Nucleus ambiguus
| Nucleus ambiguus | |
|---|---|
 Transverse section of medulla oblongata below the middle of the olive. ("Nucleus ambiguus" labeled at center right.) | |
| Details | |
| Identifiers | |
| Latin | nucleus ambiguus |
| NeuroNames | 765 |
| NeuroLex ID | birnlex_2650 |
| TA98 | A14.1.04.253 |
| TA2 | 6011 |
| FMA | 54588 |
| Anatomical terms of neuroanatomy | |
The nucleus ambiguus is a group of large motor neurons situated in the reticular formation of the medulla oblongata of the brainstem.[1] It represents a shared cranial nerve nucleus of the glossopharyngeal nerve (CN IX), and vagus nerve (CN X);[2]: 103 the cranial root of accessory nerve (CN XI) is now also considered as (displaced) fibers of CN X arising from the caudal nucleus ambiguus to travel some distance with those of the (spinal root of) CN XI before joining the main CN X.[2]: 345
Lower motor neurons of the nucleus ambiguus ipsilaterally innervate muscles of the soft palate, pharynx, larynx, and upper esophagus; they are thus involved in speech and swallowing.[citation needed]
Anatomy
[edit]The nucleus is situated dorsal/posterior to the inferior olivary nucleus, and lateral to the medial lemniscus.[2]: 103 It is situated near the facial motor nucleus.[1]
Efferent fibers from the nucleus ambiguus pass dorsomedially before curving laterally. The rostral portion of nucleus ambiguus contributes fibers to CN IX, and the caudal portion to CN X.[1]
Connections
[edit]The nucleus receives bilateral (but mostly contralateral) upper motor neuron afferents via corticonuclear fibers.[1] The fibers destined for the nucleus ambiguus mostly diverge from the corticonuclaer tract at the level of the caudal pons and rostral medulla oblongata, however, some descend alongside the corticospinal tract to reach and decussate at the pyramidal decussation before reascending to reach the nucleus ambiguus.[2]: 240
The nucleus also forms reciprocal connections with other nuclei of the brainstem.[1]
Innervation
[edit]This nucleus gives rise to the branchial efferent motor fibers of the CN X innervating laryngeal and pharyngeal muscles, and musculus uvulae;[3] axons from the nucleus ambiguus passing in the CN IX innervate the stylopharyngeus muscle.[citation needed]
Clinical significance
[edit]Lesions of nucleus ambiguus result in dysphagia, dysphonia,[2]: 115 and contralateral deviation of the uvula.[2]: 118
Additional images
[edit]-
Section of the medulla oblongata at about the middle of the olive. -
The cranial nerve nuclei are schematically represented; in dorsal view. Motor nuclei in red; sensory in blue. -
Nuclei of origin of cranial motor nerves schematically represented; lateral view. -
The formatio reticularis of the medulla oblongata, shown by a transverse section passing through the middle of the olive.
See also
[edit]References
[edit]- ^ a b c d e Standring, Susan (2020). Gray's Anatomy: The Anatomical Basis of Clinical Practice (42th ed.). New York: Elsevier. p. 449. ISBN 978-0-7020-7707-4. OCLC 1201341621.
- ^ a b c d e f Patestas, Maria A.; Gartner, Leslie P. (2016). A Textbook of Neuroanatomy (2nd ed.). Hoboken, New Jersey: Wiley-Blackwell. ISBN 978-1-118-67746-9.
- ^ Petko, Bogdana; Tadi, Prasanna (2024), "Neuroanatomy, Nucleus Ambiguus", StatPearls, Treasure Island (FL): StatPearls Publishing, PMID 31613524, retrieved 2024-05-03
External links
[edit]- Medical Neurosciences discusses the nucleus ambiguus.
