Many popular science sources say that the total length of blood vessels in the human body is two and a half times larger than the length of the equator. We checked whether this statement is correct.

Users write about the incredible total length of blood vessels services questions and answers, Reddit And Instagram*dedicated to donation Publics on VKontakte, Private clinics And Russian Regional Media. The statement is found in training presentations On the sites of medical colleges and universities, on Portal "Education in Russia" and in Recommendations for the preparation of biology lessons for the 8th grade.

The vessels are tubular structuresby which blood and lymph circulate throughout the human body. Although vessels are often called exclusively components of the circulatory system, there are also lymph vessels. But, since in most viral publications we are talking about the total length of the blood vessels, then in the text this term will be used in this meaning.

Blood vessels form a system of channels closed on the heart. First of all, they provide the delivery of oxygen and nutrients to organs and tissues, as well as the excretion of metabolism. Basic Types of blood vessels: arteries (tolerate blood from the heart), veins (tolerate blood to the heart) and capillaries (connect arteries and veins). Due to the possibility of narrowing and expanding the vessels also participate in thermoregulation. More In total, the vessels are located in tissues and organs with high metabolic activity and the need for oxygen (for example, in muscles, lungs, liver, kidneys and brain), the least in avascular structures where the metabolism is poorly intended (these include cartilage, eye corneal, lens, and some tendons).

The beginning of the study of blood vessels Put The Roman doctor Galen, who lived in the II - III centuries. True, he believed that blood is formed in the liver and does not circulate, but slowly, with progressive movements, moves through the veins in the lower body (the arteries do not play any role). With some reservations, this point of view prevailed until the 16th century, when the Flemish physician and founder of modern anatomy Andreas Vesaliy held the first systematic autopsy of human bodies and refuted many statements of Galen. And in 1628, the English doctor William Harvey published the work of Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus (“Anatomical examination of the movement of the heart and blood in animals”), where he experimentally and logically proved: the blood moves through a closed circle due to the work of the heart. Its discoveries laid the basis of modern cardiology and vascular physiology.

A significant contribution to the study of blood vessels was made by the Danish physiologist August Krog - he studies his research in this area in 1920 received Nobel Prize for Medicine and Physiology. It is Krog and I calculated The length of all blood vessels of the human body is approximately 100,000 km. True, the average person of those calculations was absolutely different from the average person in reality - his weight was 143 kg, of which 50 kg were muscles (for comparison, about so much at the peak of his sports career Weighed Boxer Nikolai Valuev). According to 2005, the average weight of a person composed 62 kg, that is, more than half as much as the reference person of the crog. At the same time, the ratio of its muscle mass and body weight looks quite realistic: so, depending on age, in men on the muscles It is necessary From 31% to 44% of total weight, and in women - from 26% to 33%. In the same range as Show Some studies, this indicator is located among athletes involved in American football, powerlifting, sumo and pushing the nucleus.

In 2022, a group of American and Japanese scientists Counted The length of the vessels in the human body, trying to eliminate the shortcomings of studies of a century ago. For the weight of the average person, they took 70 kg and suggested that the muscles make up 35% of the weight. Scientists also took into account that Krog used an incorrect assessment of vascularization (density of capillaries in the muscles), and took clarified modern data. However, such calculations will have restrictions - vascularization varies depending on the fabric: in the heart it higherthan in skeletal muscles, and back muscles higherthan in the buttocks. As a result, scientists came to the conclusion that the total length of the vessels in the human body (with all averages and assumptions) is from 9,000 to 19,000 km. Although this figure does not exceed the length of the equator by two and a half times, it is still impressive - for comparison, the path along the highway from Kaliningrad to Vladivostok It is 10 337 km.

True, this data should be treated with caution. Firstly, the length of the capillaries is not fixed-they constantly grow and disappear. This process called neoangiogenesis is one of the main mechanisms general exchange To maintain body temperature. Secondly, it is important to remember that the blood system Represents Fractal and has a fractal dimension. Because of this, the correctness of any statement about the total length of all vessels depends, including on the scale chosen by the researcher and the degree of details of the studied object.

Thus, the assessment of the length of all human vessels of 100,000 km is a completely scientific calculation that, back in the 1920s, was held by the Nobel laureate August Krog. However, firstly, in his model, a scientist, instead of an average person, used a real giant, and secondly, modern data showed that he greatly overestimated the density of the capillary in the muscles. According to current calculations, the total length of blood vessels in the human body weighing 70 kg is from 9,000 to 19,000 km.

Image on the cover: Image by Arek Socha from Pixabay

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