The cornea is the outermost part of the eye and it is responsible for most of the light refraction in the eye (the bending of light rays). On the periphery of the cornea is the sclera which helps maintain eye shape. The space behind the cornea is the anterior cavity which is found in front of the lens. It is composed of two smaller chambers, the anterior chamber and the posterior chamber. The anterior chamber is between the cornea and the iris, the part that determines eye color. The posterior chamber is between the iris and the lens. The lens is made of protein and is held to the wall of the eye by the suspensory ligaments. These ligaments are pulled by the ciliary muscle on the wall of the eye. When the ligaments tighten, the lens flattens and the eye focuses on distant objects. The fluid in the anterior cavity is known as aqueous humor and it is released by the ciliary body and reabsorbed in the scleral venous sinus.
Behind the lens is the posterior cavity. This cavity is filled with a jellylike material called vitreous humor. Light travels through this medium to the back of the eye where it strikes the retina. The retina is the region of the eye where light waves are converted to nerve impulses. The fovea is a small area of the retina where there is a high concentration of cones (cells that determine color and visual acuity.) Behind the retina is the choroid, a darkened layer that absorbs light, making vision sharp during the daytime. Behind this layer is the sclera, the white of the eye, where muscles attach. At the posterior of the eye you can see the optic disk. This is where the optic nerve takes visual impulses from the eye to the brain. Color the median section of the eye after you have filled in the appropriate labels.
Answer Key: a. Scleral venous sinus , b. Ciliary muscle, c. Retina, d. Choroid, e. Fovea, f. Optic nerve, g. Optic disk, h. Sclera, i. Posterior chamber, j. Anterior chamber, k. Cornea, I. Lens, m. Iris, n. Suspensory ligament, o. Anterior cavity, p. Posterior cavity, q. Vitreous humor kaplan*-» _ ice
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.