Explain why the heart is classed as an organ.
Complete the sentences: The [BLANK] system is made up of the heart and blood vessels. Deoxygenated blood from the body reaches the heart through the [BLANK]. When the heart beats, the ventricles contract. The right ventricle sends deoxygenated blood to the lungs. Its muscular wall is [BLANK] than that of the left ventricle. Gas exchange in the lungs takes place by [BLANK]. Oxygenated blood returns to the heart and enters the [BLANK] of the heart. The left and right sides of the heart are divided by the [BLANK]. This prevents oxygenated and deoxygenated blood from mixing. Oxygenated blood is then carried to the rest of the body. The heart muscle receives its blood supply through the [BLANK].
Many people keep track of their heart rate by counting their pulse. State one other way of monitoring heart rate.