2. Functions of The Human Circulatory System The human circulatory system, or cardiovascular system, has the great job of transporting oxygen and nutrients to the organs and tissues of the body, and to carry away waste products.The human circulatory system, or cardiovascular system, has the great job of transporting oxygen and nutrients to the organs and tissues of the body, and to carry away waste products. It regulates the body’s temperature and increases blood flow to meet demands during exercise.It regulates the body’s temperature and increases blood flow to meet demands during exercise. This system also sends parts of the immune system (white blood cells and antibodies) to fight off foreign substances upon their invasion.This system also sends parts of the immune system (white blood cells and antibodies) to fight off foreign substances upon their invasion. Should injury or bleeding occur, it sends clotting cells and proteins to help stop bleeding and promote healing.Should injury or bleeding occur, it sends clotting cells and proteins to help stop bleeding and promote healing.

3. Follow me! Bluish, deoxygenated blood enters the heart at the right atrium, through the vena cava. It then drops down to the right ventricle through a valve that opens only in one direction. Entering the pulmonary artery, the blood next goes to the lungs, where it is “reimbursed” with oxygen, becoming bright red again. It goes back to the heart through the pulmonary veins to the left atrium. This voyage through the lungs is pulmonary circulation. Its function is to fill the blood with oxygen from the lungs. Next, it’s down to the left ventricle, the most powerful chamber of the heart. From here it enters the aorta, to the body’s arteries, then arterioles, to veinioles, to veins, and finally back to the vena cava. This journey throughout the body is called systemic circulation. Its mission is to bring oxygen to the organs and tissues of the body, and to carry away waste materials back to the lungs, where they are exhaled. When blood is being transmitted through the heart, that is coronary circulation. A single drop of blood goes a long way through the human body. In fact, if all the arteries, veins, and capillaries in an adult human’s body were placed end to end, the total length would stretch nearly two and a half times around the earth’s equator. This is over 100,000 km (60,000 miles). Blood on the right side of the heart is bluish and the oxygen has all been used up. Blood on the left side, however, is bright red and full of oxygen to take to the body.

4. BLOOD Blood is made up of red and white blood cells, and platelets, all carried in plasma:Blood is made up of red and white blood cells, and platelets, all carried in plasma: –Red blood cells: bear oxygen Hemoglobin: bears iron (inside the red b.c.’s)Hemoglobin: bears iron (inside the red b.c.’s) –White blood cells: fight disease (a part of the immune system) –Platelets: clot blood--this slows, stops bleeding –Plasma: yellowish, it consists of water, salts, proteins, vitamins, minerals, hormones, dissolved gases, and fats.

5. BLOOD PRESSURE Blood pressure is the pressure generated when the pumping action of the heart propels blood to the arteries. It’s measured using a sphygmomanometer, wrapped around the upper arm. This is displayed as a ratio--average is 120/80. Blood pressure is measured during systole and diastole. –Systole: active pumping phase of the heart. –Diastole: resting phase between heartbeats. Heartbeats are triggered by myocardium, the muscle forming the walls of the heart’s four chambers. This muscle rhythmically and continuously contracts to pump blood. The pumping phase of the heartbeat consists of two cycles: systole, the pumping of the heart; and diastole, the resting in between pumps.

6. DISEASES OF THE HEART Hypertension - High blood pressure: blood vessels narrow, making heart pump harder. - Eventually the heart will need more oxygen. This can lead to heart failure or brain stroke. Atherosclerosis - High concentrations of cholesterol lead to plaque, which deposits on the sides of arteries, reducing blood flow. - Blood clots can form where plaque roughens artery walls. - This causes damage to organs. * When a brain artery is blocked--stroke. * When a coronary artery is blocked--heart attack, and heart muscle is destroyed.