Anatomy & Physiology 2 - Heartbt | Heart Disease | Heart Surgery | Chest Pains | Bypass

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Anatomy & Physiology 2

The Heart

Blood Circulation Through The Heart

  • The right atrium receives blood that has completed a tour around the body and is depleted of oxygen and other nutrients. This blood returns via 2 large veins: the superior vena cava returning blood from the head, neck, arms, and upper portions of the chest, and the inferior vena cava returning blood from the remainder of the body.   

  • The right atrium pumps this blood into the right ventricle, which, a fraction of a second later, pumps the blood into the blood vessels of the lungs.   

  • The lungs serve 2 functions: to oxygenate the blood by exposing it to the air you breathe in (which is 20% oxygen), and to eliminate the carbon dioxide that has accumulated in the blood as a result of the body's many metabolic functions.   

  • Having passed through the lungs, the blood enters the left atrium, which pumps it into the left ventricle.   

  • The left ventricle then pumps the blood back into the circulatory system of blood vessels (arteries and veins). The blood leaves the left ventricle via the aorta, the largest artery in the body. Because the left ventricle has to exert enough pressure to keep the blood moving throughout all the blood vessels of the body, it is a powerful pump. It is the pressure generated by the left ventricle that gets measured when you have your blood pressure checked.   

The heart, like all tissues in the body, requires oxygen to function. Indeed, it is the only muscle in the body that never rests. Thus, the heart has reserved for itself its own blood supply.  

  • This blood flows to the heart muscle through a group of arteries that begins less than one-half inch from where the aorta begins. These are known as the coronary arteries. These arteries deliver oxygen to both the heart muscle and the nerves of the heart.   

  • When something happens so that the flow of blood through a coronary artery gets interrupted, then the part of the heart muscle supplied by that artery begins to die. This is called coronary heart disease, or coronary artery disease. If this condition is not stopped, the heart itself starts to lose its strength to pump blood, a condition known as heart failure.   

  • When the interruption of coronary blood flow lasts only a few minutes, the symptoms are called angina, and there is no permanent damage to the heart. When the interruption lasts longer, that part of the heart muscle dies. This is referred to as a heart attack (myocardial infarction).   

• The Coronary Arteries
The four heart valves include the following:
The heart muscle, like every other organ or tissue in your body, needs oxygen-rich blood to survive. Blood is supplied to the heart by its own vascular system, called coronary circulation.
The aorta (the main blood supplier to the body) branches off into two main coronary blood vessels (also called arteries). These coronary arteries branch off into smaller arteries, which supply oxygen-rich blood to the entire heart muscle.
The right coronary artery supplies blood mainly to the right side of the heart. The right side of the heart is smaller because it pumps blood only to the lungs.

The left coronary artery, which branches into the:  

Circumflex artery (Cx)

The circumflex artery branches off the left coronary artery and encircles the heart muscle. This artery supplies blood to the back of the heart.  

Left anterior descending artery (LAD)

The left anterior descending artery branches off the left coronary artery and supplies blood to the front of the heart.

Smaller branches of the coronary arteries include: acute marginal, posterior descending (PDA), obtuse marginal (OM), and diagonals.

The left side of the heart is larger and more muscular because it pumps blood to the rest of the body. Additional arteries branch off the two main coronary arteries to supply the heart muscle with blood.  


Nerves of the heart: The heart's function is so important to the body that it has its own electrical system to keep it running independently of the rest of the body's nervous system.  

  • Even in cases of severe brain damage, the heart often beats normally.   

  • An extensive network of nerves runs throughout all 4 chambers of the heart. Electrical impulses course through these nerves to trigger the chambers to contract with perfectly synchronized timing much like the distributor and spark plugs of a car make sure that an engine's pistons fire in the right sequence.  

The ECG records this electrical activity and depicts it as a series of graph-like tracings, or waves. The shapes and frequencies of these tracings reveal abnormalities in the heart's anatomy or function.

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