OK, it's time for another science-y post. Usually, I take on something very relevant to my specialty---it's a helluva lot easier to write about stuff I already know. But some basics are just really cool, and worth exploring, even though I'll have to step a bit outside my comfort zone. In this case, it's the heart. Because I'm venturing a bit on the wild side, I consulted an expert, whose hot, hot science helped illuminate this topic.
If you've taken a basic biology course, you probably have some idea of how the human heart works, but understanding can be a bit deeper if we look at the heart through the lens of things that can go wrong.
The heart is one the most easily recognized and, yet, mysterious organs in the human body. Physicians of the Hippocratean school first described the valves of the heart in the 4th century B.C. Since, the heart has historically been described as the core of love,spirituality, intellect, and emotion. The heart was originally thought to be the source of conscious thought. The heart is a recognizable icon, source of stress for some of us who have witnessed friends and family with cardiovascualr disease, and a subject of poetry and song. However, to the physician and physiologist, the human heart is simply a pump whose primary purpose is the circulation of blood throughout the circulatory system. In fact, the majority of cardiac physiology and pathology (disease) can be easily demystified and understood by thinking of the heart as a mechanical pump.
Human heart, post-mortem obviously
The heart is a pump
The heart has one basic function -- to receive oxygen poor blood from the body, pump it to the lungs where it can be replenished with oxygen, and then pump it back to the body where that oxygen is needed.
If we sliced through the human heart we would find that it has four compartments or chambers. The top chambers, or atria (singular = atrium), receive the blood. The lower chambers, or ventricles, pump the blood.
Human heart from Gray's Anatomy showing the four chambered heart.
The following diagram illustrates how blood travels through the heart:
Image courtesy Isis the Scientist
- Oxygen poor blood returns from the body and enters the right atrium
- Oxygen poor blood passes from the right atrium to the right ventricle. The right ventricle then pumps the oxygen poor blood into the pulmonary artery. Sometimes people are confused by the pulmonary artery because most people think of arteries as having oxygen rich blood. The true definition of "artery" is any vessel that takes blood away from the heart.
- Oxygen poor blood from the pulmonary artery travels to the lungs where the oxygen is replenished.
- Oxygen rich blood returns from the lungs and enters the left atrium
- Oxygen rich blood passes from the left atrium into the left ventricle. The left ventricle then pumps oxygen rich blood into the aorta.
- Oxygen rich blood from the aorta is then circulated through out the body. The oxygen is utilized and the blood becomes oxygen poor. Return to step 1 and begin the cycle again.
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