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The trochlear and abducens nerves

The trochlear nerve is the fourth of the twelve cranial nerves, whereas the abducens nerve is the sixth. They both consist of afferent and efferent motoric fibers.

The word afferent means 'toward the centre', as in 'from a peripheral area of a limb to the central nervous system'. The word efferent is the opposite of efferent, meaning 'away from the centre' and toward the periphery.

Recommended video: Oculomotor, trochlear and abducens nerves
Course of the oculomotor, abducens and trochlear nerves.

Course and Innervation

Trochlear nerve

The pathway for fibers of the trochlear nerve is the following (from the initiation in the brain to the termination in the periphery):

Trochlear nerve - lateral view

Trochlear nerve - lateral view

Abducens nerve

The pathway for the fibers of the abducens nerve is the following (from the initiation in the brain to the termination in the periphery):

  • The nucleus of the abducent nerve can be found in the facial colliculus of the brainstem.
  • It exits the skull via the superior orbital fissure.
  • It innervates the lateral rectus muscle of the eye.
  • This nerve governs the muscle responsible for abduction (lateral movement) of the eye within the orbit.

Abducens nerve - lateral view

Abducens nerve - lateral view

Summary

Trochlear nerve: Inferior colliculus -> Superior orbital fissure -> Superior oblique muscle.

Function: Abduction, depression, internal rotation of the eye.

Abducens nerve: Facial colliculus -> Superior orbital fissure -> Lateral rectus muscle.

Function: Abduction (lateral movement) of the eye.

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Show references

Reference:

  • Frank H. Netter, Atlas der Anatomie, 5th Edition (Bilingual Edition: English and German), Saunders, Kapitel 1, Tafel 113, 115 and 120, Published 2010.

Author:

  • Dr. Alexandra Sierosławska

Illustrators:

  • Trochlear nerve - lateral view - Paul Kim
  • Abducens nerve - lateral view - Paul Kim
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Oculomotor, trochlear and abducens nerves

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