The circulatory system is made up by an extended network of conduits that blood flows through.
Blood has two main missions: to ensure that oxygen and nutrients reach every cell in the body and discard waste products. Blood travels through this closed circuit at high speed, propelled by the force of the heart. It is an endless back-and-forth journey through transportation tubes, which, if lined up, would measure no less than 150,000 kilometers.
These blood conduits come in three types: arteries, veins and capillaries.
The heart pumps oxygen-rich blood through the arteries. Their sturdiness and elasticity allow them to endure the strong pressure exerted by the bloodstream.
From the arteries, blood passes to the arterioles, and then to the capillary vessels, which is a network of finer structures that irrigate the tissues and where nutrients and oxygen are transported to the cells.
This is the first part of the circuit. The second part also starts here; cell waste enters the capillaries and then moves on to the venules and veins, which are in charge of carrying blood back to the heart.
The circulatory system is divided in two routes connected to the heart:
– Pulmonary or lesser circulation: it ensures the oxygenation of blood and goes from the heart to the lungs.
– Systemic or greater circulation: it begins and ends in the heart and spans all the organs of the body.
Purifying circuits
A considerable portion of the purifying process of blood is carried out by the lungs through lesser circulation. Nevertheless, there are two circuits that also cleanse blood of toxic substances: the liver and the kidneys collaborate in this filtration process.
Blood passes on to the liver through the hepatic portal vein, where nutrients are stored and toxins are also eliminated. Blood enters the kidneys through the renal artery. There, the excess pollutants of the bloodstream are disposed of.
