A human’s heart size is about a size of a person’s fist. It beats about 72 times in a minute but during exercise to 150 times in a minute, Because the muscles need extra oxygen. The heart is made up of four chambers the left atrium, the right atrium, the left ventricle and the right ventricle. There are four valves in the heart which ensures that blood goes only one way, either in or out. Arteries carry blood from the heart or veins carry blood towards the heart. The main artery leaving the left ventricle is the aorta while the main artery leaving the right ventricle is the pulmonary artery. Blood coming from the lungs to the left atrium is carried through the pulmonary veins while blood coming from the body to the right atrium is carried through the superior vena cava inferior vena cava. Vena in Latin means vein and cava means hollow. When the heart contracts, it makes the chambers and pushes blood into the blood vessels. After the heart relaxes again, the chambers get bigger and are then filled with blood coming back in the heart. An adult women’s heart is about 8 ounces and an adult mans heart is 10 ounces. To feel your pulse, place two fingers at pulse points on your neck or wrists. The pulse is blood stopping and starting as it moves through your arteries. As a kid, your resting pulse might be from 90 to 120 beats per minute. As an adult, your pulse rate slows to an average of 72 beats per minute.