The Heart as a Pump in the Cardiovascular System
The cardiovascular system is one which is responsible for the circulation of blood throughout the whole body. This is achieved by a ‘pump’, the heart, giving energy for the blood to flow and a vascular system conducting the blood from the heart to the different organs of the body.
Chambers of the Heart
The heart in the human, like in all other mammals, is divided into two compartments. De-oxygenated blood (i.e. the blood which has a lesser concentration of oxygen because of being consumed by the body) flows through the right compartment, while oxygenated blood (i.e. the blood of which the oxygen concentration is increased by flowing through the lungs) flows through the left. Each of these compartments is again divided in to an atrium and a ventricle. Thus, the human heart has four chambers, namely: the right atrium, the right ventricle, the left atrium and the left ventricle.
Muscles of the Heart - the Cardiac Muscle
The heart is made-up of a special type of muscle cells known as the cardiac muscle. This type of muscle, being unique to the heart, has its ability to function taking only a rest for a fraction of a second, without getting tired. The cardiac muscle is organized around the chambers in the heart so that their contraction could increase the pressure within the particular chamber, drawing the contents of the chamber out of the heart.
How does the heart pump?
The atria receive blood from the incoming vessels, known as the great veins, and stores blood for a short period of time. The inferior vena cava and the superior vena cava, channel down the blood which had been distributed throughout the whole body, and therefore is deoxygenated, to the right atrium. With the contraction of the right atrium, the blood flows through the one-way tricuspid valve, to the right ventricle. With the contraction of the right ventricle, the blood is then pumped out through the pulmonary artery to the lungs. The pulmonary artery also has a valve preventing the back flow of the blood during the relaxation of the right ventricle. The blood ejected through the pulmonary artery reaches the lung and is oxygenated in the lungs, when the blood comes in close contact with the air in the lungs. This oxygenated blood then flows through the pulmonary veins to the left atrium. With the contraction of the left atrium, while the left ventricle is relaxing, the oxygenated blood flows to the left ventricle through another one-way valve known as the mitral valve. With the contraction of the left ventricle, the blood is then distributed throughout the body, by flowing through the aorta and its branches. The aorta also has a semi-lunar valve preventing the back flow of blood into the left ventricle.
This article is just a simplified summary of how the heart is organized and how it functions. The details of cardiovascular physiology will be discussed later in this series of articles for those who are interested. The next article in this series will be on the vascular system of the body and their structure.