The human heart works by expanding and contracting, or beating, 100,000 times to pump about 2,000 gallons of blood each day, as reported by MedicineNet. It sustains life by pushing nutrient-rich blood and oxygen to all the parts of the body to nourish the cells.
The fist-sized organ is among the most vital parts of the human body, as stated by NetDoctor. It is connected to a system of vesicles that form the circulatory system. Blood is transported from the heart to the rest of the body through the circulatory system. While arteries carry oxygenated blood from the lungs to the heart and to the different part of the body, the veins carry deoxygenated blood from all over the human body.
The lower parts of the heart, which are the ventricles, have thicker muscle linings than the upper parts, which are the atria, explains NetDoctor. During systole, the heart muscles contract in two steps, pushing blood out. In the first step, the upper chambers of the heart contract, forcing blood to flow into the ventricles. The second step involves the contraction of the ventricle muscles to push blood either to the lungs through the vena cava or to the entire body through the aorta. During a diastole, the heart relaxes, allowing blood to fill the upper chambers, and the whole process repeats itself.