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Don't worry, this material won't be asked in the quiz ! But it is still definitely worth knowing... |
The rectus muscles insert in sclera gradually farther from the limbus beginning with the medial rectus at 5.5mm (range 3.0 to 6.0mm), inferior rectus 6.5mm, lateral rectus 6.9mm and superior rectus 7.7mm. The line of insertion is called the Spiral of Tillaux which is also the line of insertion of posterior tenon’s capsule . |
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Each of the rectus muscles has two anterior ciliary arteries except the lateral, which has only one. A long posterior ciliary artery travels from the back of the eye in sclera beneath the horozontal recti. The oblique muscles do not contribute to the blood supply of the anterior segment of the eye. |
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The Superior Oblique (S.O.) is made up of a 30mm muscle, and 30mm tendon with the trochlea between. The S.O. has its functional origin in the trochlea. This unique structure allows an 8mm increase in the trochlear insertion distance in upgaze and an 8mm decrease in distance between the S.O. insertion and trochlea in downgaze. |
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The inferior oblique originates at the posterior crest of the lacrimal fossa medially and inserts at the lower border of the lateral rectus 12mm posterior to the lateral rectus insertion. |
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The origin of the rectus muscles is the Annulus of Zinn, in the posterior aspect of the orbit. Superior oblique originates here too.The rectus muscles are each 40mm long. They receive innervation on the global surface at the junction of the middle and posterior 1/3 of the muscle. The pulleys are located on the orbital surface at the junction of the middle and posterior 1/3 of the globe. |
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The pulley-like structure at the level of the junction of the middle and posterior 1/3 of the globe of the horizontal recti are fibro-muscular structures which behave as a functional origin. |
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