Coronary Artery Disease

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Coronary artery disease is a life threatening condition that affects millions of people. It was one of the leading causes of death in America. Also known as artherosclerotic heart disease, this is the condition of an accumulation of plaque along the arterial walls that supply the myocardium, or muscles of the heart. The most common symptom of CAD is chest pain which is caused by the heart not getting enough blood. Fatigue and shortness of breath are also common symptoms. There are several ways to treat CAD. Consuming a small dosage of aspirin daily thins the blood and prevents clots in the arteries. This is important because the arterial walls have become narrow from the plaque build up making the passage of blood very difficult. Plaque is made up of fat, cholesterol, calcium and other substances that are found in the blood. Over time, the lack of oxygen supplied to the heart muscles can cause heart failure. Smokers have a much greater chance of plaque build up then non smokers. CAD is diagnosed in several ways. Electrocardiograms are done to check the flow of electricity through the heart, blood work is done to check cholesterol levels and a stress test is done to check the hearts ability to maintain homeostasis under extreme physical stress. Other then taking aspirin to thin the blood, other medications are offered and prescribed to prevent the continual thickening of the arteries.

The Coronary Arteries

In addition to the heart having pathways to supply the entire body with nutrients and oxygen, it also supplies itself with the oxygenated blood. The heart is composed of muscles and therefore needs to same amount of oxygen and proteins as the rest of the muscles in the body. The coronary arteries supply the heart with what it needs to stay functional. There are two main coronary arteries which branch from the Aorta. The right coronary artery supplies the right atrium and the right ventricle along with the bottom half of both ventricles and the back of the septum. The entire right side of the heart is supplied by the right coronary artery. The left coronary artery supplies blood to the circumflex artery which sends it to the left atrium and side and back of the left ventricle. It also moves from through the left anterior descending artery which supplies the front and bottom of the left ventricle and the front of the septum.

Divisions of the Heart

The human heart is divided into four main chambers. The right and left atrium and the right and left ventricle work together to pump blood throughout the body and supply nutrients and oxygen to all organs. Blood flows into the heart through the superior vena cava into the right atrium. The right atrium is larger then the left atrium and has much thinner muscle walls due to its stronger need to pump the blood further in the body then any other compartment of the heart. The blood that flows into the heart from the vena cava is blood that has already traveled through the body and dispersed nutrients and oxygen to the organs. The blood then travels through the coronary sinus and tricuspid valve into the right ventricle. The right ventricle pumps the blood out of the heart and into the lungs in order to be re oxygenated. Once the blood has traveled through the lungs and has been resupplied of oxygen it then travels through the pulmonary veins back to the heart into the left atrium. The left atrium is much smaller then the right atrium because it does not need as much strength to pump the blood through the body. Once the left atrium fills with blood, the bicuspid valve opens in a one way direction and allows the blood to flow into the left ventricle. The left ventricle then contracts and sends the blood out of the heart and into the rest of the body. The blood travels the full extent of the body through the arteries and capillaries and passes into the veins which return the blood back into the heart to start the cycle over again. The heart pumps the blood in this continuous cycle to keep the body alive.

Anatomy of the human heart

The human heart is an extraordinary organ that is the vital component to life. It is primarily a pump that moves blood throughout the entire body. Composed of four sections contained in the size of a fist, the heart pumps approximately seventy two beats per minute. Blood carries vital nutrients and proteins throughout the body and carries away wastes that have been removed from cells and organs back into the blood stream to be removed from the body. Without the continuous pump of blood, body organs will begin to shut down and soon after the discontinuation of blood supply, will die. The heart contracts and expands to control the movement of blood. The heart pumps at an "all or nothing" rate. Each beat is with full force of the organ. Once the blood has left the heart and traveled the full extent of the body it is returned back into the heart to be re oxygenated again. Once the blood has been oxygenated, it makes the travel through the body again in a continuous cycle. During this cycle, the heart rests only for about four tenths of a second.

Smallest pathway to and from the heart

The human body depends on capillaries as a route for blood to transport oxygen and carbon dioxide along with other nutrients and wastes to and from the lungs and heart. The capillaries are the smallest blood vessel in the body at only 5-10 microns in diameter. The lumen, or the center opening which allows the flow of blood, is only the width of a single red blood cell. The human body contains billions of capillaries in three different forms.

The most common capillary is the continuous capillary which supplies the skin and muscles. Its endothelium cells are in a continuous wall around the lumen of the capillary and are met by tight junctions between cells. Where a tight junction is not present between endothelium cells there is an intercellular cleft. Water and small ions are able to pass through the intercellular clefts into the skin and muscles. Pinocytotic vesicles run the length of the endothelium cells and supply the capillary with nutrients. Pericytes on the exterior of the basement membrane are large and cover an outstanding amount of the capillary.

The endocrine system, kidneys and pancreas contain fenestrated capillaries. These capillaries contain the same basement membrane and endothelium cells as the continuous capillary, however they contain small pores, fenestrations, within the endothelium which allow passage of small molecules and a trace amount of protein in and out of the capillary.

The last of the capillary types is called a sinusoid or discontinuous capillary. Although there are similarities between a sinusoid and the other types of capillaries, it is very distinctive. There are very large intercellular clefts within the capillary walls that split the basement membrane and endothelium cells far apart. The liver, spleen and bone marrow contain discontinuous capillaries. These large openings allow larger molecules and even blood cells to pass through the capillary walls. In the liver, macrophages are present on the exterior of the capillary which allow the destruction of foreign materials. The spleen has phagocytes present outside the capillary walls with extensions that reach through the intercellular clefts into the capillary to destroy foreign materials and prevent them from flowing through the blood stream and throughout the entire body. Each type of capillary is adapted for the type of tissue in which is accommodating.