What are the parts of the heart?
The parts of your heart are like the parts of a building. Your heart anatomy includes:
- Walls.
- Chambers that are like rooms.
- Valves that open and close like doors to the rooms.
- Blood vessels like plumbing pipes that run through a building.
- An electrical conduction system like electrical power that runs through a building.
Heart walls
Your heart walls are the muscles that contract (squeeze) and relax to send blood throughout your body. A layer of muscular tissue called the septum divides your heart walls into the left and right sides.
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Your heart walls have three layers:
- Endocardium: Inner layer.
- Myocardium: Muscular middle layer.
- Epicardium: Protective outer layer.
The epicardium is one layer of your pericardium. The pericardium is a protective sac that covers your entire heart. It produces fluid to lubricate your heart and keep it from rubbing against other organs.
Heart chambers
Your heart has four separate chambers. You have two chambers on the top (atrium, plural atria) and two on the bottom (ventricles), one on each side of your heart.
- Right atrium: Two large veins deliver oxygen-poor blood to your right atrium. The superior vena cava carries blood from your upper body. The inferior vena cava brings blood from your lower body. Then the right atrium pumps the blood to your right ventricle.
- Right ventricle: The lower right chamber pumps the oxygen-poor blood to your lungs through the pulmonary artery. The lungs reload the blood with oxygen.
- Left atrium: After the lungs fill your blood with oxygen, the pulmonary veins carry the blood to the left atrium. This upper chamber pumps the blood to your left ventricle.
- Left ventricle: The left ventricle is slightly larger than the right. It pumps oxygen-rich blood to the rest of your body.
Heart valves
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Your heart valves are like doors between your heart chambers. They open and close to allow blood to flow through. They also keep your blood from moving in the wrong direction.
Atrioventricular valves
The atrioventricular (AV) valves open between your upper and lower heart chambers. They include:
- Tricuspid valve: Door between your right atrium and right ventricle.
- Mitral valve: Door between your left atrium and left ventricle.
Semilunar valves
Semilunar (SL) valves open when blood flows out of your ventricles. They include:
- Aortic valve: Opens when blood flows out of your left ventricle to your aorta (artery that carries oxygen-rich blood to your body).
- Pulmonary valve: Opens when blood flows from your right ventricle to your pulmonary arteries (the only arteries that carry oxygen-poor blood to your lungs).
Blood vessels
Your heart pumps blood through three types of blood vessels:
- Arteries carry oxygen-rich blood from your heart to your body’s tissues. The exception is your pulmonary arteries, which go to your lungs.
- Veins carry oxygen-poor blood back to your heart.
- Capillaries are small blood vessels where your body exchanges oxygen-rich and oxygen-poor blood.
Coronary arteries
Your heart receives nutrients through a network of coronary arteries. These arteries run along your heart’s surface. They serve the heart itself and include the:
- Left coronary artery: Divides into two branches (the circumflex artery and the left anterior descending artery).
- Circumflex artery: Supplies blood to the left atrium and the side and back of the left ventricle.
- Left anterior descending artery (LAD): Supplies blood to the front and bottom of the left ventricle and the front of the septum.
- Right coronary artery (RCA): Supplies blood to the right atrium, right ventricle, bottom portion of the left ventricle and back of the septum.
Electrical conduction system
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Your heart’s conduction system is like the electrical wiring of a building. It controls the rhythm and pace of your heartbeat. Signals start at the top of your heart and move down to the bottom. Your conduction system includes:
- Sinoatrial (SA) node: Sends the signals that make your heart beat.
- Atrioventricular (AV) node: Carries electrical signals from your heart’s upper chambers to its lower ones.
- Left bundle branch: Sends electric impulses to your left ventricle.
- Right bundle branch: Sends electric impulses to your right ventricle.
- Bundle of His: Sends impulses from your AV node to the Purkinje fibers.
- Purkinje fibers: Make your heart ventricles contract and pump out blood.
Where is your heart located?
Your heart is in the front of your chest. It sits slightly behind and to the left of your sternum (breastbone), which is in the middle of your chest.
Your heart is slightly on the left side of your body. It sits between your right and left lungs. The left lung is slightly smaller to make room for the heart in your left chest. Your rib cage protects your heart.
What does your heart look like?
Your heart looks a little bit like an upside-down pyramid with rounded edges. Large blood vessels go into and out of your heart to bring blood into and away from your heart. They connect your heart to the rest of your body, which it supplies with blood and oxygen.
How big is your heart?
Everyone’s heart is a slightly different size. Generally, your heart is about the same size as your fist. On average, an adult’s heart weighs about 10 ounces. Your heart may weigh a little more or a little less, depending on your body size and sex.
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