+ All Categories
Home > Documents > The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

Date post: 12-Jan-2016
Category:
Upload: alice-ford
View: 224 times
Download: 3 times
Share this document with a friend
Popular Tags:
16
Transcript
Page 1: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.
Page 2: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

The Occulomotor, Trochlear & Abducent Cranial Nerves

Dr. NimirDr. Safaa

Page 3: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

Objectives

• Discuss the central connections of the Occulomotor(III)

nerve.• Discuss the central connections of the

trochlear(IV) nerve.• Discuss the central connections of the

abducent(III,IV,VI) nerve.

Page 4: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

• Oculomotor Nerve (Cranial Nerve III)

• Oculomotor nerve is entirely motor in function.

• Has two motor nuclei: • Main motor nucleus.• Accessory

parasympathetic nucleus.• Main nucleus is anterior

to cerebral aqueduct at level of superior colliculus.

• It supplies all extrinsic muscles of eye except superior oblique and lateral rectus.

Page 5: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

• Main nucleus receives:• Corticonuclear fibers

from both cerebral hemispheres.

• Tectobulbar fibers from superior colliculus (information from visual cortex).

• It is connected to nuclei of fourth, sixth, and eighth cranial nerves by medial longitudinal fasciculus.

Page 6: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

• Accessory parasympathetic nucleus (Edinger-Westphal nucleus) is posterior to main nucleus.

• Preganglionic fibers accompany other oculomotor fibers to orbit & synapse in ciliary ganglion.

• Postganglionic fibers pass through short ciliary nerves to constrictor pupillae of iris and ciliary muscles.

• Accessory nucleus receives corticonuclear fibers for accommodation reflex and from pretectal nucleus for the direct and consensual light reflexes.

Page 7: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

• Course of Oculomotor Nerve

• Oculomotor fibers passes through red nuleus and emerge between cerebral peduncles & pass forward between posterior cerebral and superior cerebellar arteries.

• It then continues into the middle cranial fossa in lateral wall of cavernous sinus. Here, it divides into a superior and an inferior branches, which enter the orbital cavity through superior orbital fissure.

Page 8: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

• Oculomotor nerve supplies levator palpebrae superioris, superior rectus, medial rectus, inferior rectus, and inferior oblique.

• It also supplies, through parasympathetic fibers, constrictor pupillae of iris and ciliary muscles.

• It is responsible for lifting upper eyelid, turning eye upward, downward, and medially.

• Constricting pupil and accommodating the eye.

Page 9: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

Trochlear Nerve • Trochlear nerve is entirely

motor in function.• Trochlear Nerve Nucleus:• The trochlear nucleus is

situated anterior to cerebral aqueduct.

• It lies inferior to oculomotor nucleus at level of inferior colliculus. The nerve fibers, after leaving nucleus, pass posteriorly to reach posterior surface of midbrain.

Page 10: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

• The trochlear nucleus receives

• Corticonuclear fibers from both cerebral hemispheres.

• It receives:• Tectobulbar fibers, which

connect it to visual cortex through superior colliculus.

• Fibers from medial longitudinal fasciculus, by which it is connected to nuclei of third, sixth, and eighth cranial nerves.

Page 11: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

• Course of the Trochlear Nerve

• Trochlear , most slender cranial nerves and the only one to leave posterior surface of brainstem.

• Emerges from midbrain and immediately decussates with that of opposite side.

Page 12: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

• Trochlear nerve passes forward through middle cranial fossa in lateral wall of cavernous sinus and enters orbit through superior orbital fissure.

• Trochlear nerve supplies superior oblique muscle of eyeball.

• Trochlear nerve assists in turning eye downward and laterally.

Page 13: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

• Abducent Nerve (Cranial Nerve VI):

• It is entirely motor in function.• Abducent has small motor

nucleus situated beneath floor of upper part of fourth ventricle, close to midline and beneath facial colliculus.

• The nucleus receives:• Afferent corticonuclear fibers

from both cerebral hemispheres. • Tectobulbar tract from superior

colliculus, by which it is connected to visual cortex.

• Fibers from medial longitudinal fasciculus, by which it is connected to the nuclei of third, fourth, and eighth cranial nerves.

Page 14: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

• Course of the Abducent Nerve

• Abducent fibers pass anteriorly through pons and emerge in groove between lower border of pons and medulla oblongata.

• It passes forward through cavernous sinus, lying below and lateral to internal carotid artery.

Page 15: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

• The nerve then enters orbit through superior orbital fissure.

• Abducent supplies lateral rectus muscle and, therefore, is responsible for turning eye laterally.

Page 16: The Occulomotor, Trochlear & Abducent Cranial Nerves Dr. Nimir Dr. Safaa.

Recommended