Myocardium: Definition & Function

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  • 0:01 A Silent Condition
  • 0:28 What Is the Myocardium?
  • 0:52 How Does It Work?
  • 1:43 Diseases of the Myocardium
  • 2:50 Lesson Summary
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Lesson Transcript
Instructor: Kara Jones
Understand the definition of myocardium, and explore its functions and physical makeup. Then, read about some conditions that can affect this unique type of muscle.

A Silent Condition

Meet Joe. He is 46 years old and has been healthy his entire life, with the exception of a few colds and the normal childhood illnesses. Joe does not smoke, he exercises three times a week, and tries to eat a healthy diet. Joe feels great and is totally unaware that he suffers from a condition that can cause a heart attack at any time. The condition is cardiomyopathy, a disease of the myocardium.

What Is the Myocardium?

The myocardium is the thick, middle layer of the heart and is composed of cardiac muscle. Cardiac muscle is very unique because it possesses the characteristics of skeletal muscle AND smooth muscle. Skeletal muscle controls the voluntary movement of the body, while smooth muscle is responsible for the movement of all other body organs. The myocardium acts on its own, with no conscious effort.

How Does It Work?

The myocardium is composed of thousands of muscle fibers that are striated (they have multiple striped fibers) and are arranged at irregular intervals throughout the muscle. They connect to each other at points called intercalated discs. These are tiny membranes that separate the ends of the muscle cells. These fibers actually use calcium to cause an electrical conduction to occur.

The contraction (heart beat) of the myocardium is responsible for pumping blood with oxygen to the body. The body requires oxygen for proper function. The heart muscle also pumps deoxygenated blood into the lungs, allowing for replacement of the oxygen so it can be used again. Like all body tissues, the myocardium itself requires a blood supply in order to function; the coronary arteries supply the heart muscle with blood.

Diseases of the Myocardium

The myocardium is obviously integral to having a healthy, working body. When it is unable to function properly, serious conditions can arise -- like the 'silent condition' mentioned earlier.

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