Week 1 - Medial Rectus Flashcards
What is the origin of the medial rectus
The origin of the medial rectus is at the annulus of zinn at the apex of the orbit
What is the annulus of zinn
It is a ring of fibrous tissues surrounding the optic nerve at the entrance
it is the common origin of the four rectus muscle is
What is the course or pathway of the medial rectus
The MR starts at the back of the orbit at the annulus of zinn
The MR runs up the medial side of the orbit and follows the orbital wall
When does muscle gets shorter and contracts it pools of the eye in that direction this is known as adduction (meaning pulling something towards the nose)
Where does the MR insert
This muscle insert into the sclera in front of the centre of rotation of the eye on the nasal side
The MR attaches closest to the front of the eye more than any of the other five muscles and it has the mechanical advantage of being able to turn the eye more in then out
What is the nerve supply of the medial rectus
The third cranial nerve, oculomotor nerve (more specifically the inferior division) supplies this muscle
What is the primary and secondary actions of the medial rectus
Primary: the primary action of the MR is poor adduction i.e. pulling the eye in towards the nose
Is the eye is in a primary position when the MR contracts , it pulls the eye towards the nose and this is it only action
There is no secondary action the only thing this muscle does is Pull the eye to the nose
