What is a Heartbeat?

The heart is the centerpiece of the human circulatory system. The heart is a fist-sized muscle located just left-of-center in the chest. Its primary job is to pump blood throughout the body to deliver the oxygen and nutrients necessary for daily life. During each beat, a complex set of actions occurs to make this feat possible.

Basic Anatomy of the Heart

The human heart has four chambers. The upper two chambers are the atria. The atria receive blood from the body and the lungs. The lower two chambers are the ventricles. These chambers pump oxygenated blood to the body and deoxygenated blood to the lungs.

Arteries and Veins

A basic understanding of arteries and veins is important for understanding how the heart works. Collectively called blood vessels, KidsHealth.org explains that the arteries and veins are the tubing in which blood circulates throughout the body. Arteries carry the blood away from the heart, providing oxygen and nutrients to the body. Veins carry the deoxygenated blood back to the heart.

The Lungs

The lungs play a vital role in each heartbeat. The American Heart Association explains that the deoxygenated blood is pumped to the lungs from the right ventricle and through the pulmonary artery. The blood receives oxygen from the lungs and returns to the heart through the pulmonary vein, the only vein to return oxygenated blood to the heart. Upon its return, the freshly oxygenated blood is pumped to the rest of the body.

Blood’s Journey

Blood travels a specific path during each heartbeat. The American Heart Association explains the flow follows the body-heart-lungs-heart-body path, a cycle which repeats with each beat. During the resting phase of the heartbeat, the atria fill with blood.

The right atrium receives the deoxygenated blood as it returns from the body. The left atrium receives the freshly oxygenated blood from the lungs. The heart pumps out blood during its forceful contractions. With each contraction, the blood from the right atrium flows to the lungs, while the oxygen-rich blood in the left atrium is delivered to the body.

The “Lub-Dub” of a Heartbeat

During a physical exam, doctors and nurses listen to the sounds the heart makes with an instrument called a stethoscope. The sound is known as the “lub-dub,” a term derived from the sound the blood makes as it travels through the heart during each beat. KidsHealth.org explains that the “lub” is heard when the doors, known as the valves, between the atrium and the ventricles close during each beat. The “dub” is heard when the aortic and pulmonary valves close when blood is pumped out of the heart.



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