Bursalis muscle (Bm)
fibers, appearing as a derivative of the retractor bulbi muscle. It
originates from fleshy, narrow fibers of the parabasisphenoid bone,
spreading out to form an aponeurosis that inserts into the scleral
cartilage. The origin site of the bursalis muscle is ventral to the
optic nerve and posterior to the origin site of the retractor bulbi
muscle. Its insertion site is ventral to the insertion site of the
lateralis rectus muscle. The tendon of the bursalis muscle runs
anterodorsally toward the upper eyelid and anteroventrally toward the
lower eyelid\RL.
Origin: Fleshly, from the parabasisphenoid bone\RL.
Insertion: Aponeurotic, on the scleral cartilage\RL.
Function: Pulls the eyeball inward and outward within the
socket.