Obex

The point on the midline of the dorsal surface of the medulla oblongata that marks the caudal angle of the rhomboid fossa.

A small triangular membrane at the caudal end of the roof of the fourth ventricle of the brain.

Brain: Obex
Hind-brain of a human embryo of three months—viewed from behind and partly from left side.
Rhomboid fossa.
Gray's	subject #187 797
NeuroNames	hier-633

For the protocol, see OBEX.

The obex (from the Latin for barrier) is the point in the human brain at which the fourth ventricle narrows to become the central canal of the spinal cord.

The obex occurs in the caudal medulla.

The decussating of sensory fibers happens at this point.

Clinical significance

Hemangioblastoma has been observed in this location.^[1]

References

1. ^ Pavesi G, Berlucchi S, Feletti A, Opocher G, Scienza R (July 2006). "Hemangioblastoma of the obex mimicking anorexia nervosa". Neurology 67 (1): 178–9. doi:10.1212/01.wnl.0000223354.86636.ed. PMID 16832109. http://www.neurology.org/cgi/pmidlookup?view=long&pmid=16832109. 

External links

• Photo at aphis.usda.gov (file not found as of 2008-08-16)

This neuroanatomy article is a stub. You can help Wikipedia by expanding it. v • d • e

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 · GSA: VIII-v (Lateral, Medial, Inferior) 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 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

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