Contact for Patients

Your heart, your circulation and how they function

The heart is a hollow muscular structure that is approximately the size of a fist. In one minute, it pumps about five quarts (roughly five liters) of blood through the body. To do this work, the healthy heart beats between 60 and 100 times. During physical exercise or under emotional stress, the heartbeat can increase to more than 100 beats per minute to supply the organs and tissues in the body with a sufficient amount of oxygen.

The heart is made up of four chambers. A wall, called the septum, separates the left and right sides.

Both halves of the heart have an atrium and a ventricle, each of which is hollow. The atrium is the top chamber, which connects to the main pumping chamber of the heart called the ventricle.

The right side of the heart pumps already used, dark red blood into the lungs. After the blood that traveled through the body has been enriched with oxygen in the lungs, it flows to the left half of the heart. The left side of the heart pumps regenerated, bright red blood into the main artery, the aorta, which supplies the body with oxygen.

The heart has one-way valves, called heart valves, which open when blood is flowing through them and then close, preventing blood from flowing backwards.

There are two types of valves:

• Atrioventricular valves 
  (a mitral valve on the left side and a tricuspid valve on the right side)
• Semilunar valves
  (an aortic valve on the left side and a pulmonary valve on the right side)

The atrioventricular valves separate the ventricles from the atria. Whenever the atria contract, these valves open, thus allowing blood to flow into the ventricles. Whenever the ventricles contract, these valves close, preventing the blood from flowing back into the atria.

The semilunar valves separate the ventricles from the blood vessels leaving the heart. Whenever the ventricles contract, these valves open, allowing blood to move in a forward direction. Whenever the ventricles relax, these valves close and, as a result, prevent blood from flowing back into the heart.

The closure of heart valves results in sounds that can be heard by a doctor using a stethoscope. The first heart sound occurs as a result of the closure of the atrioventricular valves, while the second heart sound results from closure of the semilunar valves. Abnormalities in the heart valves, such as thickening or excessive floppiness resulting in a change in the flow across the valve, may result in a sound called a murmur.