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14 Fascinating Facts About the Human Body

8. Pus is primarily white blood cells that died fighting off infection. It also consists of dead or living bacteria (or other microorganisms), and tissue debris. 

Pus
Inflamed purulent pimple with pus on human body skin close-up, health care dermatology. Image credit: Shutterstock

To fight off infection, the body sends neutrophils. These white blood cells destroy foreign bodies of fungi or bacteria. Some of these fighter neutrophils die in the process along with the surrounding tissue. The debris of the dead material is what we see and call “pus.” 

It is typically white-yellow in color but at times can be tinted brown or green. Although it’s usually odorless, certain bacteria produce foul-smelling pus.

A small quantity of pus, such as from pimples, isn’t a cause for concern, but pus at the site of a surgical incision or deep wound may require medical intervention. (1, 2)

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9. The hyoid bone is the only bone in the human body that is not connected to any other bones. It is uniquely shaped “U” and connected by only ligaments and muscles. It in fact acts as a site of attachment for many muscles in the neck.

Hyoid Bone
3d rendered medically accurate illustration of the hyoid bone. Image credit: Shutterstock

The hyoid bone’s position with relation to the muscles attached to it is likened to that of “a ship steadied as it rides when anchored fore and aft.” It’s a U-shaped structure located in the anterior neck and is connected only by muscles and ligaments, making it the only bone in the human body not connected to any other bones.

Through the muscle attachments, the hyoid plays an important role in supporting the tongue, swallowing, and voice production. (1, 2)

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10. If you pour warm water into a person’s ear, their eyes will move towards that ear, and if you pour cold water into their ear, their eyes will move in the direction of the opposite ear. This is a medical test called “caloric stimulation” and is used to test brain damage.

Caloric stimulation
Experimental design for caloric stimulation. Image credit: semanticscholar

“Caloric stimulation” is a procedure used to find damage to nerves in the ear. It involves the stimulation of the acoustic nerve by pouring cold and warm water, alternatively, into the ear canal. If the nerves are healthy, the test should cause rapid side-to-side eye movement. Along with the health of the acoustic nerve, the test also evaluates brain areas that are responsible for balance.

The test may cause some discomfort, especially when cold water is poured into the ears. It can also cause brief feelings of vertigo, leading to nausea in some people. (1, 2)

11. When you’re nervous or crying, you may realize that your throat hurts. You might also feel tightness, a lump in your throat, or have trouble swallowing. This is your body’s response to stress. It expands the glottis to provide you with more oxygen.

Throat
Sore throat. Image credit: Shutterstock

When you are anxious, the body is under a lot of stress as it releases adrenaline and cortisol. This causes the muscles to tense up. In a situation like this, the autonomic nervous system tries to fight off the stress by increasing the supply of oxygen and blood to the affected muscles.

The autonomic nervous system expands the glottis in an attempt to provide you with more oxygen. Hence, you feel a lump in your throat when you are crying or nervous.

One can tackle this problem by taking deep breaths, meditation, and drinking water. (1, 2, 3)

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12. The heart has its own “little brain,” or “intrinsic cardiac nervous system.” This “heart brain” is composed of about 40,000 neurons that are similar to the neurons in the brain. This means that the heart has its own nervous system.

Little Brain within the Heart.
The heart has its own “little brain. Image credit: Shutterstock

As is the entire body, the heart is controlled mostly by the brain. But in 1991, it was discovered that the heart has about 40,000 neurons of its own. This was labeled as the “intrinsic cardiac nervous system” (ICNS). 

The discovery changed the course of studies researching brain-heart communication. Earlier, it was based on the grounds of one-way communication with the heart only on the receiving end. The ICNS established that the heart too sends signals to the brain.

A network of neurons, this little brain adjusts the electrical and mechanical activity of the cardiac system, fine-tuning the heart’s rhythm. The neurons are located at the top of the heart in the form of clusters and are present in abundance on the left side. (1, 2, 3)

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13. Children have more energy than well-trained endurance athletes. They have muscles that are resistant to fatigue, and they also recover faster than both untrained and trained adults. 

Children more active than adults
Children have more energy than well-trained endurance athletes. Image credits: Shutterstock, Shutterstock

In a study published in 2018, it was documented that prepubescent children have energy levels that can beat that of even a well-trained athlete. 

Their fatigue-resistant muscles are the reason children seem to play for long without getting tired. The study also found that the young participants recovered faster than their adult counterparts.

However, their aerobic fitness decreases significantly once they move into adulthood. (1, 2)

14. Owing to evolution, the fabella, a small bone behind the knee, disappeared from the human body. Unexplainably, it is making a comeback. It was found in 39% of the population in 2018 as compared to only 11% in 1918.

Fabella
Tiny knee bone (fabella), once lost in humans, is making a comeback. Image credit: imperial

Typically, the human body contains 206 bones. But sometimes, the number can be 208. 

A small bone, called the “fabella,” located in a tendon behind the knee, vanished from our lineage during early human evolution.

Mysteriously enough, it has made a comeback and is becoming more common. Historically, the bone was found in only 11% of the world population. However, in 2018, it was found in 39% of the population.

Though the bone’s function is unknown, it seems to be of use in knee muscle mechanics in old-world monkeys. (source)

Also read: 10 Biggest Basic Design Flaws in the Human Body

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