Question

Aperture of the pupil is controlled by
(a)Conjunctiva
(b)Cornea
(c)Iris
(d)Retina

Answer 1

Hint: It is a thin layer present in the eye that is also responsible for giving the color to the eyeball. It controls the size of the pupil depending upon the amount of light entering the eye. It is also called the diaphragm.

Complete answer:
Iris is the opaque layer that is responsible for controlling the aperture of the pupil of the eye. It also gives various colors to different eyes and also helps in changing and adjusting the size of the pupils according to the light available.

Additional Information:
-Iris is the thin, outer, and opaque layer that covers the pupil and protects it.
-The iris itself is composed of two layers
 (a)Stroma - It is made up of fibrovascular layers and contains pigments.
  (b)Epithelial cells - They are present below the stroma and are also pigmented.
-The sphincter muscles are present in the stroma region and they are responsible for the contraction of pupils in a circular motion.
- The stroma also consists of dilator muscles that are responsible for the radial elongation of the irises and the pupil and then pulls the pupils in various folds.
-The inner circular sphincter muscles when starts contracting and dilating then it will result in the change in the size of the pupil. The outer part of the iris does not rotate nor change the size.
-The epithelium cells are pigmented that is located in the backside of the iris while epithelium cells are absent in the front part of the iris.
So, the correct answer is ‘Iris’.

Note: The conjunctiva is the thin layer that surrounds the eyelids and its main function is the protection of the eye mainly the cornea. The cornea is the inner part of the eye from where the light enters and also absorbs oxygen from the air. The retina is a layer of nervous tissue that covers the back two-thirds of the inside of the eyeball, in which stimulation by light occurs, initiating the sensation of vision. The retina is an extension of the brain nerve and is connected to the brain by the optic nerve.