Book of the Ten Treatises of the Eye the sclera, a thick, hard membrane which protects the inner parts of the nerves from injury. The chorioid, a thin and soft structure filled with veins and arteries, follows next and provides nourishment to the overall structure. Finally, the retina transmits nutrients to the lenses themselves. Hunayn then presents the system responsible for protecting the eye. From the outermost level, these are the conjunctiva, cornea, and uvea. While both the conjuctiva and cornea provide protection with minimizing hindrance to the lenses, the uvea has an extra function of concentrating the pneuma exiting out of the eye to prevent it from
Long posterior ciliary arteries Long posterior ciliary arteries The long posterior ciliary arteries are arteries of the head arising, together with the other ciliary arteries, from the ophthalmic artery. There are two in each eye. They pierce the posterior part of the sclera at some little distance from the optic nerve, and run forward, along either side of the eyeball, between the sclera and choroid, to the ciliary muscle, where they divide into two branches. These form an arterial circle, the circulus arteriosus major, around the circumference of the iris, from which numerous converging branches run, in the substance of the iris, to its