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As a person ages, the elasticity of the lens
a. decreases.
b. creases.
c. remains unchanged
d. improves.
Introduction:
The eye is a three-layered, fluid filled ball divided into two chambers. The sclera forms a white capsule around the eye, except at its anterior surface where it is specialized into clear cornea. The tough, fibrous sclera serves as the insertion point for external muscles that more the eyeballs within their sockets. A portion of the underlying choroid layer is darkly pigmented to absorb light rays at the back of the eyeball. In the front, the choroid layer is specialized into the iris (the structure that gives your eyes their color), the ciliary muscle, and the zonular fibers. Circular and radial smooth muscle fibers of the iris determine the diameter of the pupil, the anterior opening that allows light into the eye. The ciliary muscles determine the shape and focusing power of the crystalline lens just behind the iris. The retina is formed from an extension of the developing brain in fetal life on which the real and inverted image is formed. The eye is divided into two fluid-filled spaces- the aqueous humor between the iris and cornea and vitreous humor between lens and the retina.
Answer to Problem 1PL
Correct answer:
The correct answer is option (a) decreases.
Explanation of Solution
Explanation/justification for the correct answer:
Option (a) decreases. When the eye needs to focus on closely placed objects, the lens needs to change its shape and increase its curvature. This activity is mediated by the ciliary muscles. With the advancement of age, the lens become tough and it becomes difficult to change the shape of the lens. This means that elasticity of the lens decreases. So, the correct answer is option (a).
Explanation for incorrect answer:
Option (b) increases. As the lens becomes tough, it will naturally become less elastic. Therefore, elasticity decreases and does not increase. So, this is an incorrect option.
Option (c) remains unchanged. With the advancement of age, the ciliary muscles become weak and lens becomes tough. Therefore, slowly the condition of the eye starts to deteriorate. So, this is an incorrect answer.
Option (d) improves. As the lens becomes tough, it will naturally become less elastic. Therefore, elasticity decreases and does not improve. So, this is an incorrect option.
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Chapter 36 Solutions
Laboratory Manual For Human Anatomy & Physiology
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