The human circulatory system

The body's flow system


The circulatory system is the body’s flow system. All body tissue is nourished via the circulatory system, a complex network of blood vessels. It is more than 100,000 kilometres long and consists of arteries and veins and the finest capillaries connecting arteries and veins with each other. The circulatory system ensures the survival of the organism by supplying the metabolism of each somatic cell.


How blood moves

The arteries carry the oxygen and nutrient rich blood from the heart to all the organs and to the most remote cells and supply tissue with the most important nutrients and oxygen. The pumping function of the heart supports the arteries in this task. Veins, on the other hand, collect the used and oxygen-deficient blood and carry it back to the heart. From there the blood enters the lungs, is again enriched with oxygen and the whole process is repeated.


Tasks and functions

Blood fulfils different tasks in the body. It transports oxygen from the lungs to tissue and carbon dioxide back again. Additionally, tissue is supplied with nutrients from the digestive tract and freed from resulting waste products and metabolic waste that are transported to the excretion organs (kidneys and intestine). Blood also serves as an important vehicle for the transport of hormones between separate organ systems and components of the immune system and blood coagulation in places where they are needed. Moreover, the circulatory system plays an important role in thermoregulation: the degree of the skin’s blood supply regulates heat loss on the body’s surface.