Blood Flow Through the Heart by Karissa Willard

The heart is an integral muscular organ and a vital part of the human cardiovascular system. It provides the human body with a continuous flow of blood, which in turn provides cells with a continuous circulation of oxygen and nutrients, and transports waste away from those same cells. Blood cells, specifically red blood cells are the actual vehicles providing this life-sustaining transportation. The cells are suspended in blood plasma, which is mainly comprised of water and minute traces of minerals, sugars (glucose), and proteins. The human heart is to the body what an internal combustion engine is to an automobile, and as an automobile, its structure and mechanics are designed to do one thing, keep everything moving.

Our heart is about the size of a closed fist, between 230 and 350 grams in mass. The human heart and blood start to flow through the human body after about 21 days following conception. From this day to the day it stops it will have beat almost 3 billion times. This beautiful organic machine is a complex muscular pump, which keeps us alive and active. Our heart and blood are key to human athleticism, and activity altogether.

The heart’s structure is fairly simple; it is comprised of 4 chambers. The heart itself is a layered muscular miracle. Three layers comprise the outer and inner walls of the heart, the first being the epicardium, the second the myocardium, and lastly the endocardium. The myocardium is the muscle, which contracts and helps to pump blood into and out of the heart. The chambers are split into 2 upper chambers called atria (left and right), and 2 lower chambers called ventricles (left and right). The left and right atriums serve a different purpose than those of the left and right ventricles. In between this party, separating the left and right sides is a thick muscle called the Septum. This divides the left atrium and ventricle from their right counterparts.

The heart is placed in between the lungs slightly skewed to the left just because of its position and functions. Blood comes to the Inferior or Superior vena cava and pours into the right atrium; it then starts to fill up the right atrium and passes through the tricuspid valve and into the right ventricle. The tricuspid valve then shuts closed so the blood cannot go back up into the right atrium. Our blood tends to rush back to the right atrium due to the pressure in the right ventricle. The tricuspid valve prevents this from happening because blood is forced to move from high to low blood pressure. The blood leaves the right ventricle and goes out into the pulmonary semilunar valve where it then travels into the pulmonary arteries. The pulmonary semilunar valves shut so blood can’t flow back. The blood in the pulmonary arteries then moves to the lungs and fills the lungs. Blood leaves the lungs flows through the pulmonary veins and enters the left atrium. Blood then fills up the left atrium and flows through the bicuspid valve into the left ventricle. The bicuspid valve then closes shut so the blood cannot flow back up to the left atrium because this too like the right side has a lot of pressure and the blood wants to move back. But blood must flow from a high to a low pressure. Blood fills the left ventricle and leaves out of the aortic semilunar valve and up the aorta. The aortic semilunar valve also closes shut so blood can’t back flow. Blood then goes up the ascending aorta to the aortic arch to the body tissue.