The human body is remarkably complex, and a scientist could spend her or his entire life devoted to studying just one organ, part or system. By learning more about the body, scientists discover new methods to treat ailments and repair aging parts as they wear out.

There are always new things to learn about how our bodies are put together and how they work. With that in mind, here are some wonderfully surprising facts about the human body:

Our Bodies Came from the Stars

All living creatures on Earth are made from the same building blocks. For example, we are mostly composed of water, which is made from hydrogen and oxygen. The elements that went into making every living thing on Earth were created during the Big Bang, which heralded the start of the universe.

Hydrogen is the most common element in the universe, made from stars between 7 billion and 12 billion years ago. As the song goes, we are all stardust.

We Are Made of Atoms

The smallest indivisible piece of any substance, such as gold, carbon or hydrogen is the atom. Our bodies are composed of about 7,000,000,000,000,000,000,000,000,000 – or 7 octillion – atoms.

Changing Stomach

The lining of our stomach is constantly being replaced. When we eat, powerful digestive acids break down the food as well as the stomach lining itself. The body generates a new stomach lining every three or four days so we can keep eating.

Biggest Organ

The biggest organ of the human body is one that you can see every day: it’s the skin. Our skin plays an important role, providing a protective covering to hold all of our insides together and keeping out things that don’t belong, such as dirt and disease. Skin also holds in our body heat and allows us to perspire when we need to cool down.

A major feature of our skin is the many nerve endings, which enable us to feel our environment.

Shedding Skin

When you hear the word shedding, you probably think of how your pet dog or cat sheds fur all over the furniture in the house. However, humans shed as well. In fact, besides losing strands of hair, such as when using a brush or taking a shower, we lose about 600,000 skin particles every hour or about one and a half pounds every single year.

By the time a person reaches the age of 70, he will have likely shed about 105 pounds of skin. As older skin particles fall away, our body makes new ones constantly to replenish what we lose.

Collection of Bones

When we are born, each person has 350 bones in total. However, as you grow up, bones start to fuse together and become stronger. The result is every adult winds up with 206 bones.

Organized Intestines

Inside the abdomen, the small intestine ranges from 18 feet to 23 feet. In order to fit this inside our body, the intestine is organized inside the abdominal cavity by looping repeatedly, back and forth.

Strong Heart

Every person’s heart beats approximately 100,000 times every day or 36,500,000 times per year.

A Bunch of Bacteria

Bacteria are too small to be seen with the naked eye, but we can easily detect them with microscopes. Scientists have discovered that normally about 1 trillion bacteria live inside the body and on the surface of the skin.

The bacteria in a person’s intestines may weigh as much as one to two pounds. Not all bacteria are harmful. The ones inside our gut help us out in a variety of ways, including breaking down material that we can’t digest ourselves and producing vitamin K.

Well-Connected Brain

The human brain weighs about three pounds and is the most complicated structure in our body. Its interconnected neurons rival the network of computers we rely on.

Neuroscientists estimate that our brains have as many as 100 billion neurons.

Bones Improve With Exercise

Many people think that exercise is only beneficial to our muscles, since we use our muscles to move around. However, there is another benefit to exercising: it actually can strengthen our bones.

By putting stress on our bodies during exercise, the bones respond by becoming stronger, which is especially useful for people as they age, as it combats osteoporosis.

New Blood

Our body uses blood to carry oxygen and nutrients around the body and to remove waste products. Eventually, our red blood cells wear out and we need to replenish them.

It takes about six weeks to completely regenerate our red blood cells, which is why blood donation facilities typically make donors wait two months in between whole blood donations.

Eyes on the Move

We use our eye focusing muscles approximately 100,000 times every day, which is why you might feel tired after a long day of reading, using computers and driving. The equivalent activity for our legs would require us to walk more than 50 miles daily.

Our eyelids, which protect our eyes from dirt, dust and other flying debris, move as many as 25 times per minute when we blink, which adds up to about 6 million eye blinks per year.

As you can see, people don’t need to be doctors or research scientists to appreciate all the amazing facts about the human body.

What other fascinating human body facts can you add to the list?