The Human Heart Acts A Pump

The human heart acts a pump and it contains four chambers: two atria, which receive venous blood, and two ventricles, which pump blood into the arterial system. Arteries carry blood away from the heart and veins carry blood to the heart. Atria are the upper chambers and ventricles are the lower chambers of the heart. The flow of blood is as follows. Blood, with low oxygen and high carbon dioxide content, returns to the right atrium of the heart from the body via the inferior and superior vena cava, which are the largest veins in the body. The blood flows through the right atrioventricular (AV) (or tricuspid) valve to the right ventricle. Then the blood goes through the pulmonary semilunar valve, through the pulmonary arteries and to the lungs, in order to oxygenate and deplete carbon dioxide in the blood. The blood returns to the heart via pulmonary veins and into the left atrium. This path of blood from the right ventricle of the heart, through the lungs and back to left atrium of the heart is called pulmonary circulation. Then, the blood goes through the left atrioventricular (also called bicuspid or mitral) valve and into the left ventricle. The blood is then pumped through the aortic semilunar valve and into the aorta, which is the largest artery in the human body, and supplies the body with oxygen-rich blood. The arterial branches from the aorta that supply the body with this blood are part of the systemic circulation. The systemic arterial blood pressure rises and falls during each heartbeat due to the rhythmic flow of blood.

A cardiac cycle is a period of time that extends from the end of one heartbeat to the end of the next. During each cycle, pressure changes occur within the chambers of the heart as they relax and contra...

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... pressure’ where a normal blood pressure is 120/80 mmHg. The sphygmomanometer consists of an inflating bulb which creates extra-arterial pressure in a cuff that is wrapped around a subject’s arm. The manometer on the sphygmomanometer measures the applied pressure. Arterial sounds, which are called Korotkoff sounds, can be heard through a stethoscope to determine the systemic arterial blood pressure. The first loud whooshing noise heard, when the cuff pressure is about 140-160 mmHg, is equal to the systolic blood pressure. The sound is a product of a partially occlude artery during ventricular systole. As air is released from the cuff, the arterial flow becomes less turbulent and the sounds fade away. When the sounds disappear, this is the diastolic pressure reading; since the artery is no longer occluded, blood flows freely and thus produces no sound (Johnson 2013).