A. Name and describe the function of each structure included onthe human body.

Blood is composed of a liquid called plasma and blood solids. Blood solids include erythrocytes, white blood cells, and platelets. Plasma makes up for 55% of blood, white blood solids fill in the remaining 45%. Plasma is a sticky yellow colored liquid that is about 90% water. Plasma carries dissolved substances which nourish cells. These substances, vitamins, minerals, amino acids, and glucose are absorbed from the digestive system and carried to the cells. They are distributed throughout the body so that cells may function properly. Plasma also carries hormones and brings wastes to the kidneys or lungs to de removed from the body. There are various proteins that are found in the plasma which have important functions. Fibrinogen, and protein is needed for the formation of blood clots, Serum albumin plays a large part of the osmotic pressure between plasma and blood cells and between plasma and tissues. Another protein, serum globulin contains antibiotic to fight diseases. Erythrocytes, red blood cells transport oxygen which is essential for the survival of cells in all parts of the body. When erythrocytes form in the red marrow of bones, an iron containing protein also forms. This protein called hemoglobin is the molecule that transports oxygen and carbon dioxide. When the corpuscles are formed the cell nucleus and organelles disintegrate. The mature erythrocyte is nothing more than a sac filled with hemoglobin. Because erythrocytes don't have a nucleus they can't repair themselves and so they live only about 130 days. Of the more than 30 trillion corpuscles circulating through the body at one time, about 0.0006% of these die each second. The remains are filtered out by the liver and the spleen, while the hemoglobin is sent back to the marrow, to be reused for more corpuscles. Leukocytes, or white blood cells, are the one who defend the body against diseases. They form in the red marrow of bones, lymph nodes, and the spleen. Leukocytes are much larger than erythrocytes, but they are less plentiful. In one drop of blood there are usually 5 million erythrocytes but only about 7,000 leukocytes. Usually the leukocytes function for years before dying and being replaced. Phagocytes, types of leukocytes engulf invading microorganisms. Others produce antibodies. Platelets are not whole cells but small portions that have broken off from the cytoplasm of larger cells formed in the marrow. Like the erythrocytes platelets lack a nucleus and live between 7 and 11 days. A platelet's main function is to form blood clots. This is so that excess blood loss can be prevented. When a blood vessel tears the platelets converge upon the tear, stick together and form a plug. They then release a protein which interacts with prothrombin, which is found in plasma. This interaction forms the enzyme thrombin which reacts with fribrinogen, a blood protein. Together thrombin and fibrinogen form long sticky threads called fibrin, which forms a net that traps erythrocytes. This structure then hardens into a clot or scab.

2. Discuss how each system works. Follow materials through a system, or show hoe signals, impulses, or substances are controlled, secreted or used.

The circulatory system distributes blood throughout the entire body. The blood caries oxygen and nutrients to all tissues and removes wastes as well. The heart is the organ that pumps blood through the body. It consists of cardiac muscles, nervous tissue, and connective tissues. Typically the heart beats 72 times and pumps about 5.5L of blood per minute. The heart lies in the thoracic cavity, between the lungs and the sternum. A though membrane called the pericardium, surrounds the heart and reduces friction as the heart beats by secreting a fluid. The septum divides the heart length wise into two halves. The riteside pumps blood to the lungs the left side pumps blood to the other parts of the body. Each side is then divided into an upper and lower chamber. The lower chambers are known as ventricles and the upper chambers are called atria, with one known as an atrium. In each side of the heart the blood always flows from the atrium to the ventricle. An atrioventicular valve in the left side prevents blood from flowing backwards and is called the bicuspid valve. Two semiluniar valves separate the ventricles from the large vessels that transport blood out of the heart. When blood returns to the heart it has a high amount of carbon dioxide. It first enters the right atrium and is then pumped through the tricuspid valve into the right ventricle. The muscle of the right ventricle then force the blood through the semiluniar valve into the vessels that lead to the heart. Carbon dioxide is exchanged in the lungs for oxygen and the blood is then pumped back to the heart. It enters the left atrium and is pumped through the bicuspid valve into the left ventricle. From here the blood is moved though the semiluniar valve into a vessel which transports the oxygenated blood throughout the body. Because the heart is made up of cardiac muscles the muscle cells contract in waves. This occurs when one cell is stimulated and it stimulates neighboring cells. This starts a chain reaction in which all the cells contract in a synchronous rhythm. This causes the heart to beat in a smooth motion. The stimulus begins in the sinoatrial node, which is located in the nerve and muscle tissues of the right atrium. The sinoatrial node is often called the pace maker because it regulates the contraction of the entire heart. The pace maker generates an electrical charge that stimulates the atria to contract. A tenth of a second later the impulse reaches the atrioventricular node, located in the septum between the atria. About a millisecond later the atrioventricular node sends the impulse to the ventricles. This electrical charge causes the ventricles to contract, which completes the full beating of the heart. The beat has two phases, the systole and the diastole. During the systole the ventricles contract and force blood into the antries. In the diastole phase the ventricles relax and the blood flows in from the atria. Every time the heart beats blood is moved through the blood vessels. The large muscular vessels that carry blood away from the heart are called arteries. The thick walls have three layers: an inner endothelium, a middle layer of smooth muscle, and an outer layer of connective tissue. This structure gives arteries a combination of strength and elasticity. When the left ventricle contracts, it forces blood into the bodies largest artery, the aorta. From the aorta the blood travels through a network of smaller arteries, which in turn divides and forms even smaller vessels called arterioles. After the arterioles branch into tiny blood vessels called capillaries, which are only one cell thick. Diffusion of gasses and nutrients takes place across the thin walls of the capillaries. In this way wastes are removed and nutrients are put into the cells. Deoxygenated blood flows through the capillaries and then they merge into larger vessels called venues. Several venues unite to form a vein, a large blood vessel that carries blood to the heart. The inferior vena cava transports blood from the lower part of the body. From the upper part of the body the venues merge to form the superior vena cava. The walls of the veins are also made up of three layers, but they are thinner and less muscular than those of the artery. The pressure within the veins is considerably less because of the distance the blood has to be pumped. Valve within the veins prevent blood from flowing backward. The lymphatic system is a part of the bodes circulatory system. It is a series of one way vessels that carry intercellular fluid from the tissue to the bloodstream. Some of the blood fluid passes through the capillary walls along with oxygen and nutrients but some fluid remains in the intercellular spaces. A buildup of this fluid would cause swelling of the tissues, and so it must be removed. The fluid collects at open ended vessels of the lymphatic system. Once the fluid enters the lymph vessels it becomes lymph. Lymph capillaries move the lymph through the lymph vessels and on to two large ducts, the thoracic duct and the right lymphatic duct. These two ducts empty into large veins found in the upper chest. The lymphatic system also plays a role in immunity by caching foreign particles as they pass by the lymph nodes. The nodes also produce lymphocytes which destroy pathogens. Another part of the circulatory system is that of a pulmonary subsystem. Pulmonary circulation is the movement of blood from the heart to the lungs and back. The right ventricle pumps blood into the pulmonary artery and then this blood goes to the lungs. This is the only artery that carries deoxygenated blood. When the pulmonary artery reaches the lungs it splits into two smaller arteries, one to each lung. These further branch into arterioles and then into capillaries. Blood in the capillaries absorb oxygen and release carbon dioxide. The oxygenated blood then flows through the venules, which merge into pulmonary veins that lead to the left atrium of the heart. Pulmonary veins are the only veins that carry oxygenated blood. Systemic circulation transports blood to all parts of the body except what the pulmonary circulation covers. Blood flows into the aorta from the left ventricle and enters systemic circulation. This circulation is further divided into subsystems: coronary circulation, renal circulation, and hepatic portal circulation. Coronary circulation is the subsystem that transports blood to the heart itself. Two coronary arteries branch off from the aorta and transports blood to the arterioles that penetrate the heart tissue. This blood then returns to the right atrium through a large vein known as the coronary sinus. If an artery becomes clogged and heart cells don't receive oxygen then they will die and a heart attack will result. Renal circulation delivers blood to the kidneys and back to the heart. Two renal arteries branch off from the aorta and one goes to each kidney. The kidneys filter the waste from the blood and then it goes back through the renal veins. The renal veins then join the inferior vena cava. A third subsystem is the hepatic portal circulation, which moves blood through the digestive tract and the liver. This subsystem involves two vessels. One of then is the hepathic artery, which is a branch of the aorta and delivers oxygenated blood. The other vessel is the hepatic portal vein, which brings blood with nutrients from the digestive tract to the liver. The hepatic portal vein branches into capillaries that distribute nutrients to the liver tissue. Blood from both the hepatic artery and the hepatic portal vein will eventually mix and leave through the hepatic vein, which joins the inferior vena cava.

3. Discuss diseases and dysfunctions related to each system.

The heart is a muscular pump. When its own tissue or blood vessels become diseased, serious and sometimes fatal harm can follow.

Disease of the coronary arteries that supply oxygen and nutrients to the heart is the most common heart ailment. Coronary artery disease accounts for more than a third of all deaths among males in the United States between the ages of 35 and 55. It also strikes many women past the age of 50. Hypertension (high blood pressure), overweight, cigarette smoking, diabetes mellitus, excess cholesterol, triglycerides and other fats in the blood, and probably lack of regular exercise contribute to the chance of getting coronary artery disease.

Coronary artery disease is characterized by an atheroma, a fatty deposit of cholesterol beneath the inner lining of the artery. The atheroma obstructs the passage of blood, thereby reducing the flow of nourishing blood to the heart muscle. It also sets up conditions for a blood clot in the coronary artery. Atheroma formation seems to run in families. Eating foods rich in saturated animal fat and cholesterol is also thought to contribute to atheroma formation.

Many persons with coronary artery disease do not experience symptoms. If the obstruction is bad enough, however, it may cause angina pectoris, myocardial infarction, or heart enlargement and failure.

Angina pectoris is a chest pain that feels like something is squeezing or pressing the chest during periods of physical exertion. It takes place when the heart's oxygen needs cannot be met because of a blocked coronary artery. Rest will relieve the pain. Some persons have angina pectoris for years and still live active lives.

Myocardial infarction is commonly called heart attack. Tissue death that results from a lack of blood is called infarction. When the coronary artery becomes so obstructed that the myocardium, or heart muscle, does not receive oxygen, it dies.

Once, it was believed that a blood clot occluded the coronary artery and caused the infarction. This is why a heart attack is sometimes called a coronary occlusion. However, it now appears that most clots form in the artery after the infarction.

The first few hours after a heart attack are the most critical because abnormal heart rhythms may develop. Ventricular fibrillation is the most dangerous. The ventricles of the heart contract so fast that the pumping action is balked. Death follows in three or four minutes. Heart attack patients are usually treated in the coronary care unit of a hospital for a few days to enable electronic monitoring of the heart rate and rhythm.

Heart failure can occur when repeated heart attacks put too much strain on the remaining healthy heart muscle. As attacks destroy more and more heart muscle, the remaining muscle hypertrophies, or enlarges, to maintain effective pumping. Pressure builds up in a weakened heart, however, and causes fluid backup in the lungs. As a result, the heart output cannot keep pace with the body's oxygen demands.

A node of special cells in the heart controls its rhythm by regularly producing energizing electrical signals. Sometimes, abnormal signals cause extra heart beats, or tachycardia.

At other times, especially in older persons, the signals might not be conducted too well through the heart, thus slowing it. When a person's heart rate drops below 40 beats a minute, he usually feels faint and cannot function well. In that case, he often can be fitted with an artificially powered heart pacemaker.

A doctor carefully questions and examines anyone suspected of heart trouble for evidence of pain, fatigue, abnormal heartbeat, and so on. He listens to the heart and lungs with a stethoscope. Sometimes, a heart murmur, a rushing noise heard through the stethoscope, provides a clue to a heart problem. A faint murmur can be normal, but a loud one usually indicates a diseased heart valve or other trouble. A chest X ray is usually taken to get a picture of the heart and lungs. An electrocardiogram reveals the electrical activity of a patient's heart.

A doctor can also rely on cardiac catheterization and angiography to diagnose heart disease. Cardiac catheterization involves slipping a catheter, a long tube, through veins into the heart to learn such things as how much blood the heart is pumping, whether its valves are damaged, and whether it is contracting as it should. Angiography involves injecting dye through a catheter into the heart so that subsequent X rays will reveal the internal anatomy of the heart and the blood flow through it.

Rheumatic heart disease has both an acute form and a chronic form. The acute form, rheumatic fever, inflames joints and heart muscle. The joints always recover, but if the condition becomes chronic the heart valves may eventually become scarred. Rheumatic fever most often affects the mitral, or bicuspid, valve of the heart and produces a blockage called mitral stenosis.

Rheumatic fever is a health problem in many of the world's developing nations. It is caused by an unusual body response to an infectious sore throat sparked by the bacterium beta hemolytic streptococcus. Uniquely, the bacterial cell wall and the human heart muscle have a protein in common. A person with a "strep" throat develops antibodies against the bacterial protein. However, the antibodies may also attack that person's own heart muscle, damaging it over the years. Penicillin and other antibiotics treat strep throat and can prevent heart damage. In severe cases after many years, however, surgery might be needed to repair or even replace a damaged heart valve.

Hypertension, or high blood pressure, is a fairly common disorder. Ordinarily, the heart creates sufficient pressure to send blood throughout the body. However, sometimes resistance to blood flow from the arteries is high and the blood pressure rises above normal. Because the heart must then work harder to maintain the higher pressure, it enlarges.

Blood pressure is maintained by means of a complex interaction between the heart, the nervous system, and a kidney hormone called renin. Some persons with hypertension have too much renin in their blood. High blood pressure increases the wear and tear on blood vessels. It also can cause heart failure, strokes, and kidney disorders. When discovered soon enough, it can be treated with drugs.

Sometimes the heart does not develop properly and a child can be born with a serious congenital heart disease. Heart valves might be too narrow or missing altogether, or the septum, a wall separating the heart chambers, might be incomplete. As a result, a hole exists between the heart chambers. Such congenital heart diseases can be discovered by means of cardiac catheterization and angiography and often can be corrected by a heart surgeon.

Some substances are dangerous to the heart. For example, diphtheria bacteria produce a toxin that damages the heart. Excessive alcohol drinking weakens and enlarges the heart. Persons with heart murmurs caused by faulty valves or congenital heart disease are susceptible to endocarditis, a bacterial infection of the inner lining of the heart. Also, certain viruses can cause myocarditis, inflammation of the heart muscle, and pericarditis, inflammation of the outer lining of the heart.

Atherosclerosis, the thickening and hardening of arterial walls, may occur in many arteries. Cholesterol and other fats that form in the process obstruct the affected arteries and, at times, produce a thrombus, or clot, in them. Sometimes, these clots break away, especially from the heart, and embolize, or travel to some other part of the circulatory system. There, they can block a blood vessel and keep oxygen away from a vital body part. Embolism in the brain, for example, can cause a stroke.

Aneurysm occurs when the walls of a large artery, especially the aorta, become weak and balloon out. Atherosclerosis can cause an aneurysm. So can syphilis. The venereal disease can also make the aortic valve leak.

Varicose veins, bulging veins in the leg, develop when the walls of the veins weaken. The condition may be inherited or may stem from phlebitis, an inflammation of the veins. Phlebitis may trigger clots in the veins, which sometimes break away, travel to the lungs, and form a pulmonary embolus. Drugs used to prolong clotting time often correct clotting disorder.