Basic Anatomy of the Heart: How It Works
Your heart is a muscular organ that has many important functions. Its primary job is to pump blood throughout your body, carrying necessary oxygen to all your organs, tissues and cells.
In its simplest terms, you can think of the heart as the “central train station” in a major metropolis. It is a hub of activity where blood arrives and departs. It is part of the larger cardiovascular system, which includes circulating routes that deliver blood to the nearest and farthest neighborhoods of the body via arteries, and returns blood to the heart via the veins.
Read on to learn about the basic anatomy of the human heart.
The Heart Exterior
The fist-size, powerful organ is located slightly left of the middle of your chest, between your two lungs. (In fact, the heart and lungs work closely together as you’ll see in the right sidebar.)
The wall of the heart is made up of three tissue layers:
• Epicardium (outer, protective layer)
• Myocardium (middle, muscular layer)
• Endocardium (inner, thin layer)
The myocardium is the main muscle that acts as a pump for your body’s blood. It contracts and relaxes, creating your heartbeat. The contractions are initiated by an electrical signal from the sinoatrial node, known as your heart’s natural pacemaker.
The Two Circulation Systems of the Heart
Your heart is responsible for both pumping blood through the lungs, and throughout your body.
Pulmonary Circulation
The heart is located between the lungs for good reason. It allows these two major organs to synchronize their efforts, as each one depends on the other to do its work.
Pulmonary circulation is the term for the movement of blood from the heart into the lungs where carbon dioxide is released from the blood through your exhaled breath. Then, upon inhaling, your lungs pull in oxygen and bring it into the blood, which is then carried back to the heart’s left atrium.
Systemic Circulation
From the left atrium, the oxygen-rich blood flows into the lower left ventricle and out through the aorta to be distributed throughout the entire body via arteries and capillaries. The veins carry the blood back to the heart, where it completes its circulatory route.
A Look Inside the Heart
The Four Chambers
Your heart’s interior is divided into four chambers. Each chamber has its own function, yet all work together to circulate blood throughout the body.
Right atrium: Blood that is low in oxygen and high in carbon dioxide is collected in this right upper chamber, which then pumps the blood down to the right ventricle.
Right ventricle: This lower chamber pumps the oxygen-poor blood through the pulmonary artery to your lungs where it becomes oxygenated.
Left atrium: The pulmonary veins carry the oxygen-rich blood from the lungs to the left atrium. This upper chamber then pumps the blood to your left ventricle.
Left ventricle: This chamber pumps oxygen-rich blood out to the rest of your body.
Blood Vessels, Valves & Arteries
Four blood vessels lead into and out of the heart, and four valves act as gates, allowing the blood to move forward through the chambers and preventing backward flow.
Blood Vessels
Aorta is the largest artery in the body. It sends blood out to all the organs, tissues and cells. Vena cava is the largest vein in the body. It returns blood to the heart.
Pulmonary artery carries oxygen-poor blood to the lungs.
Pulmonary vein returns oxygenated blood from the lungs to the heart.
Heart Valves
Tricuspid valve opens to let blood flow between your right atrium and right ventricle.
Pulmonary valve opens to allow blood flow from your right ventricle into your pulmonary arteries.
Mitral valve opens between your left atrium and left ventricle.
Aortic valve opens from the left ventricle into the aorta, carrying oxygenated blood to your body.
The Importance of Coronary Arteries
The coronary arteries are major blood vessels that wrap around and inside the heart to supply the heart muscle with blood. The right and left coronary arteries are the largest, each of which divides into smaller branches.
It’s important to note, if any of these arteries are blocked with plaque, it could lead to a heart attack.