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.

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]

Contents 1 Myelencephalon 2 Metencephalon 3 Additional images 4 References 5 External links

[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] Additional images

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

Embryo between eighteen and twenty-one days.

[edit] References

1. ^ SpringerLink - Journal Article

[edit] External links

• NIF Search - Rhombencephalon via the Neuroscience Information Framework

Look up rhombencephalon in Wiktionary, the free dictionary.

v • d • e Nervous system (TA A14, GA 9) Central nervous system Meninges Spinal cord Brain: Rhombencephalon (Medulla oblongata, Pons, Cerebellum) • Mesencephalon • Prosencephalon (Diencephalon, Telencephalon) Peripheral nervous system Somatic Sensory nerve • Motor nerve • Cranial nerves • Spinal nerves Autonomic Sympathetic • Parasympathetic • Enteric nervous system central nervous system navs: anat/physio/dev, noncongen/congen/neoplasia, symptoms+signs/eponymous, proc peripheral nervous system navs: anat/histo/physio/dev, noncongen PNS somatic/autonomic/congen/neoplasia, symptoms+signs/eponymous, proc

v • d • e Human brain: rhombencephalon, myelencephalon: medulla (TA A14.1.04, GA 9.767) Dorsal Surface Posterior median sulcus · Posterolateral sulcus · Area postrema · Vagal trigone · Hypoglossal trigone · Medial eminence Grey: Cranial nuclei afferent: GVA: VII,IX,X: Solitary/tract/Dorsal respiratory group · SVA: Gustatory nucleus efferent: GSE: XII  · GVE: IX,X,XI: Ambiguus · SVE: X: Dorsal · IX: Inferior salivatory nucleus Grey: other Gracile nucleus · Cuneate nucleus (Accessory cuneate nucleus) White: Sensory/ascending Sensory decussation  · Medial lemniscus · Inferior cerebellar peduncle (Juxtarestiform body) · Ascending dorsal longitudinal fasciculus · MLF, III, IV and VI White: Motor/descending Descending dorsal longitudinal fasciculus · MLF, III, IV and VI Ventral White: Motor/descending Motor decussation · Olivocerebellar tract · Rubro-olivary tract Grey matter Ventral respiratory group · Arcuate nucleus of medulla · Inferior olivary nucleus Surface Anterior median fissure · Antero-lateral sulcus · Olive · Pyramid Grey: Raphe/ reticular Reticular formation (Gigantocellular, Parvocellular, Ventral, Lateral, Paramedian) · Raphe nuclei (Obscurus, Magnus, Pallidus)

v • d • e Human brain, rhombencephalon, metencephalon: pons (TA A14.1.05.101-604, GA 9.785) Dorsal/ (tegmentum) Surface Cerebellopontine angle · Superior medullary velum · Sulcus limitans · Medial eminence · Facial colliculus White: Sensory/ascending Trapezoid body/VIII · Trigeminal lemniscus (Dorsal trigeminal tract, Ventral trigeminal tract) · Medial lemniscus · Lateral lemniscus MLF, III, IV and VI: Vestibulo-oculomotor fibers Anterior trigeminothalamic tract · Central tegmental tract White: Motor/descending ICP (Vestibulocerebellar tract) MLF, III, IV and VI: Vestibulospinal tract (Medial vestibulospinal tract, Lateral vestibulospinal tract) Grey: Cranial nuclei afferent: GSA: Principal V/Spinal V · VIII-c (Dorsal, Anterior)/VIII-v (Lateral, Superior, Medial, Inferior) efferent: SVE: Motor V  · VII · GSE: VI · GVE: VII: Superior salivary nucleus Other grey Apneustic center · Pneumotaxic center (Medial parabrachial nucleus) · Lateral parabrachial nucleus · Superior olivary nucleus · Caerulean nucleus Ventral/ (base) Grey Pontine nuclei White: Motor/descending Corticospinal tract · Corticobulbar tract · Corticopontine fibers MCP (Pontocerebellar fibers) Surface Basilar sulcus Other grey: Raphe/ reticular Reticular formation (Caudal, Oral, Tegmental, Paramedian) · Raphe nuclei (Median)

v • d • e Ventricular system, rhombencephalon, met- and myel-: fourth ventricle (TA A14.1.05.701-726, GA 9.797) Roof (dorsal) rostral: Superior medullary velum (Frenulum) caudal: Inferior medullary velum · Taenia of fourth ventricle Floor/rhomboid fossa (ventral) rostral (pons): Facial colliculus · Locus coeruleus caudal (medulla}: Vagal trigone · Hypoglossal trigone · Area postrema · Obex Medial eminence · Sulcus limitans Apertures Median/Magendie · Lateral recess to Lateral/Luschka Other Tela chorioidea of fourth ventricle · Fastigium

v • d • e Human brain, rhombencephalon, metencephalon: cerebellum (TA 14.1.07, GA 9.788) Surface anatomy Posterior lobe (Horizontal fissure) · Anterior lobe · Flocculonodular lobe (Flocculus, Nodule) Vermis: posterior (Folium, Tuber, Uvula) · anterior (Central lobule, Culmen, Lingula) Hemisphere: posterior (Biventer lobule, Cerebellar tonsil) · anterior (Alar central lobule) Vallecula of cerebellum · Primary fissure Grey matter Deep cerebellar nuclei Dentate · interposed (Emboliform, Globose) · Fastigial Cerebellar cortex Molecular layer (Stellate cell, Basket cell) Purkinje cell layer (Purkinje cell, Bergmann glia cell = Golgi epithelial cell) Granule cell layer (Golgi cell, Granule cell, Unipolar brush cell) Fibers: Mossy fibers · Climbing fiber · Parallel fiber White matter Internal Arbor vitae Peduncles Inferior (medulla): Dorsal spinocerebellar tract · Olivocerebellar tract · Cuneocerebellar tract · Juxtarestiform body (Vestibulocerebellar tract) Middle (pons): Pontocerebellar fibers Superior (midbrain): Ventral spinocerebellar tract · Dentatothalamic tract · Trigeminocerebellar fibers

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