How many atriums does the human heart have

But how exactly does the heart work? There are four chambers in the heart that together function as a two-sided pump.

The left side of the heart pumps blood out into the body through the arteries, while the right side of the heart collects blood through the veins. The top chambers of the heart are called the left atrium and right atrium.

The bottom chambers of the heart are the left ventricle and right ventricle, which have thicker walls. The heart itself needs oxygen-rich blood to function, which is supplied by the coronary arteries running along its surface. A double-layered sac called the pericardium surrounds the heart, with the inner layer attached to the heart muscle and the outer layer attached by ligaments to your spinal column, diaphragm, and other parts of the body.

Fluid between the two layers of the pericardium allows it to move as the heart beats. It splits into two main branches, and brings blood from the heart to the lungs.

At the lungs, the blood picks up oxygen and drops off carbon dioxide. The blood then returns to the heart through the pulmonary veins. In systemic circulation: Next, blood that returns to the heart has picked up lots of oxygen from the lungs. So it can now go out to the body. The aorta is a big artery that leaves the heart carrying this oxygenated blood. Branches off of the aorta send blood to the muscles of the heart itself, as well as all other parts of the body.

Like a tree, the branches gets smaller and smaller as they get farther from the aorta. At each body part, a network of tiny blood vessels called capillaries connects the very small artery branches to very small veins.

The capillaries have very thin walls, and through them, nutrients and oxygen are delivered to the cells. Waste products are brought into the capillaries. Capillaries then lead into small veins. Small veins lead to larger and larger veins as the blood approaches the heart. Valves in the veins keep blood flowing in the correct direction. Two large veins that lead into the heart are the superior vena cava and inferior vena cava. The terms superior and inferior don't mean that one vein is better than the other, but that they're located above and below the heart.

Once the blood is back in the heart, it needs to re-enter the pulmonary circulation and go back to the lungs to drop off the carbon dioxide and pick up more oxygen. How Does the Heart Beat? This is when the ventricles contract and pump blood into the aorta and pulmonary artery.

During systole, the atrioventricular valves close, creating the first sound the lub of a heartbeat. When the atrioventricular valves close, it keeps the blood from going back up into the atria. During this time, the aortic and pulmonary valves are open to allow blood into the aorta and pulmonary artery. When the ventricles finish contracting, the aortic and pulmonary valves close to prevent blood from flowing back into the ventricles. These valves closing is what creates the second sound the dub of a heartbeat.

The second phase is called diastole die-AS-tuh-lee. Please turn on JavaScript and try again. Main Content. Important Phone Numbers. Top of the page. The right atrium receives oxygen-poor blood from the body and pumps it to the right ventricle. The right ventricle pumps the oxygen-poor blood to the lungs. The left atrium receives oxygen-rich blood from the lungs and pumps it to the left ventricle.