EOM's

Question 1

Define origin and insertion

Answer 1

Origin- fixed attachment

Insertion- Moves with contraction

Question 2

Origin of the 4 rectus muscles

Answer 2

The common tendinous ring
Oval band of tissue formed by the tendons of the recti muscles and periorbita.

Anterior to the optic canal and anterior to the inferior part of the superior orbital fissure.

Question 3

The common tendinous ring is divided into which 2 thickened bands

What bands do the 4 recti muscles attach to?

Answer 3

The upper and lower.

The superior rectus attaches to the upper limb
The inferior rectus attaches to the lower limb
The medial rectus and the lateral rectus attach to the upper and lower limb

Question 4

Which two recti muscles attach to the common tendinous ring and also the dural sheath of the ON?

Answer 4

The superior rectus and medial rectus.

Question 5

Which recti muscle attaches to a prominence on the greater wing of the sphenoid?

Answer 5

The lateral rectus. Connects to the spina recti lateralis.

Question 6

Course of the medial rectus

Answer 6

Parallel to the medial orbital wall. Follows the curve of the globe until its insertion.

Sheath of the medial rectus forms the medial check ligament, which holds the globe in place.

Question 7

Course of the lateral rectus

Answer 7

Parallel to the lateral orbital wall. Follows the curve of the globe until its insertion.

Sheath of the lateral rectus forms the lateral check ligament, which holds the globe in place.

Question 8

Course of the superior rectus

Answer 8

Courses forward beneath the levator muscle.
Sheath enclosing these 2 muscles are connected. They work together to connect eyelid movement with eye movement (upper lid elevators when you gaze up).

Parallel to the roof, follows the curve of the globe until its insertion.

Question 9

Course of the inferior rectus

Answer 9

Courses forward above the inferior oblique. Sheath enclosing the inferior rectus and the inferior oblique forms the capsulopalpebral fascia, which connects eyelid movement with eye movement. (LL lowers on downsize and elevators on up gaze).

Parallel to the orbit floor, follows the curve of the globe until its insertion.

Question 10

Recti muscles become ___ prior to their insertions.

They penetrate ___ in order to attach to sclera

Answer 10

They become tendons prior to their insertions. They penetrate tenons capsule in order to attach to sclera. Tenon’s capsule will cover the tendons for a short distance.

Question 11

Medial rectus inserts where?

Which axis is it parallel to?

Answer 11

Inserts anteriorly and medially.

Parallel to the sagittal/visual/Y axis

Question 12

The lateral rectus inserts where?

Which axis is it parallel to?

Answer 12

The lateral rectus inserts anteriorly and laterally.

Parallel to the sagittal/visual/Y axis

Question 13

The superior rectus inserts where?

What angle does it form relative to the visual axis?

Answer 13

It inserts in the lateral, anterior, superior aspect of the globe.
What angle does it form relative to the visual axis?

Question 14

The inferior rectus inserts where?

What angle does it form relative to the visual axis?

Answer 14

The inferior rectus inserts in the lateral, anterior, inferior aspect of the globe.
What angle does it form relative to the visual axis?

Question 15

Muscle insertion to limbus distance

Answer 15

Medial rectus is the most anterior: 5.5mm
Inferior rectus: 6.5mm
Lateral rectus: 6.9mm
Superior rectus is the most posterior: 7.7

Question 16

What is the spiral of Tillaux

Answer 16

Muscle insertions to limbus forms a spiral of most anterior at the medial rectus to the most posterior at the superior rectus

Question 17

The superior oblique muscle originates where (2)

Answer 17

Originates at the lesser wing of the sphenoid bone just above the optic canal at the orbital apex.
Functional origin is at the trochlea

Question 18

Origin of the inferior oblique

Answer 18

Originates at the maxillary bone. Just posterior to the inferior medial orbital rim of the maxillary bone.

Question 19

Which is the only EOM to have origin in the anterior orbit?

Answer 19

The inferior oblique

Question 20

Course of the superior oblique muscle

Answer 20

Courses along the medial wall
Muscle changes to tendon near the superior medial orbital wall
Passes through trochlea, which is a U shaped cartilage in the trochlear fossa located in the frontal bone medially.
Courses beneath the superior rectus.

Question 21

Course of the inferior oblique muscle

Answer 21

Courses from the inferior medial wall of the anterior orbit to the posterior lateral aspect of the globe.

Question 22

Longest EOM

Answer 22

Superior oblique bc of its long tendon

Question 23

The superior oblique inserts where?

What angle does it form relative to the visual axis?

Answer 23

Inserts in the lateral superior posterior aspect of the globe.
Forms a 55 degree angle with the visual/Y/sagittal axis

Question 24

The inferior oblique inserts where?

What angle does it form relative to the visual axis?

Answer 24

Inserts in the lateral posterior inferior aspect of the globe.
Forms a 51 degree angle with the visual/Y/sagittal axis

Question 25

Angle that each muscle forms relative to the Y/sagittal/visual axis

1. Lateral and medial rectus
2. Superior oblique
3. Inferior oblique

Answer 25

Lateral and medial rectus- 23
Superior oblique- 55
Inferior oblique- 51