A Network of Capillaries

The cardiovascular system allows the nutrients essential to life to reach all the cells in our body (it is estimated there are more than 37 thousand billion cells!). The fundamental engine of the system is our heart, an organ of extraordinary complexity and efficiency. The heart pumps the blood into the aorta and from there, through successive ramifications, in the bigger and smaller arteries, then in the arterioles and finally in the capillaries. And it is exactly inside the capillary beds that the nutrients are delivered to the cells and the toxic substances – the residues of the cellular reactions – are removed. The waste CO2, for instance, is transported back through the venous system and is eventually released into the pulmonary alveoli where the respiration expels it.