Page 534 - Fundamentals of anatomy physiology

Figure 14–22 Cranial Nerves Controlling the Extrinsic Eye Muscles. ATLAS: Plates 16a,b

Superior Superior rectus Optic nerve Optic Oculomotor Trochlear nerve
oblique muscle (N II) chiasm nerve (N III) (N IV)
muscle

Trochlea

Levator
palpebrae
superioris

muscle

Inferior Trigeminal
oblique nerve (N V), cut
muscle
Vestibulocochlear
Inferior Medial nerve (N VIII), cut
rectus Ciliary rectus
muscle ganglion muscle Facial nerve
(N VII), cut

Lateral rectus Abducens
muscle (cut) nerve (N VI)

The Trochlear Nerves (IV) The Abducens Nerves (VI)

Primary function: Motor (eye movements) Primary function: Motor (eye movements)

Origin: Midbrain Origin: Pons

Pass through: Superior orbital fissures of sphenoid Pass through: Superior orbital fissures of sphenoid pp. 237,
pp. 237, 243, 246, 249 243, 246, 249

Destination: Superior oblique muscle Destination: Lateral rectus muscle

A trochlear (TRO. K-le. -ar; trochlea, a pulley) nerve (IV), the small- The abducens (ab-DU. -senz) nerves (VI) innervate the lateral
est cranial nerve, innervates the superior oblique muscle of each rectus muscles, the sixth pair of extrinsic eye muscles. Contrac-
eye (Figure 14–22). The trochlea is a pulley-shaped, ligamentous tion of the lateral rectus muscle makes the eye look to the side.
sling. Each superior oblique muscle passes through a trochlea In essence, the abducens causes abduction of the eye. Each
on its way to its insertion on the surface of the eye. An individual abducens nerve emerges from the inferior surface of the brain
with damage to cranial nerve IV or to its nucleus has difficulty stem at the border between the pons and the medulla oblongata
looking down and to the side. (Figure 14–22). Along with the oculomotor and trochlear nerves
from that side, it reaches the orbit through the superior orbital
fissure.

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