The Normal Heart
The heart is a hollow, muscular organ, about the size of a fist. It is located in the left center of the chest, beneath the sternum (breastbone). The heart's function is to pump blood containing oxygen and nutrients to all parts of the body.
The heart consists of four chambers. The upper two chambers are referred to as the atria, while the lower two chambers are called ventricles. Four valves with the heart assist in directing blood flow. A wall called the septum divides the left and right sides of the heart.
Oxygen poor blood enters the right side of the heart through two large veins called the superior and inferior vena cava. Blood travels into the right atrium through the tricuspid valve, into the right ventricle, and throught the pulmonic valve to the lungs. The blood receives oxygen from the lungs and lows to the left side of the heart, into the left atrium, through the mitral valve and into the left ventricle. The blood then flows through the aortic valve, the large artery called the aorta, and then to all parts of the body.
Contraction of the heart occurs normally about 60 to 100 times per minute and is counted as the pulse.
Coronary Arteries
Like all organs, the heart requires both oxygen and nutrients. Although the chambers of the heart are full of blood, the heart muscle itself receives no nourishment from this blood. The coronary arteries, which originate from the bottom of the aorta, bring blood to the heart muscle. The left coronary artery begins as a short portion, called the left main, and divides into the left anterior descending (supplying blood to the front of the heart), and the left circumflex (supplying blood to the left side and back of the heart). The right coronary artery feeds the right side of the heart and has branches that extend to the bottom.Electrical System of the Heart
The heart's electrical system normally begins within specialized tissue in the heart, called the sinus node. Electrical signals travel along a pathway, through the heart, and result in contraction. The signal can be recorded on an electrocardiogram, or ECG.Next: Coronary Artery Disease