BIOL 112 1st Edition Lec-ture 17 Outline of Last Lecture I. Significance of LiverII. Absorption of Water and SaltsIII. Circulatory SystemsIV. Components of Circulation SystemOutline of Current LectureV. Blood Vessels as TubesVI. Lymphatic SystemVII. Human Circulation MapVIII. Pumping Function of HeartIX. Fetal CirculationCurrent LectureI. Blood Vessels as Tubes•Artery: Multilayered tube (lu-men) - endothelium, smoothmuscles, connective tissue,epithelium, thicker and muchmore muscle than a vein,carry blood away from heart•Vein: Multilayered tube (lumen) - endothelium, smooth muscles, con-nective tissue, epithelium•Distinguish arteries and veinsThese 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 car-ries 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/exo-cytosis through endothelial cells•Functional Problem•Closed circulatory system under constant pressure throughout entire circuit•Consistent hydrostatic pressure means constant osmotic loss ofwater 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 osmoticflow recovery. But remaining 15% must be recovered by sepa-rate 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 (nor-mally no blood cells in this)•In small intestine, lymph vessel in each villus: lacteal. Involved in ab-sorption/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 up-per torso of body, major immune surveillance posts, remove bacteria,fungi, debris•Lymph vessels collect and eventually return lymph to blood circula-tion 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 scro-tum.•Cancer Metastasis: spread of cancer cells throughout body. lymph nodes do not filter out cancer cells because they are not recog-nized 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 sys-temic circuits, each driven by a separate pair of heart chambers•Double circulation essential to support high metabolism in animalsIV. 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 con-tract 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 calledpacemakers•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 signalfrom SA Node and passes it on, though Bundle of His, to both ven-tricles, both ventricles contract and pump blood out through arter-ies•Coordination of Heartheat•Nature of system serves to coordinate heart muscle contrac-tions 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 in-crease 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 regu-late 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 mecha-nisms:•Foramen Ovale: hole between the