Rhombencephalon

Brain: Rhombencephalon
Diagram depicting the main subdivisions of the embryonic vertebrate brain. These regions will later differentiate into forebrain, midbrain and hindbrain structures.
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.

Rhombencephalon

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]

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).

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).

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]

Additional images

• 

  Chick embryo of thirty-three hours’ incubation, viewed from the dorsal aspect. X 30.

• 

  Embryo between eighteen and twenty-one days.

References

• Haycock DE (2011). Being and Perceiving. Manupod Press. ISBN 9780956962102. http://books.google.co.uk/books?id=fXFeQb1z6bsC. 

1. ^ SpringerLink - Journal Article
2. ^ ^{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. 
3. ^ Haycock, DE Being and Perceiving

External links

• NIF Search - Rhombencephalon via the Neuroscience Information Framework