About the heart

The heart is the key to the body's cardiovascular system. It is responsible for pumping blood throughout the body, delivering oxygen and nutrients to every cell and removing carbon dioxide and waste products made by those cells. Oxygen-rich blood moves through the body via a network of arteries. Oxygenpoor blood returns to the heart through veins.

Four chambers

The heart has four chambers. The upper chambers are called the left and right atria, and the lower ones are the left and right ventricles. They are separated by a wall of muscle called the septum.

With each beat, the heart achieves two goals simultaneously: it pushes blood to the lungs, where cells pick up oxygen; and it pumps already-oxygenated blood to the rest of the body.

Blood destined for the lungs passes through the right atrium and ventricle and then through the pulmonary arteries on the right side of the heart.

The oxygenated blood then travels from the lungs to the left side of the heart via the pulmonary veins. It enters the left atrium and then the left ventricle before being pushed out to the rest of the body.

When the heart beats

The heartbeat begins with an electrical impulse in a collection of cells in the right atrium, called the sinus node (SA node).

The impulse spreads through the heart, causing the right and left atria to contract, forcing the blood in these chambers into the ventricles. The signal then reaches an electrical connection between the atria and the ventricles, called the AV (atrio-ventricular) node.

When the ventricles fill with blood, the AV node sends the signal to the lower ventricles, causing them to contract, pumping blood through the rest of the body.

Source: Adapted from the Heart and Stroke Foundation of Canada

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	About Wave Wave is published six times a year by the Winnipeg Health Region in cooperation with the Winnipeg Free Press. It is available at newsstands, hospitals and clinics throughout Winnipeg, as well as McNally Robinson Books. Read the Summer 2010 issue of Wave