Parts of the Heart
Your heart has four main chambers that blood flows through. The right atrium receives oxygen-poor blood from the body through the superior and inferior vena cava, which then passes through the tricuspid valve into the right ventricle. From there, blood flows through the pulmonary valve into the pulmonary arteries to your lungs for oxygenation.
On the left side, the left atrium receives oxygen-rich blood from the lungs via pulmonary veins. This blood passes through the mitral valve (also called the bicuspid valve) into the left ventricle, which pumps it through the aortic valve into the aorta to supply your entire body. The mitral and tricuspid valves are called atrioventricular valves because they sit between the atria and ventricles.
The heart wall itself has three distinct layers. The innermost layer is the endocardium, which directly contacts blood. The middle and thickest layer is the myocardium, which contains the powerful contractile muscles that pump blood. The outer layer, the pericardium, has two parts: the visceral pericardium (inner layer) and parietal pericardium (outer layer), with fluid between them that allows the heart to beat without friction.
Fun Fact: The papillary muscles inside your heart send string-like structures called chordae tendineae to prevent the heart valves from flipping backward. They're like little lifelines that keep your blood flowing in the right direction!
