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Circulatory System Chapter 42 What you need to know! • The circulatory vessels, heart chambers, and route of mammalian circulation. • How red blood cells demonstrate the relationship of structure to function. • The pathway a molecule of oxygen takes from the air until it is picked up by the hemoglobin of a red blood cell. Cardiovascular System • System combining both the circulatory system and the respiratory system • Organs of exchange body cells (lungs, gills) Circulatory System Components: 1. Heart 2. Blood 3. Vessels Variation of Circulatory Systems • Open circulatory system (CS) in arthropods and mollusks: • Heart, and some main vessels filled with hemolymph (not blood) bath organs • Closed CS in vertebrates: • Blood remains in heart and vessels at all times Types of Blood Vessels 1. Arteries 2. Capillaries 3. Veins • Pathway (in closed CS): Heart arteries arterioles arterial capillaries venous capillaries venules veins back to heart Arteries • Always carry blood away from the heart • High pressure • Thick walls • Branch into smaller arterioles in organs • Once deep in the tissue they become… Capillaries • Microscopic blood vessels in the tissue • Deliver blood to every cell • Thin walls facilitate diffusion and osmosis • Exchange of gas, nutrients, and waste • Converge into… Veins • Always carry blood back to the heart • Venules are small veins (much like arterioles are small arteries) • Venules converge into larger veins • Low pressure • Thin walls • Valves prevent blood from flowing back into the tissue • Supported by surrounding smooth muscles • Superficial The Heart • • • • • • • • Hollow, muscular organ Pumps blood Chambers: Atria: entrance chambers Ventricles: main chambers Cardiac muscle surrounds the chambers Muscle contracts constricts chamber pumps blood out Valves prevent back flow Birds and Mammals • 4 chambers • 2 atria • 2 ventricles • Separated pulmonary circuit • High oxygen demands for endotherms and large brains Reptiles and Amphibians • 3 chambers • 2 atria, 1 ventricle • Oxygen rich and oxygen poor blood mix together in the ventricle Fish • 2 chambers • 1 atrium • 1 ventricle • Lower oxygen demand (exothermic) • Single pathway heart gills body back to heart • Muscle movement helps pump blood • Gills and arteries use counter-current exchange for maximum diffusion of O2 and CO2 Heart Rhythm Cycles: • Systole: contractions of chambers (pumping) • Diastole: relaxation of chambers (filling) • Atrial systole and ventricular diastole are simultaneous • Atrial diastole and ventricular systole are simultaneous Regulation: muscle cells contractions are orchestrated by: 1. Sinoatrial node (pacemaker) and 2. Atrioventricular nodes (delayed) • They are situated in the cardiac muscle and give off electrical impulses • Independent from the brain (involuntary) • Hearts can continue to beat after brain-dead (vegetable) Blood • A tissue Contains: • Cells • Red blood cells (RBC) and • White blood cells (WBC) • Plasma, and • Cell fragments • Platelets Red Blood Cell (Erythrocytes) • • • • • • • • • Shaped like disks Produced by bone marrow in hollow bones Loose nuclei during maturing (in humans) Lifespan 120 days Aged cells (3-4 months) are reabsorbed by the spleen and liver Blood type antigens Contains hemoglobin (protein with iron) for gas transport and exchange O2: bound loosely by hemoglobin in the lung, and is released as blood travels through the body CO2: 70% reacts with H2O (carbonic acid), 30% reacts with empty hemoglobin RBC Blood Types • A, B, AB, O encoded on genome inherited from parents • Determined by a surface antigen on erythrocytes Rhesus Factors of antigen (D): • Presence of antigen D = Rh + • Absence of antigen D = Rh – • Blood work at the beginning of a pregnancy is important to help prevent Rh- mothers from producing antibodies against an Rh+ child White Blood Cells (leucocytes/lymphocytes) • White blood cells are the largest portion of your immune response • 9 different types of WBCs (i.e. macrophages, b cells, t cells, etc.) • Have nucleus (unlike RBCs) • 1% of the blood • They identify and attack foreign substances and microorganisms (i.e. viruses, bacteria, and transplanted organs) • Also found in the lymphatic system Plasma • Straw colored liquid Contains: • H2O – 90% • Salts (isotonic to cell cytoplasm) • Proteins • Antibodies (as a result of inheritance as well as previous infections and vaccinations) Platelets • Pinched off from bone marrow cells • They release sticky networks of protein fibers (fibrin) when stimulated by air • Stops blood flow Lymphatic System • Plasma and protein can leak into tissue from the capillary beds • The lymphatic system returns this fluid (lymph) to the vena cava • Before returning the fluid it is filtered through lymph nodes (WBC filters) to remove viruses and bacteria Consists of: • Tonsils, thymus gland, spleen, and lymphatic vessels