Blood is a fluid tissue whose complexity and multi-faceted nature make it more than just the red fluid that circulates in our veins. Each drop of blood, although inconspicuous, is full of life and dynamic processes that allow the body to function almost flawlessly. The human body produces about 2 million red blood cells per second, which gives an amazing picture of how quickly and precisely our body renews the key component of blood – erythrocytes.. Red blood cells constantly move through the network of blood vessels, providing oxygen to every cell in the body and enabling them to breathe and produce energy.
But blood it is not only a life-giving oxygen carrier. It is also an example of the so-called non-Newtonian fluid. This means that its viscosity changes depending on the forces acting on it. This phenomenon may seem abstract, but it is extremely important for the health and functioning of the body. Under normal conditions, blood flows freely, but when the body is injured or the pressure on the vessels increases – the viscosity of the blood changes, allowing it to clot more effectively at the sites of injury. This elastic behavior of non-Newtonian fluid is one of many “masterpieces” that evolution has developed to ensure our survival.
The amount of blood in a person’s body depends on his or her age, gender and body weight. In an adultblood constitutes about 7-8% of body weight. With a weight of about 70 kg, an adult has on average 4.5 to 6 liters of blood. This amount may change depending on the level of hydration, health and condition of the body. Women typically have slightly less blood than men due to differences in hormones and body weight. In women, the amount of blood ranges from 4 to 5 liters, while in men it is usually from 5 to 6 liters.
Children have a correspondingly smaller blood volume, which is approximately 70-80 ml per kilogram in proportion to their body weight. Newborn weighing 3,5 kg will have approximately 250-280 ml of blood. However, as in adults, this proportion is closely related to body weight, so larger children have a larger blood volume.
It is also worth mentioning athletes whose circulatory system is often more efficient, therefore, the volume of blood in their bodies tends to be slightly greater. The body adapts to the higher demand for oxygen during exercise, which results in increased red blood cell production and overall blood volume.
Blood consists mainly of plasma – a clear, yellowish liquid that is 90% water. This “liquid river” carries countless amounts of protein, glucose, hormones, electrolytes and metabolic products. There are three main types of cells suspended in plasma: erythrocytes, leukocytes i trombocyty. Each of these cells performs separate tasks:
- erythrocytes – in addition to transporting oxygen, they contain hemoglobin – a protein that gives blood its characteristic red color. These cells have their limits, they live for about 120 days, after which they are replaced by new ones, in a constant cycle of renewal;
- leukocytes – white blood cells are the “soldiers” of our immunity, protecting us against external threats such as viruses, bacteria and other pathogens. They act as a specialized army that recognizes, attacks and neutralizes intruders before they can do more damage. There are several types of leukocytes – from fast “attacking” neutrophils to strategic lymphocytes that are responsible for long-term immunological memory;
- trombocyty – also known as platelets, are our “rescuers” at the time of injury. When a blood vessel is damaged, platelets quickly accumulate at the site of the injury and initiate the process of clot formation, closing the damage and preventing excessive blood loss. Together with plasma proteins such as fibrinogen, platelets play a role in the complex clotting mechanism that protects us from bleeding.
However, the functions of blood are not limited to transport and protection. Blood participates in maintaining homeostasis, i.e. the body’s internal balance. It is responsible for regulating body temperature, distributing heat throughout the body, and maintaining the proper pH level and water and electrolyte balance. When the body is faced with stress or infection, the blood responds immediately, mobilizing resources and delivering the right substances where they are needed most.
Blood performs a number of key functions in the body, without which life would be impossible. It is a complex delivery system that not only transports substances needed for the proper functioning of the body, but also protects the body against threats and regulates its internal environment. Its most important functions include:
- transport of substances: delivers oxygen to the tissues, removes dioxide from the tissues so that the body can expel it during exhalation. It also carries nutrients (glucose, amino acids) to cells and transports hormones. It also removes waste products such as urea, which are eliminated by the kidneys;
- regulation of homeostasis: regulates body temperature by distributing heat or limiting heat loss. Maintains constant pH and appropriate water and electrolyte balance so that muscles and nerves can function properly;
- immune protection: leukocytes fight viral and bacterial infections and other pathogens. Blood also contains antibodies that neutralize harmful microorganisms, supporting the body in fighting diseases;
- transport of immune cells and medicinal substances: transports stem cells and substances supporting tissue regeneration and healing. At the same time, they provide ingredients necessary to repair damage and support the fight against infections;
- removal of toxins and metabolic waste: the blood transports waste products such as ammonia and uric acid to the kidneys and liver, where they are removed. This process helps the body get rid of harmful substances.
In 2024, blood research has brought new, fascinating discoveries. A team of researchers from Harvard Medical School discovered that blood contains not only already known elements, but also microscopic RNA molecules that can play a key role in regulating genetic processes. This newly discovered blood function may open new paths in the diagnosis and treatment of many diseases, including cancer.
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