Week 1 - Inferior Rectus

Question 1

What is the origin of the inferior rectus

Answer 1

It is at the annulus of Zinn at the apex of orbit

Question 2

What is the course of this muscle

Answer 2

It follows the orbital floor

Question 3

Where does this muscle insert

Answer 3

The inferior rectors insert on the underside of the eye in front of the centre of rotation at an angle just like a superior rectus

Question 4

Which nerve supply is this muscle

Answer 4

It is the inferior division of the third cranial nerve i.e. the oculomotor nerve

Question 5

What is the primary and secondary action of the inferior rectus

Answer 5

Primary action; when the inferior rectus contract and polls, the eye is pulled down so the primary action is depression – this is because the muscle is at an angle

The secondary action of the superior rectus is extortion – it turns the eye in and because this muscle is under the eye also twist the eye and Pulls eye outwards