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The Cardiovascular System



This week in our organ system section we are going to take a look at the cardiovascular system.

The cardiovascular system is composed of the heart, blood vessels, and blood. Although the lungs are closely related to the heart they have their own system – the respiratory system.


The vasculature is divided into veins and arteries. The veins carry blood toward the heart and the arteries carry blood from the heart to the tissues. The blood transports gases, nutrients, and hormones.


The main function of the cardiovascular system is to deliver oxygen to the tissues whilst at the same time removing the waste product carbon dioxide which is produced by metabolism. Oxygen is bound to the haemoglobin which is present on the red blood cells. To understand more about the makeup of blood, check out the histology spotlight post!


The vascular system can also be classified into circuits. The pulmonary circuit carries blood between the heart and the lungs, and the systemic circuit carries blood between the heart and the peripheries. The heart is a muscular pump and has four chambers, a left, and right atrium and a left and right ventricle. The myocardium, the muscular component of the heart acts under involuntary control. The pulmonary circuit begins in the right ventricle of the heart by carrying deoxygenated blood into the lungs for gas exchange and then brings back oxygenated blood from the lungs into the left atrium of the heart. The systemic circuit kicks in with the left ventricle of the heart pumping oxygenated blood all around the body. Deoxygenated blood is then drained by the systemic veins of the circuit back into the right atrium. Anatomically, it is very easy to tell which side of the heart is right and which is left. The left ventricle is much thicker due to it pumping blood all around the body. The right ventricle is considerably smaller and thinner, and it only deals with the lungs.


The heart is continuously going through a series of contractions and relaxations. Systole is when the ventricles of the heart simultaneously contract. Diastole is when the ventricles relax. When monitored, these numbers tell us the blood pressure and give an indication of the health of the heart.


The heart is an extremely important organ. Next week we will be taking a greater look at the vessels that are a part of the cardiovascular system.

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