Oxygen in human blood is transported mainly by erythrocytes. In combination with hemoglobin, it forms oxygenated (not oxidized, there is no oxidation reaction between iron and oxygen) hemoglobin (oxyhemoglobin). In contrast, about 3 percent of oxygen is transported in dissolved form in plasma. ¹⁾

The Rh system of human blood was discovered by Karl Landsteiner and Alexander S. Wiener. They were experimenting with the blood of rhesus monkeys at the time. The abbreviation “Rh” comes from “Rhesus.” Because of their ease of breeding and anatomical similarity to humans, these monkeys have been and continue to be frequent laboratory animals. ²⁾

Octopuses and squids have blue blood. Instead of red hemoglobin, copper-containing hemocyanin acts as an oxygen transporter (hence the blue color). At low temperatures and low oxygen concentrations in the water, hemocyanin-based transport is more efficient than hemoglobin-based transport. ³⁾

Which blood type is known as a “universal donor”? Group 0 blood can be transfused to anyone if necessary, as there are no anti-A or anti-B antibodies in it. ⁴⁾

AB is the rarest of the AB0 system groups, and Rh- is always less numerous than Rh+. In western Europe, only 1 percent of the population has AB- blood. In the far east, Rh- is very rare, so in Japan, only 0.05 percent of people have AB- blood. ⁵⁾

Blood is the most important component of any living organism and accounts for about 7% of body weight. ⁶⁾

A newborn baby has about 1 cup of blood in its body. ⁷⁾

About 55% of our blood consists of plasma. ⁸⁾

Plasma is a carrier base for morphotic elements. It contains organic and inorganic components. Inorganic components are sodium, potassium, chloride, and carbonate ions. Organic components are proteins, non-protein nitrogenous and nitrogen-free components, and plasma lipids. ⁹⁾

Leukocytes are found in blood, lymph, and connective tissue. They are formed in the bone marrow and the lymphoid system (thymus, spleen, lymph nodes, and lymph nodes). In the blood of a healthy person, there are 4-10 thousand /mm3. They are divided into granulocytes, lymphocytes, and monocytes. ¹⁰⁾

The immature form of the red blood cell is the reticulocyte. The number of reticulocytes in the blood illustrates the rate of production by the bone marrow. ¹¹⁾

Lymphocytes remember their enemies. They are able to recognize them and fend off an attack even decades after they first suffered a disease. ¹²⁾

Granulocytes are divided into neutrophils, eosinophils, and basophils. Neutrophils (neutrophilic granulocytes) make up about 60% of leukocytes. They defend the body against infections and phagocytose pathogenic microorganisms. Eosinophils (acidophilic granulocytes) make up 2-5% of leukocytes. Their number increases after parasite infection and with allergies. Basophils (basophilic granulocytes) produce heparin, a substance that prevents blood clotting. ¹³⁾

Thrombocytes (platelets) are responsible for blood clotting. They are fragments of the cytoplasm of marrow cells or megakaryocytes. They live for up to 10 days, after which they are broken down in the spleen. In human blood, they are present in the amount of 200-300 thousand/mm3. ¹⁴⁾

In the blood is stored most of the organism's information. Just 0.05 ml of blood contains the complete genome or 3 billion pairs of nucleotides. ¹⁵⁾

People with blood type O are less likely to suffer heart attacks and strokes than those with blood type AB. ¹⁶⁾

Swedish scientists have succeeded in obtaining synthetic blood from stem cells. ¹⁷⁾

Probably 20000 years ago, all humans had the same blood type - 0. It was only when man shifted from nomadic to a sedentary mode that a new blood type - A. The AB type was created about 1000 years ago. ¹⁸⁾