Why do we yawn? And four other bodily functions explained

Are you yawning yet? Thought so.

Infectious yawns are as frustrating as they are intriguing. Sometimes it's enough to need to see someone yawn, hear them talk about it or even read about it for you to suddenly get the uncontrollable urge to yawn yourself.

Man yawning looking at his phone
In 1888, a doctor reported a patient having a bout of yawning that lasted five weeks. Now that would be tiring.

We’re excruciatingly aware that this happens (it can be very embarrassing to not be able to stop yourself from displaying the back of your throat), but have you ever thought about why? We’ve taken a look at yawning, and some of the other weird things our bodies do on a daily basis.

Why do we yawn?

One theory you may have heard of is that yawning aids your breathing, in that it allows more oxygen to enter your body, expelling excess carbon dioxide in the process.

However, a number of experiments were run to test this theory in the 1980s, and all of them concluded that this is entirely false. So why do we do it then?

Well, new research suggests it might be because yawning cools the brain down and prevents it from overheating, much like the fan in your laptop. Yawning is sometimes associated with fatigue, and given that you’re more likely to feel drowsy in warm temperatures, the links appeared to make sense. Some tests have been done to try to prove this theory, but so far the evidence is a bit more anecdotal than rooted in hard data, so the jury’s still out.

As for contagious yawning, it’s thought that it could be a really old form of communication. This is because, again, it’s associated with tiredness, so the theory goes that it would signal that to everyone around them and so their body clocks would sync.

Why do our tummies rumble?

Funnily enough, it’s not actually your stomach that growls when you’re ravenous. When you digest food, your intestines contract to move the food you’ve eaten through them in a process called peristalsis. When there’s a lot of air trapped in them, the contractions causes the air to make the rumbling sound we know and love, or borborygmus to give it its scientific name.

Its links to hunger are debated, but it’s thought that when you’re Hank Marvin, hormone-like substances get released that activate the parts of your body that want you to eat, so this sends signals to your stomach and intestines and... voilà, borborygmus!

Man holding his stomach
It’s the last thing you want to hear in the middle of class or a meeting.

Why do we fart?

You might want to hold your nose for this one. People fart on average between 5-15 times a day, but it’s comforting to know that this sometimes smelly process ultimately has a good purpose.

When you eat and drink, it’s not just a delicious meal you’re swallowing - you’re also taking some air down with it too. Along with the oxygen and nitrogen you swallow, more gases are formed when your food is digested - like hydrogen, methane, and hydrogen sulphide.

Some of these gases are naturally absorbed by your body, but the rest has to go somewhere, so voilà! A fart is born. Sulphur is the smelliest of these gases so if your flatulence is particularly potent, you have sulphur to blame. Red meat and dairy are particularly high in sulphur so if you want sweet-smelling flatulence, you might want to avoid those.

However, if your farts are smelling worse than usual or you’re farting more than you normally would, this could mean you are poorly, so make sure to see a doctor.

Why do we blink?

It’s widely agreed that we blink because we need to keep our eyes moist. When our eyes are open, the tears that usually covers the surface starts to evaporate, and if our eyes are dry it can be really painful, so blinking helps top up the fluid. It’s also an effective method of keeping out other irritants, like dust and really bright light.

However, we blink on average about every three or four seconds, and some scientists believe that this is far more often than necessary to keep our eyes wet. So why else might we do it?

Studies done at Osaka University in Japan found that it might help us mentally refresh, by giving us a micro-break every so often. It’s almost like having a really tiny sleep, all throughout the day.

Why do we sneeze?

Woman sneezing
You can’t help but close your eyes when you sneeze - it’s an involuntary reflex.

On average we sneeze about four times a day, but as hayfever-sufferers will know, there are days when it feels like we’ll never stop sneezing.

So what are we actually doing when we sneeze? Well, it’s essentially to get rid of any nasty stuff that shouldn’t be in your nose. The inside of your nostrils contain sensors that raise the alarm when anything gets inside that shouldn’t, and this triggers tiny hairs called cilia to move in order to brush it away. If you have a sneezing fit with multiple in a row, it’s because your nose is making sure that everything has definitely been cleared out.

Cilia needs mucus to work and so our body produces about a litre of the disgusting stuff every day, most of which we swallow. Ew.

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