10 Extraordinary Facts About the Human Body
Millions of years of evolution have given the human body various abilities, mental and biological, voluntary and involuntary, not just to survive but also to thrive. Though there are various other life forms on this planet with amazing capabilities, humans have gained an edge over them especially because of their ability to conceive new ideas and create new things. Here are some extraordinary facts about the human body we’re sure you’ll enjoy reading about.
1 Humans are the best endurance runners among all running animals. Given long enough distances, they can outrun any animal on Earth.
According to Harvard’s anthropology professor Daniel Lieberman, “Humans are terrible athletes in terms of power and speed, but we’re phenomenal at slow and steady.” Unlike other species of mammals, humans evolved to be bipeds two to three million years ago. Humans used persistence hunting. That means they would run, walk, and track game animals over long distances gaining an advantage over other carnivores. Also, unlike all other animals, humans participate in marathons voluntarily. Even the best of distance runners in animals, like horses or dogs, only do so if forced, though humans are far better at it.
Humans are better endurance runners because of their center of mass and ability to sweat. Quadruped animals have their center of mass in front of their hind legs, whereas, for humans, it is above their legs. So, the bones and muscles are different in structure and have different energy demands. While other animals dissipate their metabolic heat by panting through mouth or nose, humans sweat all over their body. So, as the sweat evaporates, the body cools down to a much greater extent that it would for other animals. (1, 2)
2 In the womb, a fetus grows 250,000 new neurons per minute. That is a million neurons every four minutes for nine straight months.
The human brain starts developing from the tip of a neural tube that’s just three millimeters long. Within three to four weeks after conception, the brain’s three regions — hindbrain, midbrain, and forebrain — start forming. In three months time, the brain would have grown several times in size, especially the forebrain which grows quite fast dominating the other regions. In 15 to 20 weeks time, around the midpoint of the pregnancy, the number of brain cells starts to increase rapidly, and by six months the cerebral cortex begins to separate into two lobes. By the end of nine months, the brain is recognizably human and continues to grow until the baby reaches 18 months of age. Throughout this time, the brain grows at an average rate of 250,000 nerve cells per minute. By the time a baby is born, the brain has more than 100 billion neurons which soon form 100 trillion interconnections.(source)
3 In many instances, if a blood vessel is blocked, like in a stroke, the human body tries to compensate for it by branching new vessels around the part that is circulating poorly.
Human body’s blood circulation system has many redundant branches that become useful when the vessel nearby is blocked. These redundant branches could be preexisting or newly formed. An example of preexisting vascular redundancy is the circle of Willis present in the brain. It has a circular structure and if one part of the circle is blocked or narrowed, or if one of the arteries supplying blood to it is blocked or narrowed, the blood will still flow to the brain preventing stroke.
Forming of new branches around a troubled blood vessel is called “neovascularization.” Functional micro, blood vessel networks large enough for red blood cells to pass through form in response to poor circulation or ischemia and serve as collateral circulation. It has been observed in both animals and humans that after a heart attack new vessels form to bypass the main artery blockage and supply enough oxygen for cardiac tissue repair. It also happens in the eyes, though the bulk of these new branches often causes glaucoma by blocking aqueous humor drainage. (1, 2)
4 When people are electrocuted and thrown far distances, it is a result of sudden and violent muscle contraction and not the result of the shock.
When there is danger, the brain triggers the hypothalamus which is responsible for maintaining the balance between stress and relaxation. It then signals the adrenal glands which in turn releases adrenaline and noradrenaline hormones, starting the fight-or-flight response in our body. This raises the heart rate, increases respiration, dilates the pupils, slows digestion, and most importantly helps the muscles contract. Together, all these factors make our body agile. When confronted with extreme stress, the muscles contract far more than they would in a neutral state or that is voluntarily possible. It can be observed when a person is electrocuted and gets thrown a considerable distance from the source of shock. This is not because of the electric shock itself but because of the involuntary contraction of muscles when the electric charge flows through the body. Scientists believe this demonstrates the potential capabilities of muscle contraction that aren’t used in normal situations. (1, 2)
5 Despite being only 4% of an adult human’s total body mass, the bone marrow produces 500 billion blood cells per day.
The bone marrow is a spongy tissue inside the bones responsible for producing red blood cells, platelets, and white blood cells. It is also an important part of the lymphatic system and supports our body’s immune system. In an adult, bone marrow is present in the spine, hip bones, shoulder bones, ribs, breastbone, and skull. An average adult weighing 65 kilograms has 2.6 kilograms of bone marrow which produces 500 billion blood cells per day.
When the blood cells are mature, they pass through the bone marrow’s circulatory system to enter the blood vessels and start functioning. The bone marrow also contains mesenchymal stem cells which are multipotent stem cells that are capable of becoming a wide variety of cells including cells that form bones, muscle cells, marrow adipose tissue cells, and pancreatic cells. Scientists have recently transformed these stem cells into functional neural cells successfully. (source)
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