Can Your Eyes Breathe?

By Anupum Pant

Wait! Who says eyes breathe

The transparent front part of the eye that covers the iris and pupil is called Cornea. Cornea contributes a lot to the focusing power of the eye. That means, light has to pass through it without obstruction. To do that it has to remain completely clear. Consequently, to remain transparent, it can’t have any impurities nor can it have any blood vessels – that would have made it less transparent.

Every organ needs oxygen to run the cell processes with the energy that comes by oxidizing nutrients contained in the cells. To receive oxygen, they need to have access to blood. Since Cornea does not have any blood vessels, it cannot receive oxygen from blood. So what does it do to stay alive?

It absorbs oxygen directly from the air through diffusion. Oxygen gets dissolved in the tears and then diffuses across the cornea. However, the amount of diffused oxygen is so less that it is just enough for only the cornea cells. This can’t be supplied to other parts of the body. And this is exactly the reason you would get yourself killed if you plug your nose and your mouth, expecting your eye would keep you alive by breathing in oxygen.

In a sense, you could call it breathing. But it isn’t exactly ‘breathing’. Breathing, according to the medical definition means:

The process of respiration, during which air is inhaled into the lungs through the mouth or nose due to muscle contraction and then exhaled due to muscle relaxation.

Clearly, as the oxygen received by cornea doesn’t come from the mouth or nose and never goes through the lungs, it cannot be called breathing.

Other ways?

Let us consider the second possibility. At the inner corner of the eye there is a very thin tube that connects to the nose. Through this tube (A.K.A the Punctum), your eye is able to drain off excess tears. Punctum is the reason, you have to blow your nose when you cry. Punctum is also the tube that enables this guy to squirt milk out of his eyes (By sucking it through his nose first) [Video – Pretty disgusting to watch]

Also, you can blow an extremely tiny volume air out of these corner eye holes. But, you can’t breathe in through them.


Although the cornea of your eye has the ability to absorb oxygen directly from the air, you cannot technically call it breathing.


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A Bat’s Inverted Sleep Position

by Anupum Pant

I have written about sloths in the past. In that post, we appreciated the way their bodies are engineered to stay inverted for most of their lives. It turns out, a bat’s body is designed (rather evolved) in a similar way, which enables them to relax and sleep upside down. In this post, I would like to discuss – why did they evolve this way and how do they do it?

If you are interested to know more about bats, you will definitely like this post from the archives. [Bats can See]

How can bats manage to sleep like this?

Humans sleep in a horizontal position, cows sleep with their eyes open, horses sleep in a standing position, and of course, bats sleep in an inverted position. What makes an animal sleep in the position they do, is basically their anatomy – the way their bodies are designed. While sleeping upside down might seem as an anomalous behavior to us, it is a normal position for the bat’s body. Like we don’t exert energy when we are lying down, bats’ bodies don’t consume extra energy for hanging down like that.

Firstly, a bat’s claw is like a hook. A better way to understand why this helps is, to look at a converse behavior – the way a human hand works. We use up energy to contract tens of muscles and make up a hook with our fingers; this is not a normal state of our hand. Also, our relaxed hands are open where we don’t exert any energy and we sleep with our hands in that position. A bat’s claws are designed in a completely inverse fashion; they are hooked in the normal position. They don’t take up energy to make them into hooks, they are like that. And they sleep like that – which enables them to hang without using energy.
So, unlike our hands, a bats’ closed fist is their relaxed position. They have to contract tendons and use energy to open them up. This anomalous talon design allows them to hang in a relaxed position.

Bat's Talons - Normal position

Secondly, unlike every other bird, a bat can’t take off from an upright position, or from the ground. They have to be inverted to start flying. This is because they have relatively weaker wings which can’t make them fly from a stationary position. Think of an X-51A Waverider, which has to be carried on a B-52 plane and dropped down to start a flight. They drop down for a very small amount of time and beat their wings vigorously to start a flight. Since, they have to wake up inverted to go flying and catch a meal, they go to sleep like that.

Why did they evolve this way?

They’ve evolved this way to simply stay away from the predators:

  1. By hiding up in a place where not many predators would look – under a bridge, roof of the cave and dark tree canopies. Also, at places like these, they don’t have to compete with other birds for a place.
  2. And by escaping quickly in case of an attack by attaining instant flight [see above].