Mid-Unit Summary

     The first concept we covered was the structures of the heart and its correlation to their functions. The heart is covered by the pericardium which secretes a fluid that keeps it lubricated and reduces friction. The heart is broken up into four chambers: the right atrium which is in charge of receiving oxygen deprived blood, the right ventricle which discharges blood, the left atrium which receives oxygen-rich blood and the left ventricle which takes oxygenated blood from the lungs. The valves of the heart prevent back flow and keep blood flowing in one direction.  The nodal system is built into the heart tissue with the SA node starting each heartbeat, and a delayed AV node that waits for blood to move into the ventricles. The cardiac cycle is divided into the systole and the diastole. The systole is in charge of contraction while the diastole is in charge of relaxation. Oxygen-rich blood flows from your aorta to the arteries to arterioles, and to the capillaries. Oxygen poor blood travels from the venules to veins to the vena cavas, to the heart and finally ot the pulmonary artery.
     The second concept we learned was the major features of the circulatory system. Its major components include the heart: a network of tubes that continuously circulates with arteries carrying blood away from the heart and veins bring blood back to the heart. This system is enclosed inside your body so if blood escapes outside of the system, internal bleeding will result. The normal measurement of blood pressure is 120/80.
     The third lesson was about the functions and dysfunctions of blood vessels. Veins carry blood back to the heart from tissues while arteries carry blood away from the heart to tissues and is made up of elastic and contractile muscle. Capillaries are tiny vessela that connect arteriole to venules. Unhealthy blood vessels result in atherosclerosis in which bessels become clogged with plaque resulting in no blood flow to the rest of the vessels. An Aneurysm is a weakened section of the blood vessel wall that is caused by atherosclerosis, high blood pressure, trauma/injury, and stimulant drugs.
    The fourth lesson we learned was the different components in our blood and how they affect our health. Blood functions to transport oxygen, carbon dioxide, and nutrients throughout our body. It regulates our body temperature, and protects against infections. The different blood types are A, B, AB, and O based on the presence of antigens. Red blood cells have no nucleus and carry oxygen. Once the are worn out, the are recycled in the spleen, liver, and red marrow. A defect in red blood cells in which the cell becomes sickle shaped is called Sickle Shape Anemia and results in reduced oxygen to tissues. There are 5 different types of white blood cells. Neutrophils are in charge of ingesting bacteria and are active phagocytes; basophils are involved in inflammation and allergic reactions; eosinophils fight parasitic worms; lymphocytes attack virisus and secrete antibodies; monocytes arrive at site of an infection and destroy more microbes; and finally plateles form a chain reaction that leads to blood clotting.
     In the atherosclerosis reading, it wrote about how our bodies naturally produce substances that fight and prevent blood clots from "materializing", but if plaque builds up in our arteries, this inhibits the release of those substances. The inake of LDL in our Western culture excess the necessary amount our bodies demand, which actually "promotes aterial disease."
     The fifth lesson we learned was how heart attacks and strokes are identified and treated. A heart attack is defined by a stopping of blood supply to the myocardium which results in damage/death to heart cells. A cardiac arrest may occur before a heart attack as the heart's electrical system malfunctions and the heart stops. When access supgars and plyunsaturated fats builds up in blood vessels, atherosclerosis may occur. There are two different types of cholesterol: LDL and HDL. LDL are bad for our arteries ad they stick to garbage. HDL is good and cleans up LDL like a garbage truck. To detect a heart attack in progress, eletrical tests such as an EKG, angiography, echocardiogram, or electrocardiogram is taken.
     Strokes are very dangerous because often times, symptoms are not seen and when they are, it is too late. During a stroke two million brain cells die each minute. There are drugs like tPA and TIA that can help treat strokes; however, they are only efficient if you are treated with them soon enough. The highest risk of a stroke is high blood pressure, so the most important way to avoid a stroke is to prevent it through healthy diets, frequent exercise, little alcohol consumption, and tracking blood pressure.