The heart is a hollow organ made of muscle. The heart and blood vessels Biology of the Blood Vessels Blood vessels are hollow tubes like pipes that carry blood through your body. The blood delivers oxygen and nutrients to all parts of your body and removes waste products, such as carbon dioxide... read more are part of your cardiovascular system.
Every minute, your heart beats about 70 times and pumps about 1 gallon (4 liters) of blood. Your heart beats faster and pumps harder during exercise, when your body needs more oxygen. When you check your pulse, you're measuring your heart rate, or the number of beats per minute.
Blood traveling through your body delivers oxygen and nutrients to tissues and organs. Waste from those tissues and organs is carried by blood to the lungs and kidneys for removal from the body.
The heart is a pump for blood. It's actually 2 pumps connected together—one on the right side of the heart and one on the left side.
In order to pump blood, your heart has:
The heart has 4 compartments (chambers), two on the right and two on the left. The chambers of your heart relax, fill with blood, and then contract to pump the blood out.
Your heart has 4 valves that control the flow of blood. The valves open to let blood out of one chamber and into the next chamber or blood vessel. The valves close to keep blood from flowing backward into the wrong chamber.
When you put your head on someone's chest and listen to their heartbeat, you're hearing the sound of the heart valves opening and closing.
Your heart should always have a regular, rhythmic beat, like the ticking of a clock:
There are special pacemaker cells in a part of your heart called the SA node. The pacemaker cells have their own natural rhythm of 60 to 100 signals per minute. Nerves from your brain can send messages to the cells telling them to speed up or slow down.
Your heart's conduction system has tiny strips of tissue sort of like electrical wires. The conduction system carries the pacemaker signals to the rest of your heart. The conduction system includes a gateway called the AV node. The AV node controls how signals pass from the upper chambers of your heart (atria) to the lower chambers (ventricles). When the conduction system is working properly, the signals get to each of your heart muscle cells at just the right time. Your heart then gives a good, strong beat that pumps blood properly.
Tracing the Heart’s Electrical Pathway
Like all muscles, the heart needs a steady supply of blood to work. You might think that, because the heart is full of blood, it doesn't need a separate blood supply. However, blood that pumps through the heart doesn't feed the heart muscle. Instead the heart muscle is fed by its own blood vessels.
Coronary is a word for heart.
You can have problems with any part of your heart:
The muscles of the heart chambers can pump too weakly causing heart failure Heart Failure Your heart pumps blood to carry oxygen and nutrients to the rest of your body. Heart failure is when your heart doesn’t pump blood as well as it should. It doesn’t mean your heart has stopped... read more
In heart valve disorders Overview of Heart Valve Disorders Your heart is a muscle that pumps blood through your body. Your heart has four chambers. The atria are the two upper chambers in your heart—the right atrium and the left atrium. The ventricles... read more , a valve can become leaky and let blood flow backward in the heart
You can have an abnormal heart rhythm Overview of Abnormal Heart Rhythms Your heart is a muscle that pumps blood through your body. Your heart rate is how fast your heart beats. Your heart should always have a regular, rhythmic beat, like the ticking of a clock.... read more because of a problem with your heart's pacemaker or conduction system
Your heart's arteries can become blocked, called coronary artery disease Overview of Coronary Artery Disease (CAD) The heart is a muscle that pumps blood. Like all muscles, the heart needs a steady supply of blood to work. Blood that pumps through the heart doesn't feed the heart muscle. Instead the heart... read more , which can lead to a heart attack Heart Attack A heart attack is when blood flow to part of your heart is suddenly blocked and some of your heart muscle dies. Doctors use the term myocardial infarction to refer to a heart attack. Myocardium... read more