Capillary Exchange Diffusion Most important solute exchange method

Capillary Exchange Diffusion Most important solute exchange method O 2, CO 2, glucose, a. a. , hormones = [ ] gradients Transcytosis Enclosing substances in tiny vesicles. Endocytosis into cells. Bulk Flow Important regulation of relative volumes of blood and interstitial fluid Plasma solutes cross capillary walls Filtration Blood-brain barrier = exception Reabsorption

Capillary Exchange Blood hydrostatic pressure pushes fluid out of capillaries (filtration). Blood colloid osmotic pressure pulls fluid into the capillaries (reabsorption).

Figure 21. 7 Capillary exchange

Hemodynamics Factors affecting BF 4 main factors SV, HR, Pressure, Resistance

Blood Flow Ø Volume of blood flowing through any tissue in a given time period. Ø BF = BV m. L/min Ø Total blood flow = cardiac output Ø BF= CO; (SV X HR) Ø The same factors that change CO change BF Ø Stroke volume: preload and contractility Ø Heart rate: nervous system and chemicals

Blood Flow Ø Distribution of CO to tissues depends on: Ø Pressure difference Ø Vascular resistance Ø 4 factors affecting BF Ø Ultimately controlled by contractility (large role) and endocrine system NE and E (lesser role)

Blood Pressure exerted by blood on the wall of an artery during ventricular systole and diastole. Pulse pressure Difference between systolic and diastolic pressures Mean The arterial pressure average BP in arteries

Blood Pressure BP CO , VR , BV (HR, SV) Blood itself has a role in BP More blood = éBP Less blood = êBP BV Blood doping Dehydration Injury

Blood Pressure 1. BP 2. BP (MAP) = CO x R If resistance remains steady éCO = éBP êCO = êBP depends on total BV in system éBV = éBP êBV = êBP

Vascular Resistance Opposition to flow due to friction between blood & vessel walls 3 factors: Diameter of blood vessels Blood viscosity Total blood vessel length

Vascular Resistance Diameter of blood vessels Resistance is inversely proportional to the 4 th power of the radius of the blood vessel R 1/ r 4 The smaller the radius of the vessel = the greater the resistance it offers to BF Blood Viscosity Total blood vessel length Resistance is directly proportional to blood vessel to viscosity length The greater the Longer the vessel, viscosity, the greater resistance to greater the blood that flows resistance through it. Pathology Hematocrit

Systemic Vascular Resistance Total peripheral resistance All vascular resistances offered by systemic blood vessels Most in arterioles, capillaries, venules ** Arterioles

Figure 21. 9 Venous Return Pressure gradient (contractions of L. V. ) between venules and R. A. 1. Valves 2. Skeletal Muscle Pump* 3. Respiratory Pump*

Figure 21. 10

Figure 21. 11

Blood Vessel Topics 1. Components of the blood vessel system 2. Basic structures of blood vessels 3. Blood distribution 4. Capillary exchange 5. Factors affecting blood pressure and flow 6. Control of blood pressure and flow 7. Circulatory routes

Figure 21. 12

Figure 21. 13

Blood Vessel Topics Circulatory Routes – in lab Figure 21. 17

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