About the Heart

The Normal Heart

The heart consists of four chambers. The deoxygenated blood enters the heart into the Right Atrium via the inferior and superior vena cava. Then the blood is pumped into the lower chamber, the Right Ventricle from where it is pumped to the lungs via the pulmonary circulatory system where gaseous exchange can take place in the lungs.

Oxygenated blood from the lungs enters the heart again into the Left Atrium from where it passes into the Left Ventricle. From there, it is pumped into the aorta which is the major artery that branches off to supply the whole body with blood.

Note that every region of the heart that blood passes through is guarded by valves which prevent backflow, permitting only a one-way direction of blood.

A healthy heart will be able to pump blood efficiently to supply all the tissues in the body with blood, supplying sufficient amounts of nutrients and oxygen to meet the demands of the cells.

 

Coronary Arteries

Like any other muscle in the body, cardiac muscles require oxygen. This is supplied via the Coronary Arteries. These arteries branch off the aorta.

Immediately after passing the Aortic Valve, two branches off the aorta supply the myocardial blood - the left and right main coronary arteries.

The left coronary artery tends to be larger. It's divided into two further branches, known as the Left Anterior Descending coronary arteries, supplying the front, and Left Circumflex coronary arteries, supplying the left side and back. The heart receives about 5% of the total blood pumped through the aorta.

Venous return of the myocardial blood is collected into veins that join to form the Coronary Sinus, returning blood to the back of right atrium.

The structure of the wall of coronary arteries is same as any other artery in the body. There are three distinct layers of the arterial wall: the Tunica Intima (innermost), the Tunica Media (middle) and the Tunica Adventitia (outermost).

The intima consists of a lining of squamous endothelial cells. The intima also contains extracellular matrix (Collagen and proteoglycans). Separating the intima and media is the Internal Elastic Lamina (IEL).

The media is a thicker layer consisting of smooth muscle cells, with surrounding elastin. The External Elastic Lamina (EEL) separates the media and adventitia.

The adventitia, often considered the outer covering, joins the artery with surrounding tissue. It is comprised of connective tissue with fibroblasts, few nerve fibres and some smooth muscle cells.

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