The eye muscles and movements

Question 1

what is the function of the intrinsic and extrinsic muscles of the eyes?

Answer 1

intrinsic control pupil diameter and help to alter lens curvature for seeing near objects
extrinsic move the eye

Question 2

what are the intrinsic muscles and where are they found?

Answer 2

ciliaris muscle - within ciliary body
constrictor pupillae - in the iris and the pupillary border
dilator pupillae - radiating in the iris

Question 3

what is the nerve innervation of the intrinsic muscles?

Answer 3

ciliaris & constrictor pupillae = parasympathetic occulomotor CN III
dilator pupillae = sympathetic plexus

Question 4

what are the extrinsic muscles and their nerve supply?

Answer 4

superior, inferior, medial and lateral rectus
superior and inferior oblique
superior oblique CN IIII - trochlear nerve
lateral rectus CN VI - abducent nerve
everything else CN III - occulomotor nerve

Question 5

what are the attachments of the extrinsic muscles?

Answer 5

they all attach posteriorly and come forward to act on the eye except the superior oblique which attaches anteriorly

Question 6

what is the origin and insertion of the oblique muscles?

Answer 6

superior oblique;
origin = floor of orbit posteriorly (lesser wing os sphenoid)
insertion = sclera posteriorly
inferior oblique;
origin = medial part of orbit floor (floor of orbit anteriorly)
insertion = sclera posteriorly

Question 7

what are the actions of the superior oblique?

Answer 7

intorsion
depression
abduction

Question 8

what are the actions of the inferior oblique?

Answer 8

abduction
extorsion
elevation

Question 9

what are the action(s) of the medial rectus?

Answer 9

adduction

Question 10

what are the action(s) of the lateral rectus?

Answer 10

abduction

Question 11

what are the actions of the superior rectus?

Answer 11

adduction
intorsion
elevation

Question 12

what are the actions of the inferior rectus?

Answer 12

depression
adduction
extorsion

Question 13

why do the rectus muscles (except medial and lateral) have more than one action?

Answer 13

they are attached along the orbital axis not the optical axis so they pull on the eyeball at and angle

Question 14

when the medial rectus has abducted the eye, what action does the superior and inferior rect cause?

Answer 14

superior rectus causes intorsion

inferior rectus causes extorsion

Question 15

when the eyeball is abducted what muscles causes intorsion and extortion?

Answer 15

superior oblique causes intorsion

inferior oblique causes extorsion

Question 16

which muscles elevate and depress the eye when;

1. it is abducted?
2. it is adducted?

Answer 16

1. superior and inferior oblique

2. superior and inferior retctus