What is an Oculomotor Nerve?

That is, the third pair of brain nerves is a motor brain nerve, which contains two kinds of fibers: body movement and visceral movement. It starts from the ventral interoccipital fossa of the midbrain, close to the margin of the cerebellar notch and the lateral side of the posterior sphenoid saddle, and passes through the upper side wall of the cavernous sinus. Adjust reflection and pupil reflection on light.

That is, the third pair of brain nerves is a motor brain nerve, which contains two kinds of fibers: body movement and visceral movement. It starts from the ventral interoccipital fossa of the midbrain, close to the margin of the cerebellar notch and the lateral side of the posterior sphenoid saddle, and passes through the upper side wall of the cavernous sinus. Adjust reflection and pupil reflection on light.

Chinese name

oculomotor nerve

Foreign name

oculomotor nerve

Belong to

Motor nerve

Contains

Body and visceral fibers

Oculomotor nerve

The oculomotor nucleus is located in the gray matter on the ventral side around the aqueduct at the level of the superior quadrant of the midbrain. Fibers from the nucleus pass through the medial longitudinal bundle, red nucleus, and substantia nigra to the ventral side, and leave the brain stem between the medial side of the brain's feet, between the posterior cerebral artery and the superior cerebellar artery. It passes through the dura mater in the small triangular area between the free and fixed margin of the cerebellum near the sacral posterior process and enters the cavernous sinus at the outer upper corner of the sinus, then divides into two branches via the supraorbital fissure. Eyes. The upper branch supplies the superior levator muscle and the upper rectus muscle, and occasionally some fibers reach the oculi orbicularis muscle; the lower branch supplies the inner rectus muscle, the lower rectus muscle, and the inferior oblique muscle, and provides the short roots of the ciliary ganglia, the latter's Postganglionic fibers make up the short ciliary nerve to supply the pupil sphincter and ciliary muscle.

The oculomotor nucleus can be divided into three parts: the main nucleus of the lateral nucleus is the largest and contains large groups of neurons that dominate the levator muscle, upper rectus muscle, medial rectus muscle, lower oblique muscle, and lower rectus muscle, but related The location of the nucleus that dominates the ophthalmic muscles and their intersection have not yet been elucidated. The paired Ai-Wei nucleus is located at the posterior and medial sides of the lateral nucleus and is composed of smaller neurons. Its fibers control the pupil sphincter and ciliary muscle. There is still a medial nucleus between the lateral sides. Both the Ai-Wei core and the medial nucleus belong to the parasympathetic nervous system. Through these cores, the oculomotor nerve participates in some pupil reflex activities.

Oculomotor nerve anatomy:

(A) Segmentation:

The researchers divided the oculomotor nerve into five segments, which are the pool segment, rock bed segment, cavernous sinus segment, supraorbital fissure segment, and orbital segment. The segmentation criteria are as follows: The pool segment is located after the oculomotor nerve leaves the midbrain. The outer side of the inter-foot fossa exits the cerebral foot and runs to the anterolateral and upper part of the posterior bed ligament. Bedrock section: from the posterior bedrock ligament to the entrance of the dura mater into the cavernous sinus. cavernous sinus segment: from the oculomotor sinus to the cavernous sinus to the lower edge of the anterior bed process tip or forward. supraorbital fissure segment: from the oculomotor nerve into the supraorbital fissure to the supraorbital fissure. Orbital segment: the oculomotor nerve through the superior orbital fissure to the upper and lower branches respectively dominate the eye muscles.

(B) the relationship between the pool segment and the surrounding blood vessels:

The oculomotor nerve is closely related to the surrounding blood vessels after exiting the intercondylar fossa. The blood vessels on its ventral side include the small branches of the basilar artery, the superior cerebellar artery, the posterolateral pontine artery, and the perforating branches of these arteries. The superior cerebellar artery starts at the end of the basilar artery and travels laterally at the ventral level of the oculomotor nerve. The posterolateral pontine artery starts from the basilar artery on the caudal side of the superior cerebellar artery, runs horizontally outward from the dorsal side of the superior cerebellar artery, and is located on the caudal side of the oculomotor nerve. The perforating branch from the above artery enters the posterior fossa and walks on the ventral side of the oculomotor nerve root.

The adjacent vessels on the back of the oculomotor nerve segment are the posterior cerebral artery, posterior communicating artery, and thalamus. The posterior cerebral artery is the terminal branch of the basilar artery, and the oculomotor nerve is usually in contact with the medial trunk of the intersocial fossa. The posterior communication artery originates from the internal carotid artery, passes under the optic tract, and coincides with the posterior cerebral artery. Generally, the posterior cerebral artery is separated from the oculomotor nerve root without contacting it. The thalamus usually starts from the caudal side of the posterior cerebral artery, runs between the posterior cerebral artery and the oculomotor nerve, and contacts the oculomotor nerve across it. The parathalamic artery is a branch of the thalamic artery, and part of it is also adjacent to the back of the oculomotor nerve segment. In addition, there is a posterior choroidal medial artery, a midbrain, and a mesencephalic perforating branch adjacent to the oculomotor nerve segment.