The Heart's Structure and Function
Your heart has four chambers that work as two separate pumps. The right atrium and ventricle handle deoxygenated blood, while the left atrium and ventricle manage oxygenated blood. A wall called the septum separates these two sides, preventing mixing.
Blood travels through your heart along a specific path. Deoxygenated blood enters the right side via the superior vena cava, then gets pumped to your lungs through the pulmonary arteries. After picking up oxygen, blood returns to the left atrium via pulmonary veins before being pumped out to your body through the aorta.
The heart contains four valves that ensure blood flows in one direction: the tricuspid and bicuspid (atrioventricular valves) between atria and ventricles, and the aortic and pulmonary (semilunar valves) leading out of the ventricles.
Did you know? The familiar "lub-dub" heartbeat sound comes from your valves closing - the "lub" is the atrioventricular valves shutting when your ventricles contract, while the "dub" is your semilunar valves closing.
Coordinating the Heartbeat
Your heart beats through a three-step process controlled by electrical signals. First, atrial systole occurs when the sino-atrial node triggers your atria to contract. Next comes ventricular systole, when the atrioventricular node causes your ventricles to contract. Finally, diastole happens when all chambers relax.
Blood pressure measures the force exerted on artery walls, recorded as two numbers. The higher number (normally around 120 mmHg) is systolic pressure - when your heart contracts. The lower number (normally around 80 mmHg) is diastolic pressure - when your heart relaxes between beats.
