How Your Heart Works

Inside This Article
1.
Introduction to How Your Heart Works
Chambers and Valves
3.
Blood Flow
4.
Electrical System
5.
Blood Supply
6.
Lots More Information
7.
See all The Body articles
Everyone knows that the heart is a vital organ. We cannot live without our heart. However, when you get right down to it, the heart is just a pump. A complex and important one, yes, but still just a pump. As with all other pumps it can become clogged, break down and need repair. This is why it is critical that we know how the heart works. With a little knowledge about your heart and what is good or bad for it, you can significantly reduce your risk for heart disease.
Heart disease is the leading cause of death in the United States. Almost 2,000 Americans die of heart disease each day. That is one death every 44 seconds. The good news is that the death rate from heart disease has been steadily decreasing. Unfortunately, heart disease still causes sudden death and many people die before even reaching the hospital.
The heart holds a special place in our collective psyche as well. Of course the heart is synonymous with love. It has many other associations, too. Here are just a few examples:
have a heart - be merciful
change of heart - change your mind
to know something by heart - memorize something
broken heart - to lose love
heartfelt - deeply felt
have your heart in the right place - to be kind
cry your heart out - to grieve
heavy heart - sadness
have your heart set on - to want something badly Certainly no other bodily organ elicits this kind of response. When was the last time you had a heavy pancreas?
In this article, we will look at this important organ so that you can understand exactly what makes your heart tick.
The heart is a hollow, cone-shaped muscle located between the lungs and behind the sternum (breastbone). Two-thirds of the heart is located to the left of the midline of the body and 1/3 is to the right (see Figure 1).
Figure 1[Please note - Medical illustrations assume that the patient isfacing you so that the right and left correspond to the patient's right and left. That's why the left and right labels here seem backwards.]
The apex (pointed end) points down and to the left. It is 5 inches (12 cm) long, 3.5 inches (8-9 cm) wide and 2.5 inches (6 cm) from front to back, and is roughly the size of your fist. The average weight of a female human heart is 9 ounces and a male's heart is 10.5 ounces. The heart comprises less than 0.5 percent of the total body weight.
The heart has three layers. The smooth, inside lining of the heart is called the endocardium. The middle layer of heart muscle is called the myocardium. It is surrounded by a fluid filled sac call the pericardium.
Heart SoundsWhen someone listens to your heart with a stethoscope the sound is often described as lub-dub lub-dub. The first heart sound (lub) is caused by the acceleration and deceleration of blood and a vibration of the heart at the time of the closure of the tricuspid and mitral valves. The second heart sound (dub) is caused by the same acceleration and deceleration of blood and vibrations at the time of closure of the pulmonic and aortic valves.