Embedded Files
Location: The nuclear area lies in the periaqueductal gray matter of the midbrain, ventral to the aqueduct, at the level of the superior colliculi.
Nuclei: It has two major components:
a medially situated parasympathetic nucleus, (Edinger- Westphal nucleus or accessory autonomic nucleus) - innervates the intraocular muscles (the sphincter pupillae muscle and the ciliary muscle);
a larger and more laterally situated nuclear complex for four of the six extraocular muscles (the superior, inferior, and medial rectus muscles and the inferior oblique muscle).There is also a small nuclear area for the levator palpebrae muscle (cf. Warwick’s diagram of the simian oculomotor nuclear complex).
Topography
The motor radicular fibers that emerge from these nuclear areas travel ventrally together with the parasympathetic fibers; some of them cross the midline, others do not (all of the fibers for the superior rectus muscle cross the midline).
The combined motor and parasympathetic fibers traverse the red nucleus and finally exit the brainstem in the interpeduncular fossa as the oculomotor nerve.
The oculomotor nerve first runs posteriorly between the superior cerebellar and PCA, in close apposition to the tentorial edge, then penetrates the dura mater, traverses the cavernous sinus, and enters the orbit through the superior orbital fissure.
The parasympathetic portion of the nerve branches off at this point and travels to the ciliary ganglion, where the preganglionic fibers terminate and the ganglion cells give off short postganglionic fibers to innervate the intraocular muscles.
The somatic motor fibers of the oculomotor nerve divide into two branches:
a superior branch supplying the levator palpebrae and superior rectus muscles,
and an inferior branch supplying the medial and inferior recti and the inferior oblique muscle.
Page updated
Google Sites
Report abuse