vermis (v. cbm.), and it also has lateral lobes (l.l.), prolonged into flocculi (f. cbm.), which lastare - em-bedded in pits, [in] the periotic bone, and on that account render the extraction of the brain from the cranium far more difficult than it would otherwise be.