|The heart is a pump.
In the human heart diagram, there are four chambers in this tireless pumping organ. All the chambers work in coordination pump blood round the body.The left chambers contain the oxygenated blood from the lungs.
This blood is pumped out of the heart via the arteries which transport the this oxygenated blood round the body to the muscles and vital organs.
The blood returns to the heart via veins. The veins return to the right side of the heart carrying carbon dioxide. The heart pumps this returning blood to the lungs.
In the lungs the carbon dioxide is removed from the blood and breathed out. The carbon dioxide is replaced with oxygen and returned to the left side of the heart to be pumped around the body again.