Blood Flow Lecture PDF

Blood flow Blood flow Learning goals Understand the basic architecture of the circulatory system Learn what determines flow Understand flow rate vs flow velocity Understand the structure of blood vessels and how blood pressure changes in different vessels Functional model of the Car...

Blood flow Blood flow Learning goals Understand the basic architecture of the circulatory system Learn what determines flow Understand flow rate vs flow velocity Understand the structure of blood vessels and how blood pressure changes in different vessels Functional model of the Cardiovascular System Elastic arteries Aorta Aortic valve Left ventricle Left heart Mitral valve Arteriole with Left atrium variable radius Pulmonary veins a Exchange of Lungs Capillaries material with cells Pulmonary artery Pulmonary valve Venules Right ventricle Right heart Tricuspid valve Right atrium Venae cavae Venous valves Expandable veins Figure 15-1 Flow is determined by pressure Hydrostatic pressure— pressure exerted by fluid on the walls of a container. Physics was here first!!!! Physiology Pressure falls with distance as energy is lost to friction Flow can be made by pressure gradients Higher P Lower P Flow Pressure gradient is about the difference “DP” Flow µ DP DP = Higher P – Lower P absolute youcan changethe s keepthe flow Flow is determined by the pressure gradient 100 mm Hg 75 mm Hg Flow Pressure gradient is about the difference “DP” Flow µ DP DP = 100 – 75 = 25 Flow is determined by the pressure gradient 40 mm Hg 15 mm Hg Flow Pressure gradient is about the difference “DP” Flow µ DP DP = 40 – 15 = 25 Same DP, same flow Flow Rate vs Flow Velocity Flow 100 mL Flow Rate = volume of fluid/time Flow Rate = 100 mL/1 sec 5L/min at rest flowrate volumeoffluid time vs Particlemovement distance flowvelocity time Flow Rate vs Flow Velocity Flow 10 mm Flow Velocity = distance/time Flow Velocity = 10 mm/1 sec Functional model of the Cardiovascular System 5L/min at rest Elastic arteries Aorta Aortic valve diverting flow Left ventricle Left heart Mitral valve Arteriole with Left atrium variable radius Pulmonary veins Exchange of Lungs Capillaries material with cells Pulmonary artery Pulmonary valve Venules Right ventricle Right heart Tricuspid valve Right atrium contraction Venae cavae narrowingthetub will increasethevelocity Expandable veins Constrict to increase tone and velocity Figure 15-1  Resistance & tube radius affect general “flow”-pinching/diversion model Resistance µ 1/radius4-so? Flow µ 1/R-so? Tube A Tube B Tube A Tube B R µ 1/14 R µ 1/24 Flow µ 1/1 Flow µ 1/(1/16) Rµ1 R µ 1/16 Flow µ 1 Flow µ 16 largertheradius smaller resistance smaller resistance greater flow largerthe resistance smaller flow greater Heraladius A B R = Resistance r = radius r=1 r=2 Velocity changes as a function of cross sectional area Flow rate = 34 cm3/sec X A = 1 cm2 Y A = 17 cm2 Velocity = flow rate cross sectional area (A) Point X 34 cm3/sec/1 cm2 = 34 cm/sec Point Y 34 cm3/2/17 MM cm2 = 2 cm/sec Capillaries actually have huge cross sectional area Flow rate = 5000 cm3/min ACap = 5000 cm2 Velocity = flow rate cross sectional area (A) Smaller the denominator higher the velocity AAorta = 200 cm2 VAorta = 5000 cm3/min 200 cm2 VAorta = 25 cm/min areais to the areaof 1 aorta VCap = 5000 cm3/min 5000 cm2 aitntiiitiar.es VCap = 1 cm/min Why do we want velocity to be low at the capillary bed? bed iswhereexchange happens wantit to beslow  4 4 Structure of blood vessels reflects function Snap-back Valves Valve Exchange Figure 15-2 Elasticity and recoil of arteries maintains blood flow Arterioles 1 Elasticity and recoil of arteries maintains blood flow snapback doesntrequireenergy to shoot 1 Ventricular contraction blood toward after contration 2 Semilunar valves open 1 2 4 3 3 Aorta and arteries expand, store energy in elastic walls 4 Elastic recoil sends blood forward. Blood flow Lecture B Blood flow Lecture B Learning goals Know Mean Arterial Pressure (MAP) and its determinants Understand how blood volume is controlled within the circulatory system Blood pressure decreases moving through system Clinical Definitions of blood pressure MAP Blood pressure = arterial pressure Dia=Dialating Several types of pressure to consider Pulse Pressure (range) = systolic pres. – diastolic pres. Mean Arterial Pressure = MAP=1/3 PP + diastolic pres. 2/3DP + 1/3SP=A reflection of pressure range and time spendlesstimein Pulse systole thandiastole Pressure Ramp-to Peak youspend most time Sphygmogram=pressure in diastole over time Measuring blood pressure: Sphyg”momanometry” (a) Cuff pressure Brachial Artery > 120 mm Hg Inflatable Silent cuff Pressure gauge Stethoscope Figure 15-7 Measuring blood pressure: Sphygmomanometry (a) Cuff pressure > 120 mm Hg Inflatable Silent cuff Pressure gauge (b) systolepressure Cuff pressure between 80 and Stethoscope 120 mm Hg Korotkoff sound Figure 15-7 Measuring blood pressure: Sphygmomanometry (a) Cuff pressure > 120 mm Hg Inflatable Silent cuff Pressure gauge (b) Cuff pressure between 80 and Systolic P Stethoscope 120 mm Hg Korotkoff sound (c) diastole pressure Cuff pressure < 80 mm Hg Silent