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Rhombencephalon
From Wikipedia, the free encyclopedia
Brain: Rhombencephalon
GraySubject = 187 |
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| Diagram depicting the main subdivisions of the embryonic vertebrate brain. These regions will later differentiate into forebrain, midbrain and hindbrain structures. | ||
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| Superficial dissection of brain-stem. Lateral view. | ||
| NeuroNames | hier-531 | |
| MeSH | Rhombencephalon | |
| Dorlands/Elsevier | r_12/12709581 | |
The rhombencephalon (or hindbrain) is a developmental categorization of portions of the central nervous system in vertebrates.
The rhombencephalon can be subdivided in a variable number of transversal swellings called rhombomeres. In the human embryo we can distinguish eight rhombomeres, from caudal to rostral: Rh7-Rh1 and the isthmus (the most rostral rhombomere).
A rare disease of the rhomencephalon, "rhombencephalosynapsis" is characterized by a missing vermis resulting in a fused cerebellum. Patients generally present with cerebellar ataxia.
Rhombomeres Rh7-Rh4 form the myelencephalon.
The myelencephalon forms the medulla oblongata in the adult brain; it contains:
- a portion of the fourth ventricle,
- the glossopharyngeal nerve (CN IX),
- vagus nerve (CN X),
- accessory nerve (CN XI),
- hypoglossal nerve (CN XII),
- and a portion of the vestibulocochlear nerve (CN VIII).
Rhombomeres Rh3-Rh1 form the metencephalon.
The metencephalon is composed of the pons and the cerebellum; it contains:
- a portion of the fourth ventricle,
- the trigeminal nerve (CN V),
- abducens nerve (CN VI),
- facial nerve (CN VII),
- and a portion of the vestibulocochlear nerve (CN VIII).
 Chick embryo of thirty-three hours’ incubation, viewed from the dorsal aspect. X 30. |
 Embryo between eighteen and twenty-one days. |
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