BIOL 112 1st Edition Lecture 17 Outline of Last Lecture I Significance of Liver II Absorption of Water and Salts III Circulatory Systems IV Components of Circulation System Outline of Current Lecture V Blood Vessels as Tubes VI Lymphatic System VII Human Circulation Map VIII Pumping Function of Heart IX Fetal Circulation Current Lecture I Blood Vessels as Tubes Artery Multilayered tube lumen endothelium smooth muscles connective tissue epithelium thicker and much more muscle than a vein carry blood away from heart Vein Multilayered tube lumen endothelium smooth muscles connective tissue epithelium Distinguish arteries and veins These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Structural Artery thicker walls more muscle than vein veins have valves arteries do not Functional Artery carries blood away from heart vein always carries blood towards heart Capillaries Between arteries and veins in circulation cycle Only one cell layer thick endothelium cells All exchanges occur through endothelial cells of capillaries Exchanges involve diffusion active transport and or endo exocytosis through endothelial cells Functional Problem Closed circulatory system under constant pressure throughout entire circuit Consistent hydrostatic pressure means constant osmotic loss of water from blood to tissue fluids about 3 liters day How does body deal with excess accumulated fluids About 85 of fluid lost from capillaries reenters circulation by osmotic flow recovery But remaining 15 must be recovered by separate circulatory component the lymphatic system II Lymphatic System Lymph Vessels Like veins have valves Lymph Capillaries Like blood capillaries but have closed ended tubes collect excess fluids from intercellular spaces of tissues lymph normally no blood cells in this In small intestine lymph vessel in each villus lacteal Involved in absorption processing of lipids from digestion Also colonies of lymphatic immune cells in walls of intestines Peyer s Patches Immune surveillance of digestive organs Lymph Nodes filter lymph as it professes through vessels towards upper torso of body major immune surveillance posts remove bacteria fungi debris Lymph vessels collect and eventually return lymph to blood circulation at major connection site thoracic duct Failure of Lymphatic Return Elephantiasis caused by tiny parasitic roundworms lodging in lymph nodes and plugging up lymph system no lymph flow leads to accumulation of lymph fluids in area normally drained by a part of lymph system leads to gross swelling of leg or arm or scrotum Cancer Metastasis spread of cancer cells throughout body lymph nodes do not filter out cancer cells because they are not recognized as being foreign even through they are cancer cells use lymph system as vehicle for spreading throughout the body III Human Circulation Map Pulmonary Circuit Right atrium Right Ventricle pulmonary artery lungs pulmonary vein Systemic Circuit Left atrium left ventricle aorta system vena cava Heart is a double pump system with separate pulmonary and systemic circuits each driven by a separate pair of heart chambers Double circulation essential to support high metabolism in animals IV Pumping Function of Heart Made up of cardiac muscle Contractions are intrinsic meaning they will contract beat without outside stimulation and rhythmic meaning periodic spontaneous contractions Even isolated cardiac cells will twitch rhythmically A group of cells together become electrically connected so they contract together They connect by intercalated discs Heart doesn t need connections to nervous system to beat effectively Pacemakers In an intact heart coordination of contractions leading to efficient pumping is controlled by centers of specialized muscle cells called pacemakers Pacemakers impose contraction signals on rest of heart Primary Pacemaker Sino atrial Node SA Node located in right atrium specialized cells generate an electrical contraction signal propagated to rest of heart both atria contract and pump blood from atria into ventricles and then a pause occurs Secondary Pacemaker Atrio ventricular Node AV Node located on boundary between atria and ventricles AV Node receives signal from SA Node and passes it on though Bundle of His to both ventricles both ventricles contract and pump blood out through arteries Coordination of Heartheat Nature of system serves to coordinate heart muscle contractions so that heart will function as an efficient pump Pathology fibrillation uncoordinated contractions in ventricles produce ripples over structure and not a coordinated pumping contraction Can be quickly fatal if not stopped Note that no outside connections are needed to get heart to beat pump Control of Heartbeat nervous system regulates rate and force of heart contractions Most nervous system connections are to SA Node Nerves stimulate or inhibit pacemaker activity and therefore increase or decrease heart beat rate For example one nerve connected to SA node the Vagus Nerve causes a significant decrease in heart beat rate when it is stimulated Other nerves will speed up node Pacemakers also sensitive to various hormones and drugs in blood epinephrine caffeine nicotine etc Routing of Blood Flow Microcirculation Nervous system can also control details of where blood is routed throughout body Microcirculation is achieved by a series of sphincter circular muscles at the ends of various arteries connecting to capillary beds Sphincters can be contracted or relaxed and thus regulate how much blood flows through which capillaries Examples Blush face neck areas thermoregulation second wind phenomenon spleen extra reserve of about 1 2 cup of blood if needed V Fetal Circulation Applies only to placental mammals only Circulation in fetus is necessarily different from post birth baby or adult Lungs collapsed no gas exchange and little blood circulation through lungs Gas exchange through placenta this in systemic not pulmonary circulation system Blood flow rerouted to bypass pulmonary circulation by 2 mechanisms Foramen Ovale hole between the two atria blood from systemic circulation enters heart in right atrium but during systole most of this is moved into left atrium through foramen instead of right ventricle Foramen circumvents right ventricle and lungs Ductus Arteriosus Connection between pulmonary artery and aorta Blood pumped by right ventricle enters pulmonary artery