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