Heart Power

And The Mechanics Behind Each Beat

Sarah E. Wilson

What is the Heart?

The heart is a hollow, muscular organ located within the chest cavity and slightly left of the breastbone. The size of the heart is comparable to a clenched fist and its main function is to pump oxygenated blood throughout the body, helping to maintain internal balance.

Basic Anatomy of the Heart

The heart is composed of:
1. Four Chambers
  • Right Atrium, Right Ventricle, Left Atrium, Left Ventricle
2. Two Atria
  • Right Atrium and Left Atrium
3. Two Atrioventricular Valves
  • Tricuspid Valve and Mitral (Bicuspid) Valve
4. Two Ventricles
  • Right Ventricle and Left Ventricle
5. Two Semilunar Valves
  • Pulmonary Valve and Aortic Valve

Pathway of Blood through the Heart

Deoxygenated blood enters the heart through the superior or inferior vena cava; blood from the upper half of the body travels through the superior vena cava, while the inferior vena cava collects blood from the lower portion of the body. From here, blood travels into the right atrium. The pathway is as follows:
  • Superior or Inferior Vena Cava > Right Atrium >
  • Tricuspid Valve > Right Ventricle >
  • Pulmonary Valve > Pulmonary Trunk >
  • Pulmonary Artery > Lungs for oxygenation

Once blood becomes oxygenated within the lungs, this newly oxygenated blood is sent back to the heart to be transported throughout the body. The pathway from the lungs back to the heart and body includes:

  • Lungs > Pulmonary Veins >
  • Left Atrium > Mitral Valve >
  • Left Ventricle > Aortic Valve >
  • Aorta > Throughout the Body
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Electrical Conduction System

The heart relies on a continuous electrical impulse that causes alternating contractions and relaxations of the heart's chambers; these impulses open and close heart valves while pushing blood throughout the heart and preventing backflow. Each cycle of contraction and relaxation of the heart's chambers is represented by a heartbeat. Each heartbeat has two phases:

  • diastole
  • systole

The atria and ventricles relax and fill with blood during diastole, while systole represents the contractions of the atria and ventricles; as the atria contract, blood is pumped into the ventricles and blood from the ventricles is pumped out of the heart.

How do Electrical Impulses Travel through the Heart?

The electrical conduction system of the heart is composed of the following parts:
  1. Sinoatrial Node (SA Node)
  2. Atrioventricular Node (AV Node)
  3. Bundle of His
  4. Purkinje Fibers
  • A cranial nerve, called the vagus nerve, stimulates the SA Node and signals for the right and left atria to begin filling with blood. This impulse causes a contraction of the atria, pushing blood through the valves and into the right and left ventricles
  • The signal then arrives at the AV Node as the right and left ventricles begin to fill with blood
  • From here, the signal travels along the Bundle of His and separates into left and right bundle branches through the Purkinje fibers
  • As the signal spreads throughout the ventricle walls, the left ventricle contracts, pushing blood through the aortic valve and into the rest of the body
  • The right ventricle then contracts, causing blood to flow through the pulmonary artery and into the lungs
  • The ventricles then relax and the cycle is repeated
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Heart Healthy Tips

In order to maintain proper functioning of the heart, there are several adjustable factors that may prevent future malfunctioning of the heart. Some modifiable factors include:
1. Maintain A Low-Fat Diet
  • lean cuts of meat, low-fat and fat-free dairy products
2. Add Fiber-Rich Foods
  • fruits, vegetables, whole-grain cereals and breads, black beans
3. Cut Cholesterol
  • Limit meat, poultry, dairy products, eggs per day
4. Maintain Regular Checkups
  • Annual physicals to check blood pressure and blood work, including cholesterol levels, indicate whether or not additional measures are needed to control factors associated with heart health