EOM's Flashcards
Define origin and insertion
Origin- fixed attachment
Insertion- Moves with contraction
Origin of the 4 rectus muscles
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.
The common tendinous ring is divided into which 2 thickened bands
What bands do the 4 recti muscles attach to?
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
Which two recti muscles attach to the common tendinous ring and also the dural sheath of the ON?
The superior rectus and medial rectus.
Which recti muscle attaches to a prominence on the greater wing of the sphenoid?
The lateral rectus. Connects to the spina recti lateralis.
Course of the medial rectus
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.
Course of the lateral rectus
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.
Course of the superior rectus
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.
Course of the inferior rectus
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.
Recti muscles become ___ prior to their insertions.
They penetrate ___ in order to attach to sclera
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.
Medial rectus inserts where?
Which axis is it parallel to?
Inserts anteriorly and medially.
Parallel to the sagittal/visual/Y axis
The lateral rectus inserts where?
Which axis is it parallel to?
The lateral rectus inserts anteriorly and laterally.
Parallel to the sagittal/visual/Y axis
The superior rectus inserts where?
What angle does it form relative to the visual axis?
It inserts in the lateral, anterior, superior aspect of the globe.
What angle does it form relative to the visual axis?
The inferior rectus inserts where?
What angle does it form relative to the visual axis?
The inferior rectus inserts in the lateral, anterior, inferior aspect of the globe.
What angle does it form relative to the visual axis?
Muscle insertion to limbus distance
Medial rectus is the most anterior: 5.5mm
Inferior rectus: 6.5mm
Lateral rectus: 6.9mm
Superior rectus is the most posterior: 7.7
What is the spiral of Tillaux
Muscle insertions to limbus forms a spiral of most anterior at the medial rectus to the most posterior at the superior rectus
The superior oblique muscle originates where (2)
Originates at the lesser wing of the sphenoid bone just above the optic canal at the orbital apex.
Functional origin is at the trochlea
Origin of the inferior oblique
Originates at the maxillary bone. Just posterior to the inferior medial orbital rim of the maxillary bone.
Which is the only EOM to have origin in the anterior orbit?
The inferior oblique
Course of the superior oblique muscle
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.
Course of the inferior oblique muscle
Courses from the inferior medial wall of the anterior orbit to the posterior lateral aspect of the globe.
Longest EOM
Superior oblique bc of its long tendon
The superior oblique inserts where?
What angle does it form relative to the visual axis?
Inserts in the lateral superior posterior aspect of the globe.
Forms a 55 degree angle with the visual/Y/sagittal axis
The inferior oblique inserts where?
What angle does it form relative to the visual axis?
Inserts in the lateral posterior inferior aspect of the globe.
Forms a 51 degree angle with the visual/Y/sagittal axis
Angle that each muscle forms relative to the Y/sagittal/visual axis
- Lateral and medial rectus
- Superior oblique
- Inferior oblique
Lateral and medial rectus- 23
Superior oblique- 55
Inferior oblique- 51
