Medialis rectus muscle (Mrm)
The medialis rectus muscle is a sheet-like muscle composed of thin parallel fibers located at the nasal pole of the eyeball, entirely covered by the dorsalis oblique muscle and the Harderian gland. It originates from fleshy fibers of the orbitosphenoid bone. These muscle fibers turn obliquely towards the medial surface of the eyeball to insert into the scleral cartilage, which is positioned inferior to the Harderian gland\RL.
Origin: Fleshly, from the orbitosphenoid bone\RL.
Insertion: Aponeurotic, on the scleral cartilage\RL.
Function: Pulls the eyeball towards the anterior nasal pole (adduction).