The Trochlear Nerve

From WikiMD

Anatomy > Gray's Anatomy of the Human Body > IX. Neurology > 5d. The Trochlear Nerve (N. Trochlearis; Fourth Nerve)

Henry Gray (1821–1865). Anatomy of the Human Body. 1918.

The Trochlear Nerve

(N. Trochlearis; Fourth Nerve)


The trochlear nerve (Fig. 776), the smallest of the cranial nerves, supplies the Obliquus superior oculi. It arises from a nucleus situated in the floor of the cerebral aqueduct, opposite the upper part of the inferior colliculus.

From its origin it runs downward through the tegmentum, and then turns backward into the upper part of the anterior medullary velum. Here it decussates with its fellow of the opposite side and emerges from the surface of the velum at the side of the frenulum veli, immediately behind the inferior colliculus.

The nerve is directed across the superior cerebellar peduncle, and then winds forward around the cerebral peduncle, immediately above the pons, pierces the dura mater in the free border of the tentorium cerebelli, just behind, and lateral to, the posterior clinoid process, and passes forward in the lateral wall of the cavernous sinus, between the oculomotor nerve and the ophthalmic division of the trigeminal.

It crosses the oculomotor nerve, and enters the orbit through the superior orbital fissure. It now becomes the highest of all the nerves, and lies medial to the frontal nerve. In the orbit it passes medialward, above the origin of the Levator palpebrae superioris, and finally enters the orbital surface of the Obliquus superior.


image776.gif


FIG. 776– Nerves of the orbit. Seen from above. (Picture From the Classic Gray's Anatomy)

In the lateral wall of the cavernous sinus the trochlear nerve forms communications with the ophthalmic division of the trigeminal and with the cavernous plexus of the sympathetic.

In the superior orbital fissure it occasionally gives off a branch to the lacrimal nerve. It gives off a recurrent branch which passes backward between the layers of the tentorium cerebelli and divides into two or three filaments which may be traced as far as the wall of the transverse sinus.

Function

The trochlear nerve provides motor supply to the superior oblique muscle of the eye,The trochlear nerve carries axons of type GSE, general somatic efferent, which innervate skeletal muscle of the superior oblique muscle.

The superior oblique muscle ends in a tendon that passes through a fibrous loop, the trochlea, located anteriorly on the medial aspect of the orbit. Trochlea means “pulley” in Latin; the fourth nerve is named after this structure.

Additional images

External links

Gray's Anatomy

Anatomy atlases (external)

[1] - Anatomy Atlases

Wikipedia
W8MD weight loss logo

Ad. Tired of being overweight?. W8MD's insurance Weight loss program can HELP*

Other languages:
English

Quick links: Medicine Portal | Encyclopedia‏‎‏‎ | Gray's Anatomy‏‎ | Topics‏‎ |‏‎ Diseases‏‎ | Drugs | Wellness | Obesity‏‎ | Metabolic syndrome | Weight loss*
Disclaimer: The entire contents of WIKIMD.ORG are for informational purposes only and do not render medical advice or professional services. If you have a medical emergency, you should CALL 911 immediately! Given the nature of the wiki, the information provided may not be accurate, misleading and or incorrect. Use the information on this wiki at your own risk! See full Disclaimer.
Link to this page: <a href="http://www.wikimd.org/wiki/The_Trochlear_Nerve">The Trochlear Nerve</a>

  • Individual results may vary for weight loss from our sponsors.