6 During pregnancy, the volume of blood pumped by the heart in the pregnant woman can rise up to 50%. The increase happens to provide more blood to the uterus when the fetus grows.

A woman goes through a wide array of changes during pregnancy, and these changes are often quite demanding. The heart does all the extra work to provide blood to the uterus.

The volume of blood supply rises by 30% to 50% during pregnancy, and by the end of the pregnancy, the uterus demands one-fifth of the blood supply in the pregnant woman’s body.

The increase in the volume of blood is surprisingly marked by a greater increase in the number of fluids and white blood cells as compared to the increase in the red blood cells.

Cardiac exercises increase and so do heart rates during pregnancy. It rises from 70 to 90 beats per minute, and during labor, it further increases by 30%.

As the amount of blood supply increases, the kidneys, too, now need to work harder to filter the extra blood. (source)

7 Humans are bioluminescent, meaning we emit our own light that glows in the dark, but it is not visible because the light that we emit is a thousand times weaker than our eyes can pick up. 

Generally, deep-sea creatures are the ones that have this ability to emit their own light. Astonishing studies in 2009 by Japanese researchers from Tohoku Institute of Technology found that we are bioluminescent too.  

The conclusion was made by the team after observing five healthy males through super-sensitive cameras for 20 minutes every three hours for three days inside a light-tight room during sleep. 

The brightest spots they observed were on the forehead, neck, and cheeks, and they also found that the light was dimmest late at night. 

The invisible, weak light is actually a by-product of a biochemical reaction that involves free radicals. (1, 2)

8 The intestines in our body are always in a near-constant motion, a wave-like or wiggling motion to facilitate the digestive processes. It becomes a terrible condition if the motion stops because it can create food blockages in the intestine that can be life-threatening. 

The continuous muscle motion is called “peristalsis,” and its primary objective is to push the food material downward and through the intestines. 

The wave-like motions are weaker and the intensity progressively grows as we move farther from the stomach. Not the entire intestine is always in motion. About three waves happen each minute in different regions.

If for any reason this motion stops, it creates a jam in your intestine and poses several health problems. The condition in which the motion is stopped is called “ileus,” and it can be caused by any nerve or muscle problem in the intestine. 

Ileus can then further cause intestinal obstruction in which the intestine does not let any gas, food material, or liquids go through them. 

Ileus is a serious condition and can be life-threatening as it can literally tear up the intestinal tissues. (1, 2)

9 A heart does not need a body to beat as long as it receives an oxygenated blood supply. This means, if it has a steady supply, it will just go on with or without the owner. This also explains why the heart continues to beat for a brief amount of time after brain death or after removing it from the body. 

The heart does not even need a body or in fact a brain to keep working because it has its own electrical system to rely on. It is not arguable that our brain controls the dynamics of our heart, but the beating of the heart and pumping of the blood is purely independent.

The heartbeats are facilitated by the inbuilt pacemaker inside the heart itself. If this wouldn’t have been the case, your brain would have to send a signal to trigger every single heartbeat, and that’s pretty inefficient. 

The heart usually survives in an icebox for up to four hours after being removed from the body, but technology has surely increased this duration, too. (1, 2)

10 Oddly, we are the only species with chins. Even our closest genetic species like gorillas and chimps don’t have them, and also our ancestors, the hominids, didn’t either. The reason why we have the chins still remains an evolutionary mystery. 

For scientists and other researchers too, it is a huge question mark of why only humans have chins. It has bedeviled the researchers for the last century, and yet there are no absolute explanations and theories around the subject. 

If we study the family tree of evolution after we split from the chimpanzees, all we have are hominids. Now across all hominid species, there are not many traits that are exclusive to humans such as all of them walked on two legs. However, the chin stands out as an exception and has no real answer yet.

One of the common narratives is that we have chins to support ourselves while chewing food. Still, the theory is disputable. 

Other notions involve completely eradicating any use of the chins. Such a theory claims that it is just a by-product of other features’ evolution and has no real purpose. This theory has its shortcomings too.

Another idea says that it has been developed for us to select sexual mates. But sexually selective features have always been gender-specific, so that cuts it out as well. (1, 2)