There are more blood types than four and women's hearts beat faster: five startling facts about the human body

Throughout its existence, mankind has been trying to comprehend the secrets of the universe. It is still on the path of discovery and search for clues about the world around us. However, the way our own bodies are organized remains no less mysterious to us.

Most people are not even aware of many properties of their bodies. OBOZ.UA has collected five surprising facts about the human body that you didn't know about.

1. We see the world upside down

In fact, the fact that human eyes see the world upside down was proved by physicist René Descartes in the 17th century. He conducted an experiment: he projected an image of a cut-out bull's eye onto a paper screen. It turned out to be inverted, in accordance with all the laws of physics.

The reason for this phenomenon is that light is refracted when it passes through the cornea and lens, so the projection of a visible object appears inverted.

We perceive what surrounds us in the usual way, not upside down, thanks to our brain: it turns the image backwards, making it correspond to reality, and at the same time "glues" the image from two retinas into one.

This feature of the human brain was proved in the late 19th century by psychologist George Stretton. As an experiment, he wore special glasses that reversed images for eight days. On the fifth day, his brain simply stopped correcting the image, and Stretton began to see the world normally again. However, when he took off the glasses, it took some time for his brain to get used to the fact that the experiment had stopped.

2. Three kilograms of bacteria live in every person

Scientists have found that the number of bacteria living in the human body is three times higher than the number of its own cells. However, compared to how much the body weighs, they are quite small: a person 170 meters tall and weighing 70 kg will have 1 to 3 kg of bacteria in the body.

In addition to bacteria, we also have archaea, fungi, protists, and viruses in our bodies. Some of them help us live as they participate in digestion and protect us from pathogens and harmful substances. Some of them exist without bothering us. And the purpose and role of another part is still a mystery.

3. Only four blood types is a misconception

It is generally accepted that there are only four blood types. The first (0) accounts for approximately 48% of the population, the second (A) for 36%, the third (B) for 11%, and the fourth (AB) for 5%.

However, this is not entirely true: according to the International Society of Blood Transfusion, there are 29 blood types in the world.

The traditional four groups are distinguished by the AB0 and Rhesus antigens. However, there are other factors of difference. Many of them are named after patients who first discovered the corresponding antibodies. Scientists suggest that this is not the limit and that new discoveries are possible.

4. Women's hearts beat faster

A woman's heart beats 78-82 times per minute, while men's heart rate is approximately 70-72 times per minute.

The reason for this difference is that female sex hormones affect myocardial cells, accelerating their contraction. However, such a feature of the heart in women leads to the fact that they are more likely to suffer from tachycardia and arrhythmias.

5. A person produces up to 1.5 liters of saliva per day

Human salivary glands produce from two to six glasses of saliva per day, which is 0.5-1.5 liters. We manage not to drown with this amount of liquid only because we swallow it reflexively.

During sleep, a person has not yet learned to swallow. And here the body itself comes to the rescue. It simply reduces the amount of saliva produced. That is why, when we wake up in the morning, we usually feel dry mouth.

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