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Anatomy and function of the superior oblique muscle.
Hi everyone! This is Matt from Kenhub, and in this tutorial, we will be looking at the superior oblique muscle of the eye. We will look at its origin and insertion, function, innervation, and blood supply.
There are six extraocular muscles that control the movements of the eye – four rectus muscles and two oblique muscles. The superior oblique muscle, shown in green, is one of these oblique extraocular muscles, meaning it isn’t straight like a rectus muscle but instead attaches to the eye in a less direct, more oblique way which influences the eye movements it is responsible for.
The superior oblique muscle originates from the common tendinous ring, also known as the annulus of Zinn, which is located at the apex of the orbit around the orbital canal here. The annulus of Zinn is formed by the tendons of the extraocular muscles.
For its insertion, the tendon of the superior oblique muscle passes through the trochlea, in green, and approaches the sclera – the white of the eye – obliquely from the medial margin of the orbit. The superior oblique inserts onto the posterior superior lateral surface of the eye.
When the eye is in a neutral position, the superior oblique muscle is responsible for abduction which is movement of the eye laterally away from the nose, intorsion which is inward medial rotation, and depression which is movement of the eye inferiorly. Depression of the eye by the superior oblique muscle is most effective when the eye is in an adducted position.
The superior oblique muscle also helps to provide the eye with more stability by counteracting head movements to prevent involuntary rotation of the eye.
Innervation of the superior oblique muscle is provided by the fourth cranial nerve – the trochlear nerve. This is the only extraocular muscle to receive innervation from the trochlear nerve. It can be seen innervating the superior oblique muscle here.
The blood supply to the superior oblique muscle comes from two branches of the anterior ciliary arteries which are derived from the ophthalmic artery in green.