The circulatory system reaches into almost every corner of the body to supply cells with oxygen and nutrients. Find out here why bottlenecks sometimes occur and what helps blood circulation get going.
For humans, the circulatory system is both a supply and disposal system: it transports oxygen and nutrients to the tissues and organs and removes waste products from the metabolism. At the same time, it is involved in regulating the acid-base balance and body temperature, and it brings immune cells to where they are needed to fight pathogens.
The circulatory system can probably best be compared to a complex system of tubes that branches out further and further and finally reunites to form a closed circuit. This vascular system is more than 100,000 kilometers long in an adult human and would thus extend more than twice around the equator.
The heart
As the driving engine, the heart ensures that the bloodstream always keeps moving. With more than 100,000 beats a day, the fist-sized muscle pumps oxygen– and nutrient-rich blood through the arteries from its left ventricle. This is done at high pressure so that it reaches every nook and cranny in the body. In the organs, the blood vessels branch out into a network of very thin vessels called capillaries. It is mainly in this part of the circulatory system that oxygen and nutrients pass from the blood to the tissues, and at the same time waste products from cell metabolism are absorbed.
The blood is not evenly distributed in the body, but is always adjusted to the current demand in the individual organs. Thus, during sports or heavy physical work, the capillary blood flow in the affected muscles can increase 20 to 50 times. From the capillaries, the oxygen- and nutrient-poor blood finally flows back into the veins and from here into the right ventricle. Because the flow velocity in the veins has already decreased considerably, small valves ensure that the blood flow is always in the direction of the heart and that the blood does not become congested.
From the right ventricle, the blood then reaches the lungs. Here, the red blood cells release the carbon dioxide from cell metabolism and take up oxygen. It then reaches the left ventricle again and is again pumped through the arteries to the organs. In the course of a day, the red lifeblood travels about 270,000 kilometers on this path.
