How does the Circulatory System Work

The circulatory system consists of the heart, blood vessels and blood. Blood vessels encompasses arteries, arterioles, veins and capillaries. All these parts play a major role in the normal functioning of the circulatory or cardiovascular system. The basic structure of the circulatory system can be considered as a closed loop that starts and finishes at the heart. For better understanding of the circulatory system, let's first discuss about the heart.

Heart: The human heart is divided into four chambers - left atrium, left ventricle, right atrium and right ventricle. The ventricle walls are thicker and stronger as compared to the atria walls. The right atrium is the upper and right chamber that receives deoxygenated blood via the superior vena cava (for upper body) and inferior vena cava (for lower body). The left atrium collects the oxygenated blood from the pulmonary veins and is pumped into the aorta (biggest artery of the heart), to be distributed to arteries and arterioles.

How does the Circulatory System Work

The main function of the circulatory system is to provide nutrients and oxygen to the various parts of the body, via the blood, which is circulated through the veins and arteries. Arteries carry the oxygenated blood from the heart to the cells and tissues, whereas veins return the oxygen-depleted blood from the cells to the heart. The circulatory system can be classified into the following two categories:

The Systemic Circulation: The systemic circulation is a loop from the heart to the various parts of the body, which works in contrast to the pulmonary circulation. In the systemic circulation, arteries collect the oxygen-rich blood from the heart and is transported to the body tissues. In the process, oxygen from the blood is diffused into the body cells; whereas carbon dioxide from the cells is diffused in the blood. This exchange of gases takes place with the help of capillaries that surround the body cells.

The Pulmonary Circulation: In the circulatory system, the pulmonary circulation is a loop from the heart to the lungs. It is that portion, where deoxygenated blood from the heart is carried to the lungs and in turn, returns oxygenated blood to the heart. The oxygen-depleted blood leaves the heart (right ventricle) through the two pulmonary arteries and moves into the lungs. In the lungs, respiration takes place in which the red blood cells (RBCs) release carbon dioxide and absorbs oxygen. Oxygenated blood from the lungs is then carried back to the heart (left atrium) with the help of pulmonary veins. The systemic circulation distributes this oxygen-rich blood to the body parts.

A cardiac cycle is defined as one complete heart beat, which comprises two phases - systole and diastole. In the former case, contraction of ventricles takes place to pump blood for pulmonary and systemic circulation; whereas, the ventricles relax and blood is filled in the atria in diastole phase. Any disorder in the heart and blood vessels can cause heart disease such as heart attacks and hypertension.

The circulatory system works in association with the other systems of the body. For example, the circulatory system works in coordination with the respiratory system and digestive system to supply oxygen and nutrients to the body. Blood carries the messenger chemicals - hormones, secreted by the organs of the endocrine system. Thus, the circulatory system is also responsible for circulating hormones for proper communication between the body organs.