17. Answer briefly III

a. Iris is a ring-shaped structure located behind the Scleracornea. The colour of human eyes are based on the  pigmentslight in the iris. The main function of the iris is to control the size of the pupilprotects the inner parts of the eye based on the light entering to eye.

 

b. The small opening which allows light to enter the eyes is called conjunctivapupil.

 

c. LensCornea is a biconvex, adjustable crystalline part of the eye, which is made of proteinslipids.

 

d. ScleraRetina is the light-sensitive part, which consists of the photoreceptors called rods and cones, helps us to visualize the different types of images. It converts the chemical energy into light energylight into electric impulses, which travels to the brain by the path of nerves called the olfactory Nerveoptic nerve.