17 Things We Learned About Human Bodies In 2021 That Made Us Wonder If We Really Know Ourselves

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Vote up the facts about our bodies have you looking at yourself differently.

Humans are unique, fascinating creatures. From the amazing things human bodies can do to the ways our anatomy and physiology continue to change, it seems like there's always something new to learn about both the human form and the human condition.

In 2021, we explored specific areas of the human body like feet and came upon some interesting - if not disturbing - tidbits about our bodies, diseases, and maladies. As we poked and prodded our way to mind-blowing revelations about our bodies, we came upon information that dispelled a few myths about humans, too. Overall, what we learned made us feel a little more normal, a little weirder, and left us questioning what we see in the mirror.

Here are facts about the human form that we learned in 2021 that really stuck with us - vote up the ones that grab your attention, too. 


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    While Still In The Womb, Fetuses Can Heal Their Mothers' Damaged Organs

    Fetal cells can remain in their mothers for years, even decades after a pregnancy. These fetal cells are more than just souvenirs from the baby; research shows they can be used as an aid if the mother suffers an injury, such as a stroke. 

    Louise McCullough, director of stroke research at the University of Connecticut Health Center, conducted a study with colleagues that showed fetal cells can act like stem cells. McCullough studied fetal cells in mother mice who had suffered strokes. These cells quickly found the location of the area of the brain where the stroke had occurred, and within 72 hours, the fetal cells were surrounding the area of the clot.

  • The Heart Has Its Own 'Little Brain'
    Photo: Patrick J. Lynch / Wikimedia Commons / CC BY-SA 2.5
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    2,669 VOTES

    The Heart Has Its Own 'Little Brain'

    The heart has its own nervous system, nicknamed the "little brain" or "heart brain," that contains roughly 40,000 neurons. According to a 2019 article published in Current Pain and Headache Reports:

    Signals from the "heart brain" redirect to the medulla, hypothalamus, thalamus, and amygdala and the cerebral cortex. Thus, the heart sends more signals to the brain than vice versa.

    This intracardiac nervous system was first discovered in 1991 and is still being researched. Scientists believe it helps monitor heart health and may play a role in how the mind processes pain.

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    The Human Jaw Is Shrinking - And Has Been For Centuries

    When a 2015 scientific study announced that humans once had "an almost perfect harmony between their lower jaws and teeth," the assertion echoed what scholars had been saying for years - the human jaw is shrinking.

    In 2011, a study of more than 300 skulls indicated that, as humans became more sedentary, the resulting change in diet - from hunting and gathering to pastoral farming and processed food - caused a decrease in the amount of force required to chew. Over time, the jaw took on a new shape, which has become increasingly problematic for modern humans. 

    Due to jaw shrinkage, more and more people experience cramped teeth and, in turn, need orthodontic work. Sleep apnea and comparable sleep disturbances are also traced to the change in jaw shape.

    One consequence of shrinking jaws is the absence of wisdom teeth. As of late 2020, research indicated more humans were being born without wisdom teeth than ever before. Called a "microevolution," the lack of wisdom teeth has been attributed to "our faces getting a lot shorter... [with] not as much room because of smaller jaws." 

  • There's A Network Of Fluid In The Human Body No One Identified Until 2018
    Photo: R.J. Godlee / Wikimedia Commons / CC-BY 4.0
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    2,364 VOTES

    There's A Network Of Fluid In The Human Body No One Identified Until 2018

    Unofficially considered an organ, the interstitium was first identified in 2018. As a network of open, fluid-filled spaces, the interstitium replaced what researchers had previously thought was a "wall" of collagen.

    The interstitium exists throughout the human body, including in tissues under the skin, in the digestive and respiratory systems, and around the muscles. According to the initial study, interstitium protects the body and produces lymph, the fluid essential to immune cell function.

    While the interstitium may be new to most humans, there are indications physicians and scientists knew about it for centuries prior to its "discovery." What is new, however, is the composition of the interstitium and the possible role it has in the spread of disease

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    A Knee Bone Almost Disappeared - But It's Making A Comeback

    Medical records from 1875 indicate nearly 18% of patients had a small bone in their knee called the fabella (literally "little bean" in Latin). By 1918, that percentage decreased to nearly 11%. One century later, however, as many as 39% of patients have a fabella - but that's not necessarily a good thing.

    According to researchers at Imperial College London, the bean-like bone "just causes us problems." As a small sesamoid bone located within tendons, the fabella is present in many individuals with arthritis and inflammation in their knees.

    The bone's exact function isn't clear because, in the words of Dr. Michael Berthaume, "nobody has ever looked into it." He continued:

    The fabella may behave like other sesamoid bones to help reduce friction within tendons, redirecting muscle forces, or, as in the case of the kneecap, increase the mechanical force of that muscle. Or it could be doing nothing at all.

    The reason the bone is becoming more prevalent, as theorized by Berthaume, involves the larger composition of the human body. With taller and heavier humans, added knee pressure "could explain why fabellae are more common now than they once were."

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    Humans Have Stripes On Their Skin; You Just Can't See Them

    The stripes on humans are named for the German dermatologist who discovered them, Alfred Blaschko. In 1901, he noticed various line patterns on the skin of his patients. Generally, V-shaped lines extend over the spine; U-shaped lines are on the chest and upper arms; and S-shaped lines run across the torso. Additional perpendicular lines go up and down arms and legs, with spirals on the head. 

    Now known as Blaschko's lines, they are generally not visible to the human eye. They are visible under ultraviolet light, but emerge with greater clarity to the naked eye in the case of certain medical conditions, mostly dermatological.