Sci-Five | The Hindu Science Quiz: On the third eyelid
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What is the third eyelid called in animals?
- Lacrimal membrane
- Nictitating membrane
- Meibomian membrane
- Macula membrane
Usually called the ‘third eyelid’, the nictitating membrane is present in some animals that can be drawn across the eye.
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What is the function of the nictitating membrane in birds?
- To protect from debris
- To protect their eyes while feeding their chicks
- To protect their eye from injury
- All of the above
In birds of prey, the membrane also serves to protect the parents’ eyes from their chicks while they are feeding them, and when peregrine falcons go into their 200-mile-per-hour (320 km/h) dives, they will blink repeatedly with their nictitating membranes to clear debris. Woodpeckers tighten their nictitating membrane a millisecond prior to their beak impacting the trunk of a tree to prevent retinal injury.
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From what does the nictitating membrane protect polar bears?
- UV rays
- The glare of sunlight reflecting from the snow
- Snowstorms
- Injury while swimming in the sea
The nictitating membrane protects the polar bears’ eyes from UV radiation as the white landscape reflects sunlight can damage the eye which can lead to temporary loss of vision — a condition known as snow blindness.
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This part of the human eye is believed to be a vestigial organ of the nictitating membrane. Name the part.
- Palmar Reflex
- Pyramidalis Muscle
- Nictitating Membrane
- Auricular Muscles
The plica semilunaris is a fold of conjunctiva at the inner corner of the human eye. Its likeness to the nictitating membrane, or third eyelid, of other animals led to the idea that it might be the vestige of such a structure, which is still part of the eye in some primates.
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What is the colour of the third eyelid found in animals?
- Transparent/Translucent
- Opaque
- Colour of the iris
- All of the above
The nictitating membrane is a transparent or translucent third eyelid present in some animals.
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