Learning More About Your Heart
How Your Heart Works
The heart is a muscle about the size of your fist. It moves blood, oxygen, and nutrients through the body.
How Blood Flows Through the Heart
The heart has four chambers (figure 1). The top two chambers are called the right and left atrium and the bottom two chambers are called the right and left ventricles. The heart also has four valves that open and close to prevent backward blood flow.
Blood moves through the body in four stages.
- It first flows into the right side of the heart
- It is then pumped to the lungs to pick up oxygen.
- The blood returns to the left side of the heart.
- Finally, it is pumped to the body through the aorta and other arteries
Heart Valves
The heart has four valves, one between each of the chambers
- The tricuspid valve separates the right atrium and the right ventricle.
- The pulmonic valve controls blood flowing from the right ventricle to the lungs.
- The mitral (bicuspid) valve is between the left atrium and the left ventricle.
- The aortic valve controls blood flowing from the left ventricle to the aorta and the body.
When the pulmonic and aortic valves are open, the tricuspid and mitral valves must be closed. Similarly, when the tricuspid and mitral valves are open, the pulmonic and aortic valves must be closed. This process keeps blood moving forward.
Electrical System
An automatic electrical system in the heart causes the heart beat. A normal rhythm is called “normal sinus rhythm”. A typical resting heart rate is 60-100 beats per minute.
Normal heart beats start in the SA node (figure 2). The SA node sends a signal that travels through the upper part of the heart, making the atrium contract.
The signal then goes to the AV node, where it is sent out to the rest of the heart, causing the bottom part of the heart (ventricle) contract.
