Objectives:
Describe the attachment of extra-ocular muscles.
Describe the action and nerve supply of extra-ocular muscles.
Extra-ocular muscles of eye
The muscle acting on the eye ball to produce various
movements of eye are called extr-aocular muscles which consists of
Four recti
|
Two oblique muscles
|
Superior rectus
|
Superior oblique
|
Inferior rectus
|
Inferior oblique
|
Medial rectus
|
|
Lateral rectus
|
Recti muscles
Origin – from posterior part
of the orbit from a common tendinous ring
Insertion – the muscles
proceed forwards in a cone of muscles and spread out at the sites of insertion
into the sclera of the eyeball.
Oblique Muscles
Superior oblique: arises
from the lesser wing of sphenoid bone and inserts into the sclera behind the
equator of eyeball.
Inferior Oblique: arises
from orbital surface of maxilla in the floor of the orbit and inserts into the
sclera behind the equator of the eyeball.
Innervations or Nerve supply of extra-ocular muscles
All these muscles are supplied by oculomotor nerve
(Cranial Nerve III) except lateral rectus (by abducent nerve – CN VI)
and superior rectus (by trochlear nerve – CN IV).
Actions of extra-ocular muscles
Superior rectus –elevates, adducts
and medially rotates the eyeball
Inferior rectus –depresses, adducts
and medially rotates the eyeball
Medial rectus – adducts the eyeball
Lateral rectus – abducts the
eyeball
Superior oblique – depresses,
abducts and medially rotate the eye ball
Inferior oblique – elevates,
abducts and laterally rotate the eyeball.
REFERENCES:
REFERENCES:
Following resources are used while preparing this post (readers are strongly recommended to go through them for more details):
K. L. Moore's Clinically Oriented Anatomy
R. Snell's Clinical Anatomy