Blood Distribution

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Blood Distribution

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University of Southern California
Bisc 307l - General Physiology
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BISC 307L 1st Edition Lecture 28 Current Lecture  Blood Flow to Organs at Rest o o Left heart puts out blood that is being distributed to the various organ systems and shows the fraction that goes to the various systems o The block points: percent of the total cardiac output that goes to the brain o The right heart pumps out one hundred percent of what it receives from the left (starling law) – Must have same cardiac output o Since closed circuit if this wasn’t the case then this would cause accumulation of blood somewhere else in the system o Plot of normalized cardiac outputs o The kidney receives the most bloodfunction to continuously filter and adjust the composition of the blood (receives high pressure blood) o Regulation by vasoconstriction and vasodilation of cardiac output received by the various organs. This can be adjusted and redirected  Blood Pressure, Velocity and CSA o o Relationships between BP blood velocity and cross sectional area o Rate at which fluid flows is the same at all points in the tube but in order for this to happen the velocity must be fastest in the small diameter and slower in the big part o The most narrow places move the fastest but it is the same amount moving through o Total cross-sectional area of all the blood vessels (chart on right) and you see that the arteries have large diameter so their cross-sectional area total is small and the capillaries have total largest cross sectional area and so the flow velocity increases in the veins and slow in the capillaries even though the pressure falls in the capillaries. This facilitates the exchange of materials  Cappilarries o o Single layer of endothelial cells and a mesh of fibrous cells that fill in the gaps. The gaps are pores so fluid can leak out o The endothelial cells themselves have pores in adjacent to the junctions in between the endothelial cells o Can actively transport materials across the cells by transcytosis where there is endocytosis on one side and exocytosis on the other o Implication for pores: in kidney and digestive tract important for fast transport of material o Capillaries in the brain and spinal cord DO NOT have these open junctions but rather are sealed to each other by tight junctionsform the blood brain barrier. Material must diffuse across the endothelial cell or transported by active and passive transport o Consider the forces that push through these holesalways leaking fluid.  Fluid Exchange across capillaries

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