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CIRCULATORY SYSTEM Part 1 Grade 8 Semester 1 Year 2011-2012 Blood as the Transport Medium To supply oxygen and glucose, as well as other substances, large organisms have a specialised transport system. This system has 4 parts: A medium-blood A system of tubes-arteries and veins A pump-heart Sites of exchange-capillaries Blood Content Types of Blood Cells Cell Type Appearance Function Structure Red blood Cells (erythrocytes) Transport O2 from lungs Contain haemoglobin Have no nucleus Cells are smalls and flexible White Blood Cells (Phagocytes) Remove microorganisms that invade the body and might cause infection by engulfing them. Irregular shaped nucleus Enzymes in cytoplasm digest microorganisms once engulfed Sensitive cell surface membrane White Blood Cells (Lymphocytes) Produce antibodies-as defense against diseases Large nucleus contains may copies of genes for antibody production Platelets Involved in blood clotting Can release blood clotting enzyme Blood Clotting Collagen fibers Platelet plug Fibrin clot Platelet releases chemicals that make nearby platelets sticky Clotting factors from: Platelets Damaged cells Plasma (factors include calcium, vitamin K) Prothrombin Thrombin Fibrinogen Fibrin 5 µm Red blood cell Blood Plasma Our transport medium has watery liquid part that is called plasma. Plasma has transport function which carries dissolved food molecules, waste materials, and hormones. Plasma is also able to distribute heat around the various part of the body. The Heart It is a double pump It contracts (systole) and relaxes (diastole) It has 4 chambers Each chamber pumps the same volume of blood Heart rate/pulse: 72 beats/min Blood Vessels The blood flows away from the heart in vessels called arteries. The blood flows back towards the heart in vessels called veins. Joining the arteries and veins are the capillaries. Main artery: aorta Main veins: vena cava Transverse Section of Vessels Narrow central tube (lumen) Wide central tube (lumen) Artery: Blood is rich in oxygen (except in the pulmonary artery); High pressure. Vein: Blood is low in oxygen (except in the pulmonary vein); Low pressure; has pocket valve. Capillary: One cell thick; large surface area Capillaries Tissue cell Capillary Red blood cell 15 Net fluid movement out Net fluid movement in m At the arterial end of a capillary, blood pressure is greater than osmotic pressure, and fluid flows out of the capillary into the interstitial fluid. At the venule end of a capillary, blood pressure is less than osmotic pressure, and fluid flows from the interstitial fluid into the capillary. Direction of blood flow Blood pressure Osmotic pressure Pressure Capillary INTERSTITIAL FLUID Inward flow Outward flow Arterial end of capillary Venule end The mammalian cardiovascular system 7 Capillaries of head and forelimbs Anterior vena cava Pulmonary artery Aorta Pulmonary artery 9 6 Capillaries of right lung Capillaries of left lung 2 4 3 Pulmonary vein 5 1 Right atrium 3 11 Left atrium Pulmonary vein 10 Left ventricle Right ventricle Aorta Posterior vena cava 8 Capillaries of abdominal organs and hind limbs