Mysteries of the Heart

Today, we began the circulatory system, by far the most confusing. Because the heart has a confusing pathway, I decided to write a description of how the blood flows from the heart to the lungs to the rest of the body. Also, the following are helpful examples if you are more of a visual learner!

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The circulatory system is a system that brings freshly-oxygenated blood to all the tissues and organs of the body. When the heart contracts it causes a forceful tightening of the myocardium that pushes blood out into two major loops. The systemic loop brings oxygen to the organs, structures and tissues and collects carbon dioxide which much be removed from the body. The systemic loop carries oxygen fresh blood from the lungs that enters the superior left chamber of the heart; this is known as the left atrium. From here, the blood is forced, by contraction, through the bicuspid valve into the left ventricle. When the left ventricle contracts during a heartbeat, the blood on the left side is forced through the aortic semi-lunar valve into the aorta. The aorta sends oxygen-rich blood to every part of the body except the lungs. Because the body has an extensive amount of arteries and capillaries the left ventricle must produce a large enough contraction to give the blood enough pressure to make it to all the capillaries throughout the body and then back to the heart. This explains why the wall or myocardium of the left ventricle is much thicker than the right ventricle.



The pulmonary loop carries blood to and from the lungs and releases the carbon dioxide while picking up fresh oxygen. The pulmonary loop is controlled by the right side of the heart. After the blood has gone through the systemic loop, it returns to the heart through the superior vena cava and the inferior vena cava where veins enter the right atrium. The superior vena cava collects all the blood from the upper part of the body and inferior vena cava collects blood from the lower part of the body. Once in the right atrium, a contraction forces the oxygen-poor blood through the tricuspid valve into the right ventricle. When the right ventricle contracts, it forces the blood through the pulmonary semi-lunar valve and into the two pulmonary arteries which carry the blood to one of the two lungs. Once the oxygen has been “picked-up” and the carbon dioxide has been “dumped,” the blood flows back to the heart through the pulmonary veins where it enters the left atrium, thus started the process over.
The valves are needed because they prevent blood from flowing back into the chamber they came from. The muscle between the heart the splits it into a left and right side is known as the septum. The septum prevents oxygen-rich and oxygen poor blood from mixing.