Rhombencephalon
| Brain: Rhombencephalon | ||
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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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| Scheme of roof of fourth ventricle. | ||
| Gray's | subject #187 767 | |
| NeuroNames | hier-531 | |
| MeSH | Rhombencephalon | |
| NeuroLex ID | birnlex_942 | |
The rhombencephalon (or hindbrain) is a developmental categorization of portions of the central nervous system in vertebrates. It includes the medulla, pons, and cerebellum.
The rhombencephalon can be subdivided in a variable number of transversal swellings called rhombomeres. In the human embryo eight rhombomeres can be distinguished, from caudal to rostral: Rh7-Rh1 and the isthmus (the most rostral rhombomere).
A rare disease of the rhombencephalon, "rhombencephalosynapsis," is characterized by a missing vermis resulting in a fused cerebellum. Patients generally present with cerebellar ataxia.
The caudal rhombencephalon has been generally considered as the initiation site for neural tube closure.[1]
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[edit] Myelencephalon
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).
[edit] Metencephalon
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).
[edit] Evolution
The hindbrain is homologous to a part of the arthropod brain known as the sub-oesophageal ganglion.[2] On this basis, it has been suggested that the hindbrain first evolved in the Urbilaterian - the last common ancestor of chordates and arthropods - between 570 and 555 million years ago.[2][3]
[edit] Additional images
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Chick embryo of thirty-three hours’ incubation, viewed from the dorsal aspect. X 30.
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Embryo between eighteen and twenty-one days.
[edit] References
- Haycock DE (2011). Being and Perceiving. Manupod Press. ISBN 9780956962102. http://books.google.co.uk/books?id=fXFeQb1z6bsC.
- ^ SpringerLink - Journal Article
- ^ a b Ghysen A (2003). "The origin and evolution of the nervous system". Int. J. Dev. Biol. 47 (7–8): 555–62. PMID 14756331. http://www.ijdb.ehu.es/web/paper.php?doi=14756331.
- ^ Haycock, DE Being and Perceiving
[edit] External links
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Look up rhombencephalon in Wiktionary, the free dictionary. |
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