Comprised of muscle, the organ we call the heart beats approximately 100,000 times a day and pumps over 1.5 million gallons of blood through the circulatory system every year. The heart has two atria and two ventricles---chambers that house the incoming and outgoing blood. It takes the synchronized effort of its four chambers and the help of the lungs to properly carry out this awesome task.
Role of the Right Atrium
Blood comes into the right atrium via both the superior and inferior vena cava veins. Void of oxygen, this blood comes back to the heart after delivering oxygen to the brain and other body organs. As it comes into the right atrium it prepares to "recycle" through the heart, replenish its oxygen supply and start its delivery job again.
Role of the Right Ventricle
Once in the right atrium the chamber contracts and the mitral valve, between the right atrium and the right ventricle, opens and sends the blood into the right ventricle. The load of blood in the right ventricle then gets expelled via the pulmonary semilunar valve into the pulmonary arteries.
Role of the Pulmonary System
The blood moves along and enters the lungs where it picks up oxygen. On its return to the heart, it re-enters at the pulmonary semilunar valve and flows from the pulmonary vein into the left atrium. Ordinarily arteries carry oxygenated blood and veins carry deoxygenated blood.
Role of the Left Atrium
Now in the left side of the heart, the oxygen-rich blood prepares to enter the left ventricle. As the tricuspid valve opens the atrium contracts and sends its contents on to the ventricle. The tricuspid valve has three leaves or cusps whereas the mitral valve on the right side of the heart only has two.
Role of the Left Ventricle
The left ventricle has the formidable job of shooting the oxygenated blood out into the circulatory system where the arteries transport the life-giving nutrition to the body's organs. When it contracts it does so with great force. According to "Gray's Anatomy," the left ventricle's size ratio to the right ventricle is 3 to 1 and it has thicker walls. The left ventricle occupies a large part of the posterior side of the heart.
References
- Human Anatomy, 2nd ed.; Frederic H. Hartini, Ph.D. and Michael J. Timmons, M.S.; 1997
- Gray's Anatomy, unabridged edition, Henry Gray, F.R.S.; 1974
