Also called a pulse, a heartbeat is heard through the arteries in different parts of the body. The heart pumps blood into the arteries, and when an artery is pressed against the skin, the pulse is heard. The closer the artery to the skin, the stronger the pulse is.
A person's pulse is often felt through the arteries on the wrist on the side of the thumb, right under the side of the jaw, on the opposite side of the elbow and behind the knee among others. Long before the stethoscope was invented, early physicians uses the pulse to determine a person's heartbeat. This method is still used until today.