B6A7CirculateS10

B6A7CirculateS10 - Circulatory Systems Circulatory Systems...

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Unformatted text preview: Circulatory Systems Circulatory Systems Circulatory Systems Functions: • Transportation – Water & electrolytes (salts) – Dissolved gases— O2 & CO2 – Nutrients – Wastes – Chemical messengers (hormones) – Defense (immune) systems – Repair (clotting) factors • Thermoregulation • Hydraulics Circulatory Systems • Ciliated Body Cavity • Open Circulatory System • Closed Circulatory System Cardiovascular System Lymphatic System Size & System Development • Diffusion is sufficient for small organisms w/ low volumes & metabolic demands (e.g. protozoans and micrometazoans). Hemocoel Ciliated Body Cavity Heyer Cnidarians & Platyhelmintheans • gastrovascular system – ciliated digestive cavity w/ branching extensions. Circulatory Systems Echinoderms • water vascular system – ciliated coelom w/ extensions (dermal branchae & tube feet) for respiration. – Important hydraulic functions Vascular System Components • Four components are –1) circulatory fluids –2) vessels –3) pump –4) valves • Vasculature (vessels) may form open or closed circulatory system Open Circulatory Systems Open Circulatory Systems • In arthropods & most molluscs. • 4-part system - what are those parts? • circulatory fluids mix w/ interstial fluids of body cavity. • Hence, “blood” is called hemolymph. • Dorsal heart pumps hemolymph out vessels into body cavity (= hemocoel) • Hemocoel partially compartmentalized into sinuses • Hemolymph returns to heart via ostia or veins. Open Circulatory Systems Dorsal Vessel as Pump • Whole dorsal vessel may act as a tubular heart – Insects • Specific region specialized into a heart – Crustaceans & Molluscs – Hemolymph pulled from hemocoel by veins to gills to heart to arteries to hemocoel Heyer Limitations of Open Systems • Difficult to regulate different perfusion of different tissues. • Great for small body plans; not so great for big bodies with variable metabolic activities. • How can it be enhanced for large bodies? Circulatory Systems Closed Circulatory Systems • Complete circuit between heart, arteries & veins with capillaries. • Better circulation + better regional control fi higher activity levels. • Problem: if circulatory fluid is confined to vessels, how does exchange occur??? Closed Circulatory Systems in Vertebrates Pre-pump Main pump Closed Circulatory Systems • Cephalopod molluscs have 3 hearts — one to each gill and one for the body. • Annelid worms use dorsal vessel plus anterior lateral branches as heart. Closed Circulatory Systems in Vertebrates • Heart is from ventral vessel, not dorsal vessel. • Fish – 2-chambered heart – Single circuit : blood flows from heart to gills, and then to systemic vessels – Blood pressure drops when flowing through the gill capillary beds. – Muscle contraction during swimming accelerates blood flow in the vessels. [Efferent] [Afferent] • Cardiovascular system Closed Circulatory Systems in Vertebrates Closed Circulatory Systems in Vertebrates • Amphibians & (Most) Reptiles • Amphibians & (Most) Reptiles – 3-chambered heart • 2 atria/1 ventricle – Double circuit : • 1a. (amphibians) Pulmocutaneous circuit: blood flows from heart to lungs & skin • 1b. (reptiles) Pulmonary circuit: blood flows from heart to lungs only • 2. Systemic circuit: repressurized blood flows from heart to systemic vessels – ~10% mixing of deoxygenated + oxygenated blood in single ventricle Heyer – 3-chambered heart • 2 atria/1 ventricle – Double circuit : • Pulmocutaneous circuit: blood flows from heart to lungs & skin • Cutaneous exchange may include skin, throat, and/or gills (in larvae & neotenes ) • Pulmonary flow may be diverted to cutaneous while underwater Circulatory Systems Closed Circulatory Systems in Vertebrates Closed Circulatory Systems in Vertebrates • Crocodilians, Birds & Mammals • Crocodilians – 4-chambered heart – 4-chambered heart • 2 atria/2 ventricles • 2 atria/2 ventricles – Double circuit : – Double circuit : • 1. Pulmonary circuit: blood flows from heart to lungs only • 2. Systemic circuit: repressurized blood flows from heart to systemic vessels – No mixing of deoxygenated + oxygenated blood – Pulmonary & systemic circuits are pressurized differently – >10x more efficient systemic oxygenation • 1. Pulmonary circuit: blood flows from heart to lungs only • 2. Systemic circuit: repressurized blood flows from heart to systemic vessels – Shunt to divert pulmonary to systemic flow when underwater Review of Designs Mammalian Cardiovascular System • Two circuits, each with its own 2-chamber pump – Different pressure – Same flow rate Mammalian Cardiovascular System Mammalian Cardiovascular System • Pulmonary circuit: • Systemic circuit: • Right pump ÆlungsÆleft pump • Left pump Æbody Æright pump q Deoxygenated systemic blood fills right A&V q Right A&V contract pushing deoxygenated blood through pulmonary artery to lungs q q Release CO 2 Take up O 2 q Oxygenated blood from lungs flows through pulmonary veins to left atrium Heyer q Oxygenated pulmonary blood fills left A&V q Left A&V contract pushing oxygenated blood through aorta to branching major arteries to all other body organs q q Release O 2 Take up CO 2 q Deoxygenated blood from body tissues flows through branches of veins converging on vena cava to right atrium Circulatory Systems Human Heart Anatomy The Pump • For any pump to function, it needs two components: 1. Constriction (stroke) chamber Øchamber volume fi ↑pressure fi move fluid • Diagrams show heart from front – Viewer’s “right” is heart’s “left” • Enclosed in fluidfilled sac behind sternum 2. Valves fi direct fluid flow direction Human heart in chest cavity The Vessels Cardiac Contractions • • • • • 1. Sinus node (pacemaker) fires 2. Signal spreads across atria 3. Cardiac muscle in atria contract 4. Signal reaches AV node; travels down Bundle of HIS to apex of heart 5. Signal spreads across venticles 6. Cardiac muscle in venticles contract Arteries – carry blood away from the heart Arterioles – smaller branches of arteries Capillaries – thin, microscopic, with porous walls Venules – smaller branches that converge into veins Veins – carry blood back to heart Vessel Structure & Function • Arteries: blood away from heart Artery Poisseuille’s Law Vein – Thick-walled and elastic to withstand higher pressure • Capillaries: thin-walled and highly branched – Only vessels exchanging with tissue fluids! – Walls only 1 cell thick to maximize diffusion rates – Not permeable to blood cells & proteins; permeable to water and other solutes Heyer Valve 100 µm Basal lamina Endothelium Connective tissue • Flow rate = f = (Dyp)(pr4)/(8Lh) Endothelium Smooth muscle Smooth muscle Capillary Connective tissue Artery Vein Arteriole Red blood cell Venule 15 µm – Thin, compliant walls – Internal valves prevent backflow The Hagen-Poiseuille Equation: SEM where ß Dyp= pressure difference ß r = radius ß h = fluid viscosity ß L = length of tube • NOTE: Capillary LM • – Smooth muscle in arteriole walls regulate selective blood flow Veins: blood toward heart Fig. 42.10 Df proportional with Dr4 ! Circulatory Systems Circulatory Changes During Exercise Selective flow regulated by dilating & constricting specific arterioles Capillary beds — the sites for exchange • In addition to regulation by vasodilation /vasoconstriction of arterioles, localized perfusion regulated by pre-capillary sphincters • Only 5 –10% of capillaries open at a given time Capillary beds — the sites for exchange Capillary beds — the sites for exchange • In addition to regulation by vasodilation /vasoconstriction of arterioles, localized perfusion regulated by pre-capillary sphincters • Only 5 –10% of capillaries open at a given time Capillary beds — the sites for exchange Body tissue Capillary filtration Capillary filtration • Blood pressure (P B) pushes fluid out • INTERSTITIAL FLUID Net fluid movement out Net fluid movement in • Osmotic pressure (POsm ) pulls fluid in • At arteriole end of capillary: (P B) > (P Osm ) • At venule end of capillary: ( POsm ) > (PB) Direction of blood flow Blood pressure Pressure • Walls only 1 cell thick to maximize diffusion rates Not permeable to blood cells & proteins Permeable to water and other solutes Capillary Inward flow Outward flow Osmotic pressure Arterial end of capillary Heyer Venous end Circulatory Systems Capillary exchange • Fluids not returned to capillaries goes to lymphatics Lymph node Lymphatic System • Recaptures lost fluids & proteins – 85-90% fluid returned to blood circulation – 10-15% taken up by lymphatic capillaries • Interstitial fluids filtered through lymphoid tissues and monitored by immune system • Fluids return to CV system in vena cava Fluid Flow in Veins — both Cardiovascular & Lymphatic Systems Blood: Liquid Tissue Cells Suspended in Plasma • Fluids pumped by “skeletal muscle pumps” • Valves prevent backflow The composition of blood Blood Structure and Function Clotting “Formed Elements” — cells and cell-derivatives Since erythrocytes and thrombocytes lose their nuclei, they are no longer truly cells. • Erythrocytes (red blood cells) – Carry oxygen • Leukocytes (white blood cells) – Defense/clean up • Thrombocytes (platelets) – Blood clotting Clotting Factors Prothrombin Thrombin Fibrinogen Fibrin • Leukemia victims lack platelets • Hemophiliacs lack clotting factors. Plasma • 90% H2O • 7–9% protein Human blood smear Heyer Plateletes ...
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This note was uploaded on 01/11/2012 for the course BIO 6A taught by Professor Bruceheyer during the Winter '12 term at DeAnza College.

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