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Circulatory and Respiratory Systems Biology Vertebrate Circulatory System • Closed system with a chambered heart that pumps blood through arteries that lead away from the heart to capillaries. • Capillaries—small vessels in tissues where exchange of materials take place • Blood is carried back to heart through veins Human Heart • • • • Located beneath the sternum About the size of your fist Composed mostly of cardiac muscle tissue 2 atria have thin walls and function as collection chambers for returning blood • 2 ventricles have thick, powerful walls that pump blood to the organs Blood Vessels • Arteries—carry blood away from the heart to the tissues – Branch into smaller arterioles, which supply blood to tissues via capillaries – Thick-walled, muscular (smooth muscle), and elastic, transporting blood at high pressure – Blood is oxygenated, except the pulmonary artery that carries deoxygenated blood from tissues to lungs through the right atrium and ventricle • Veins—carry blood to the heart from the capillaries – Capillaries branch into larger venules, which supply blood to veins and back to the heart – Thin-walled, little smooth muscle, transporting blood at low pressure, and contain many valves to prevent backflow – Veins have no pulse and carry deoxygenated blood, except the pulmonary vein which carries oxygenated blood from the lungs – Skeletal muscle contraction aids in systemic circulation • Capillaries—thinwalled vessels (simple squamous) • Permit exchange of materials between blood and body cells • Capillaries • Fluid containing water with nutrients and hormones seep from capillaries into tissues, driven by pressure • Cells and proteins are retained in the capillaries and draw water back into the capillaries by osmosis • Excess fluid in tissue can enter lymphatic system to be filtered and cycled back to the circulatory system Blood Components Erythrocytes: Red Blood Cells • Primary function to carry oxygen • Produced in red bone marrow of bones • Mature cells lack nuclei and circulate ~4mos. • Mature cells lack mitochondria—produce ATP without oxygen through glycolysis • Contain hemoglobin-pigment that binds oxygen Erythrocytes: Red Blood Cells • Red blood cells (rbc) manufacture 2 antigens, antigen A (Blood Type A) and antigen B (Blood Type B) – No antigens create the Blood Type O • Plasma carries antibodies for the antigens that are not present on the rbcs Leukocytes: White Blood Cells • Involved in immune functions in the body – Phagocytes—engulf bacteria – Lymphocytes (B and T cells)—immune response • B cells produce antibodies • Helper T cells kill infected cells Leukocytes: White Blood Cells • Platelets—cell fragments produced in marrow – Involved in blood clotting mechanism – Activation of a protein in the blood, fibrin, that forms a net across the wound, trapping more cells and blocking the flow of blood Two separate circulatory loops –Pulmonary circulation • Pumps oxygen-poor blood through pulmonary arteries to the lungs • Pick up O2/Unload CO2 • Oxygenated blood returns to left side of heart through pulmonary veins –Systemic circulation • Pumps oxygen-rich blood through arteries to the tissues of the body • Delivers O2/Picks up CO2 • Returns deoxygenated blood to right side of heart through veins Four valves function to prevent backflow of blood –Atrioventricular valves • Prevent backflow when ventricles contract –Semilunar valves • Prevent backflow when ventricles relax Control of Heart Rhythm • Sinoatrial (SA) node—cells are selfexcitable—generate electrical impulses • Cardiac muscle cells are electrically coupled by intercalated discs b/w cells Control of Heart Rhythm • Atrioventricular (AV) node—receives signal from atria, delays 0.1 sec, and then sends signal throughout walls of ventricle Cardiovascular Disease • Heart attack—death of cardiac muscle tissue resulting from artery blockage of one or more coronary arteries which supply oxygen to the heart • Stroke—death of nervous tissue in the brain resulting from artery blockage in the head Ventilating Lungs: Breathing Automatic Control of Breathing • Breathing control center in brain = medulla oblongata and pons • Monitors CO2 levels in blood by changes in pH – CO2 + H2O Carbonic acid – pH = depth and rate of breathing • altitude = O2 levels • Sensors in aorta and carotid arteries detect and signal control center to breathing rate Loading and Unloading of Respiratory Gases Oxygen Transport • Oxygen carried by respiratory pigments – Vertebrates utilize hemoglobin—four heme groups surrounding an Fe atom • Can carry four oxygen atoms Carbon Dioxide Transport • Hemoglobin transports CO2 and assists with buffering the blood—prevents dramatic changes in pH • 7% CO2 released by cells transported as dissolved CO2 in plasma • 23% binds to amino group of hemoglobin in red blood cells • 70% transported in form of bicarbonate ions Emphysema • Alveoli lose their elasticity • Makes it difficult to release air during exhalation • Person must use more and more energy just to breathe • Person suffers from constant fatigue and breathlessness Lung Cancer • Abnormal cell growth • Affected lung is usually removed • Fewer than 10% of lung cancer victims live more than 5 years