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Which of the following represents correct matching set of part of human eye and its function? a Cornea (i) Controls the amount of light entering eye b Iris (ii) Acts as screen for the image c  Pupil (iii)  Holds the lens in positions d Retina (iv) Helps in focusing light and protects eye e Ciliary Muscle (v) Light enters eye through it

Which of the following represents correct matching set of part of human eye and its function? a Cornea (i) Controls the amount of light entering eye b Iris (ii) Acts as screen for the image c  Pupil (iii)  Holds the lens in positions d Retina (iv) Helps in focusing light and protects eye e Ciliary Muscle (v) Light enters eye through it Correct Answer a - (iv), b - (i), c - (v), d - (ii), e - (iii)

The correct answer is a - (iv), b - (i), c - (v), d - (ii), e - (iii).

Concept:

  • The human eye is one of the most valuable and sensitive sense organs.
  • It enables us to see the wonderful world and the colors around us. On closing the eyes, we can identify objects to some extent by their smell, taste, sound they make, or by touch.
  • It is, however, impossible to identify colors while closing the eyes. Thus, of all the sense organs, the human eye is the most significant one as it enables us to see the beautiful, colourful world around us.

Explanation:

Parts of an eye:
The adult human eyeball is nearly spherical in structure. It consists of tissues present in three concentric layers
i) Outermost fibrous layer composed of sclera and cornea.
ii) Middle layer consists of choroid, ciliary muscles and iris.
iii) Innermost layer consists of retina

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Outermost layer-

  • Sclera:
    • It is an opaque outermost layer, composed of dense connective tissue that maintains the shape of the eyeball and protects all the inner layers of the eyeball.
  • Cornea:
    • The cornea is a thin transparent, front part of sclera, which lacks blood vessels, but is rich in nerve endings. These nerve endings are in charge of the involuntary reflex of closing the eyelid in response to touch, preventing foreign particles from entering and causing damage to the eye.
    • The cornea and lens work together to help in focusing light rays on the back of the eye.

Middle layer-

Choroid:

  • It is a pigmented layer (bluish) present beneath the sclera. It contains numerous blood vessels and nourishes the sclera.
  • The choroid layer is thin over the posterior two-thirds of the eyeball, but it becomes, thick in the anterior part to form the ciliary muscles.

Ciliary muscles:

  • Ciliary muscles holds the lens in position, stretching and relaxation of ciliary muscles changes the focal length of the lens for accommodation.

Iris:

  • Iris forms a pigmented circle of muscular diaphragm attached to the ciliary body in front of the lens.
  • The pigment present in it gives characterstic colour to the eyes.
  • Iris controls the amount of light that enters the eye by adjusting its size. The iris is a thin membrane that controls the pupil, which in turn controls the amount of light that enters the eye.

Pupil:

  • It is the aperture surrounded by the iris.
  • The cornea bends light rays so that they pass freely through the pupil, which allows light into the eye.

Innermost layer

  • Retina:
    • The retina is a delicate membrane having enormous
    • number of light-sensitive cells. 
    • The light-sensitive cells get activated upon illumination and generate electrical signals.
    • Retina acts as screen for the image.
a Cornea (iv)

Helps in focusing light and protects eye 
b Iris (i)

Controls the amount of light entering eye 
c  Pupil (v) 

Light enters eye through it
d Retina (ii)

Acts as screen for the image
e Ciliary Muscle (iii) Holds the lens in positions

Related Questions

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1. Ciliary muscles attached to the lens
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2. Ciliary muscles attached to the lens thicken for closer objects
3. Ciliary muscles flatten the lens for closer objects
4. Ciliary muscles thicken the lens for distant objects
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 Which of the following statements is/are true of the human eye lens? Choose the correct answer from the code given below:  (i) It is a convex lens (ii) It is a concave lens (iii) It is a convex lens of variable focal length (iv) It forms a real and inverted image of a distant object at the retina
Find the missing term in the following series? Cornea, Iris, Pupil, Lens, ?