The heart is the “engine,” and the blood is the “fuel.” Around five to six liters of blood flows through the human body and accounts for about eight percent of body weight. Through blood vessels, the blood supplies the entire body with vital substances, without which the functionality of the organism can no longer be guaranteed.
What is blood?
Erythrocytes or red blood cells are the most abundant cells in human blood. Among other things, they serve to transport oxygen from the lungs to the organs, bones, and tissues. Erythrocytes make the blood appear red. Click to enlarge. Proverbially, the blood in our veins can falter, freeze or be hot for appropriate temper. So blood circulation air-conditions the body. It is also true that blood reacts to changes in the organism and wards off diseases like no other organ. On its way the blood circulation leads from the roots of the hair to the tips of the toes through the entire body, the blood transports nutrients, oxygen and toxins. Defined blood is a body fluid that ensures the functions of the body with the support of the cardiovascular system. Blood is made up of the protein and water containing plasma, which acts as a cell carrier. These are the red blood cells, the erythrocytes, which also give the blood its dark red color, the white blood cells, the leukocytes, and the platelets, the thrombocytes. The heart pumps blood through all the blood vessels, which in each body are almost 100,000 kilometers (!) long in total. In this enormous task, the heart can be supported and relieved by the work of trained muscles and the venous valves. In the narrower sense, therefore, the blood is a body fluid, although it is referred to as a “liquid organ” or also as “liquid tissue” because of its many functions. As a central element of metabolism, the body cannot do without the smooth cycle of blood. For every kilogram of body weight, there are an estimated 70 milliliters of blood, which in an adult human gives a total of about five to six liters of blood transported through the vascular system. Since the amount of blood present in the body correlates with the respective body weight, the rule of thumb is that women have on average one liter less blood than men. This fact is due to the higher body weight of men compared to women.
Anatomy and structure
Blood is not a homogeneous mass, but is made up of a variety of different components. At about 50 percent, plasma represents the largest component of blood. In second place, at 42 percent, are the red blood cells, also known as erythrocytes. Another four percent of the blood is made up of proteins, while platelets (also known as thrombocytes) make up only two percent of the blood. One percent is also made up of all the fat, sugar and salt found in the blood. Finally, the white blood cells, also known as leukocytes in medical jargon, account for considerably less than one percent, or to be more precise, only 0.07 percent. Thus, only half of the blood consists of solid components, while the other half is the liquid blood plasma: a 90 percent aqueous solution whose main task is the smooth “movement” of the blood within the vascular system. Vessels that lead away from the heart are called arteries. They have a strong, muscular structure to withstand the high pressure from the heart. The arteries branch out more and more and become arioles and capillaries. Here, the vessel walls are thin and permeable in order to be able to transfer nutrients and oxygen to the individual cells and to discharge waste products. Once the waste products have been passed on to the degrading organs, the blood vessels dilate again. On their way back to the heart, they are called veins. In simple terms, this is the circulation of blood. Before the blood enters this pathway again, it is pumped from the heart to the lungs via the small pulmonary circulation to refuel with oxygen. Enriched with oxygen, the cycle begins again.
Functions and tasks
The blood thus flows through the lungs and liver, the mouth, muscles and brain, as well as all other body cells and organs.Each individual component of the blood fulfills its own special tasks on its long journey through the organism:
Probably the most important task of the blood is to distribute oxygen, which is inhaled through the lungs, and sugar, which is absorbed into the organism in the gastrointestinal tract, throughout the body via the extensive vascular system, i.e. to supply each individual cell. On the other hand, it is again the responsibility of the blood to transport away the metabolic products that have been produced and that the cells no longer need, such as carbon dioxide and urea. However, the individual cells in the body are not only dependent on the permanent supply of certain substances. For example, commands ordered by the brain must be passed on to the cells in the form of messenger substances. This transmission also takes place via the blood, which gives it the function of a command network. On its way through the lungs, the red blood cells have the task of absorbing the atmospheric oxygen breathed into the lungs. In this way, all the cells of the body are continuously supplied with oxygen. The oxygen is the generator of the cells, which thereby gain their “life energy”. The by-product of the continuous breakdown of oxygen is carbon dioxide. This, too, is transported by the blood; back in the lungs, it is exhaled again. Replenishment of valuable erythrocytes is produced in the red bone marrow. They function (work) for a period of about four months. They are finally broken down again in the spleen. On its way through the intestine, the blood absorbs the nutrients that have been broken down and crushed there by the digestive processes. Again, the plasma transports these food building blocks to the individual cells, which utilize them further. Here, toxic breakdown products accumulate and travel to the kidneys and liver to be rendered harmless. Exertion and excitement increase the blood flow through the veins. The skin then gives off more heat. Conversely, we pale in winter, for example, because less blood is sent to the surface of the skin so that no heat is lost unnecessarily. This climate-regulating blood function is complemented by the function of the white blood cells as the body’s own immune defense system. The leukocytes protect the organism against infections. Although they are present in smaller numbers, they are twice the size of erythrocytes in the blood. White blood cells can move independently. Thus, they have the ability to either render pathogens harmless by antibodies or simply “eat them up”. They are also produced in the bone marrow. The colorless, thin platelets also come from there. Their task is to quickly clog wounds. They thus regulate blood clotting. As already mentioned, about five to six liters of blood flow in the body of adult humans. In the event of infection with a disease that spreads via the bloodstream, it would have fatal consequences in terms of the rapid spread of the invading pathogen if the blood did not have defense mechanisms, given the extensive vascular system of humans. Its nonspecific or innate defenses, as well as its specific defenses provided by the phagocytes and antibodies found in the blood, ensure that the body can respond quickly to the invaders and destroy them while they are still in the bloodstream.
Diseases
If the impressive system of blood and its two circuits comes to harm because individual components have become diseased, the blood loses parts of its capabilities. The blood disease hemophilia destroys the blood clotting function with devastating consequences of any injury. If red blood cells are missing, we speak of anemia, which impairs oxygen transport. Because of its interconnectedness, diseases of the blood can have particularly severe consequences. Even the smallest failure to supply the body with proper blood can lead to serious secondary diseases, such as cerebral infarction. The most common blood diseases include acute and chronic leukemia: blood cancer. Characteristic of leukemia is that the composition of the blood changes in an unnatural way. While the number of red blood cells, whose task is to transport oxygen and sugar and to remove carbon dioxide, decreases, the proportion of white blood cells in their early and thus still non-functional precursors increases. Anemia (anemia) is also relatively common.As the name suggests, those affected suffer from a general lack of blood, i.e., less than the average five to six liters of blood flow in their blood vessels. Finally, the typical blood disorders include hemophilia: even the smallest skin lesions cause affected individuals to lose large quantities of blood. Here, too, the reason lies in the incorrect composition of the blood. Injuries are first “cemented” by the platelets found in the blood before other components of the blood plasma ensure that the blood coagulates, thus preventing blood loss through the injury. Many patients can be helped with medication. Sometimes, however, blood transfusions have to be administered, for example to compensate for high blood losses. To ensure that the body’s own white blood cells do not fight the supplied blood as an avoidable danger, it is necessary to match the blood groups of the donor and the recipient.
Typical and common diseases
- Acute lymphoblastic leukemia
- Acute myeloid leukemia
- Chronic lymphocytic leukemia
- Chronic myeloid leukemia
- Blood poisoning
