Know your heart
Your heart is a hollow muscle about the size of your closed fist. Every time your heart “beats”, it pumps blood containing oxygen and nutrients to all parts of your body. Blood is carried to your tissues and organs through a network of blood vessels called arteries. A single red blood cell makes approximately 250,000 round trips of the body, before returning to the bone marrow, where it was born, to die.
Heart anatomy – simplified
Your heart is made up of four chambers; two chambers on top and two below. The upper chambers are called atria (single chamber is called an atrium). The lower chambers are called ventricles. The muscle walls, called septa (single wall is called a septum), separate the left and the right atrium, and the left and right ventricles respectively. Blood flows from the atrium to the ventricle through valves. Valves work like one-way doors, letting blood flow through them in only one direction.
The impure blood from the rest of the body is brought to the right atrium. This passes into the right ventricle. The right ventricle contracts, and blood is forced into the pulmonary artery. The blood travels through the lungs, thereby purifying and oxygenating the lungs, and returning to the heart through the left atrium. Then the blood flows into the left ventricle. The ventricle contracts and the blood goes rushing into the aorta and to the other parts of the body.
The circulatory system: To do both functions (pumping blood to the rest of the body and sending blood to be purified in the lungs) effectively, the heart needs a supply of oxygenated blood, just like any other part of the body. The coronary arteries, which rise from the aorta, supply oxygen-rich blood to the heart muscle.