Page 191 - Edited - Webster HEAD AND NECK - part 1

HN 157 THE EXTRAOCULAR MUSCLES (1)
HN 157

Each eye is moved by SIX small skeletal muscles. One other skeletal muscle has its origin

the orbit and lifts the upper eyelid. This movement is an intrinsic part of shifting the gaze
upwards (its absence is pathological). ALL SEVEN OF THESE MUSCLES ARE
SUPPLIED BY THREE CRANIAL NERVES, as indicated below.

(A) THE FOUR RECTUS MUSCLES These arise from a tendinous ring
around the OPTIC CANAL & LOWER PART OF THE INFERIOR ORBITAL
FISSURE. They are therefore arranged like four basket ribs AROUND THE OPTIC
NERVE AND POSTERIOR PART OF THE EYEBALL.
SUPERIOR
SUPERIOR RECTUS ORBITAL
MUSCLE FISSURE
MEDIAL Cr N III
(NASAL) OPTIC LATERAL
CANAL
LATERAL (TEMPORAL)
MEDIAL RECTUS
RECTUS MUSCLE Cr N VI
MUSCLE (ABDUCENT)
Cr N III

TENDINOUS
RING THE SIX EXTRAOCULAR
MUSCLES ARE GROUPED INTO
INFERIOR THE FOUR RECTUS
RECTUS MUSCLE (“STRAIGHT”) AND THE TWO
CON III (OCULOMOTOR) KEW. OBLIQUE MUSCLES.

(B) THE TWO OBLIQUE MUSCLES & LEVATOR PALPEBRAE SUPERIORIS

LEVATOR PALPEBRAE
THE TROCHLEA (“PULLEY”) OF
SUPERIOR OBLIQUE MUSCLE SUPERIORIS MUSCLE (“LIFTER OF THE
UPPER LID MUSCLE”) Cr N III

REDIRECTED TENDON
OF SUPERIOR OBLIQUE
SUPERIOR OBLIQUE MUSCLE, running laterally
MUSCLE CrN IV at anteriorly
(TROCHLEAR)

MEDIAL LATERAL
(NASAL)
(TEMPORAL)

This pattern of
extraocular muscles
is common to all
vertebrates. INFERIOR OBLIQUE
KEW MUSCLE - directed laterally
and slightly backwards. Cr N III
(OCULOMOTOR)