Table of contents:
99% of the calcium in the human body is contained in teeth.
The strongest muscle in the human body is the tongue.
Bones are about 5 times stronger than steel.
Have you ever heard about the myth that if you sneeze with your eyes open, they will pop out? Well, not surprisingly, that's a lie. Here's a compilation of some less-known, interesting and surprising facts about the human body that will amaze you!
1 - Your feet are the same length as your forearms.
"The whole length of the foot will lie between the elbow and the wrist." These words can be found in one of Leonardo da Vinci's notebooks, dated back to XIV century. Da Vinci was well known for his studies of the human body, including detailed measurements such as this one! If you don't believe it, check for yourself!
2 - Your DNA is so long it could cover the distance from the Sun to Pluto and back.
DNA or deoxyribonucleic acid is a molecule that carries the genetic information within the cells of the human body, making it the hereditary material of the body cells. DNA consists of long chains of nucleotides, which successively coil spirally around another, which makes them extremely compact on chromosomes. The total length of all the DNA in a single cell's nucleus is astonishing 6 feet! If you stretched out your entire body's DNA, it would be about twice the diameter of the Solar System.
3 - The lining of your stomach turns red when you blush
Blushing is governed by the sympathetic nervous system; therefore, we blush when feeling shy, ashamed or embarrassed. It is the reddening of your face as a natural response to either physiological or psychological factor, which causes our body to release adrenaline, a hormone that prepares the body for stressful situations. Adrenaline makes the blood vessels dilate (vasodilation) order to improve blood flow and oxygen delivery in case of danger. When there's more blood flowing through the veins in your face, as well as in your stomach lining and throughout the rest of the body, it makes them appear red. Some people can even experience blushing on their neck, ears, and arms.
4 - Your right lung takes in more air than your left lung.
Lungs are one of the largest organs in your body. As some of you may know, our lungs are not of the same size – your right lung is a bigger than your left lung, which has to share space with your heart. Because of this, the right lung consists of three lobes (superior, middle, and inferior), whereas the left lung has only two (superior and inferior). Therefore the volume of air taken in by them will always differ.
5 - Astronauts grow taller in space.
NASA used ultrasound technology to investigate what happens to astronauts' spines in microgravity. According to them, astronauts who return from a space mission can be even 3 inches (or 7 centimetres) taller than they were before their departure. This is because the bones in our spine (vertebrae) expand and relax when exposed to less gravity pushing down on them. Unfortunately, the astronauts go back to their normal height after a few months upon their arrival. We could compare this phenomenon to something we do every night – lying in bed. Our spine relaxes, therefore expands, and after we get up, we gradually go back to our usual height.
6 - You can't taste food until it's mixed with your saliva.
To taste the food, chemoreceptors in the taste buds of your tongue require liquid. This is because they function by reacting with molecular chemical compounds in a substance. Without a liquid medium, everything would be tasteless. You can see yourself by drying your tongue with a kitchen towel and putting food on your tongue right afterwards – you won't be able to taste anything until your body starts producing saliva again.
7 - Our eyes see images upside down.
This does not mean that the world is upside down though! The light refraction physics causes the upside-down impression on the retina in your eyes. Your brain, however, takes this inverted image and turns it right-side-up. It is believed that for the first few days, babies see everything upside-down. This is because their vision is still at development stage at this point, and also their brain isn't used to performing image conversion yet. You can easily verify this yourself by gently pressing the bottom right side of your eyeball through your bottom eyelid - a black spot appears at the top left side of your vision, proving that the image has been converted.
8 - Hyoid – the only bone that isn't connected to other bones in your body.
Hyoid, also called lingual or tongue bone, is a small bone in your throat, connected only by ligaments and muscles that sustain it beneath the tongue - it works almost like an anchor for your tongue! The hyoid bone is connected to your body by six muscles located above it, and three that are below it. Altogether with the larynx, which is your body's voice box, hyoid allows us to speak.
9 - Your liver has over 500 functions.
When you think of what your liver does, the first thing that comes to mind is probably alcohol metabolization. But this is not the only function of this crucial organ in your body – in fact, it has over 500 different functions, including, e.g., controlling of fat levels, amino acids and glucose in your blood, production of cholesterol, processing digested food and turning it into energy, and many, many more. It also creates enzymes that play a crucial role in various chemical reactions, like regulating blood clogs and fixing broken tissue.
10 - Reading about yawning makes you yawn.
Yawning is a natural reaction to keep yourself awake. It is triggered by boredom, tiredness, and temperature. Everybody yawns, no matter the age, and in fact, you've been yawning before you were even born! And there are high chances that you have probably yawned at this point. But why is yawning so contagious? This phenomenon is a reaction to reading, seeing, hearing or thinking about yawning, it is unconscious, meaning we have no control over it. It is only observed in humans and chimps. Scientists believed that this reaction could be related to empathy, however, this theory has been recently disproved. And even so, it is still not known why contagious yawning happens – it appears to be a scientific mystery.