U-M BIOMEDE 419 - Vascular Biology I - Components of the Vascular System (7 pages)

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Vascular Biology I - Components of the Vascular System



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Vascular Biology I - Components of the Vascular System

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7
School:
University of Michigan
Course:
Biomede 419 - Quant Physiology
Quant Physiology Documents
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BME 419 519 Hernandez 2002 Vascular Biology I Components of the Vascular System Functions of Vascular system 1 Active transport of substances through the body small organisms have mostly passive transport Nutrients glucose ATP Oxygen waste hormones chemical signals host defenses WBC platelets globulins etc 2 Regulation of that flow Arterial shunts to distribute blood flow to organs that need it the most eg blood flow to the brain and heart must be maintained at all costs so in the event of blood loss vasoconstriction occurs Basal tone tonic contraction of vessel smooth muscle in the absence of external stimulation 3 Thermal regulation Blood flow through skin heat radiation cooling quite efficient By redirecting flow you can cool down or heat up internal organs maintenance of homeostasis BME 419 519 Organ Brain Heart Skel Musc Skin Kidney Abd Organs Other Total Hernandez 2002 Distribution of systematic blood flow Flow Rate of Total Flow Rate with at Rest Flow Strenuous Exercise ml min ml min 650 13 750 215 4 750 1 030 20 12 500 430 9 1 900 950 20 600 1 200 24 600 545 10 400 5 000 100 17 500 of Total Flow 4 4 73 11 3 3 2 100 Components of the Cardiovascular System 1 Heart obviously the pump that drives the system more details elsewhere 2 Blood main components a Erythocytes Red Blood Cells Carry oxygen bound to hemoglobin molecules Hematocrit of blood volume made up by erythrocytes b Leukocytes White Blood Cels bind engulf and digest debris c Plasma the solvent Contains mostly water proteins dissolved gasses nutrients hormones waste products d Platelets Responsible for clotting repair of damaged tissue plug for hemorrhages The clotting process consists of a complex cascade of chemical signals 3 Lymphatic system endothelial filtration can produce excess water and other materials mostly protein lymph Parallel vascular system that returns this fluid into the veinous system at the junctions of subclavian and jugular veins Flow is passive powered by muscle contractions and guided by one way valves Proteins go from blood to lymph because of osmotic gradient Need lymphatic system to return them to the blood 4 Vasculature arteries input to tissue and veins output from tissue capillaries site of exchange BME 419 519 Hernandez 2002 b Vascular Components Macroscopic level Distribution of Blood through vascular system and maintain pressure pulsatility etc Components the different types of vessels 1 Aorta arteries very elastic they store the cardiac stroke volume until it can flow through the system As you get further from heart the pressure waves become more smoothed out they act as a low pass filter because of their compliance 2 Arterioles local control of blood flow by regulating the amount of flow to individual organs through arterial sphincters They are responsible for maintaining the peripheral resistance 3 Capillaries Are the site of chemical exchanges between blood and tissue Oxygen nutrients ions Pulmonary vessels are where oxygen enters the blood stream 4 Venules collect capillary blood and direct it into the veins 5 Veins Take the deoxygenated blood back to the heart Very compliant little resistance passive Not much muscle tone The inner walls have pockets that act as one way valves not 100 Return blood flow is often aided by skeletal muscles s actions eg some people faint after standing for a long time because leg muscles help the blood return to the heart 6 Lymphatic system carries interstitial fluid excess protein into the venous return so that they can enter the vascular system Similar to veinous network not identical though Flow is driven by oncotic pressure muscle movement contractions of lymphatic vessels and one way valves Lyphatic system enters veinous system at the junction of sub clvian and jugular veins BME 419 519 Hernandez 2002 BME 419 519 Hernandez 2002 BME 419 519 a Hernandez 2002 Vascular components Microscopic level endothelium connective tissue VSM i Endothelium lining tissue endothelial cells lots of functions Liner for the interior of the blood vessels Non reactive to RBCs Barrier between blood and tissue Materials penetrate tissues through pores 4 nm diameter or junctions between endothelial cells EXCEPT for brain brain blood barrier Passive Transport sum of the following Diffusion J D A dc dx P S Cout Cin hydrostatic pressure pushes fluid out of capillaries strongest osmotic pressure keeps fluid in capillaries Starling Hypothesis transport can be calculated as the sum of all of the above leftovers accumulate in the interstitial space end get taken up by lymphatic system Active as in pinocytosis Angiogenesis generation of new vessels also helps produce VSM Produce vasoconstriction dilation factors that signal VSM to act Endothelial Derived Contracting Factor EDRelaxingF ii Connective Tissues Maintain the vessels in place and provide the structure to support the intra cascular pressure Elastin polypeptide molecules with spring like properties give the tissue its eleasticity stretchable Collagen Fibers another peptide Long Rigid molecules It s used all over the body to give structure Eg fascia tendons iii Vascular Smooth Muscle a Functions b Regulate the diameter resistance to flow of the vessel by constriction dilation Regulates where blood flow goes There can be one or more layers of it around the vessels Wraps around the vessels in a helical pattern Remember scwann cells Slow reaction to signals relative to skeletal muscle Capable of sustaining contractions for extended periods of time Contraction BME 419 519 Hernandez 2002 Passive stretching if increased BP Different from skeletal muscle no clearly defined sarcomeres but still uses sliding filament mechanism driven by phosphorylation of cross bridges this is activated by the presence of Ca ions in the myoplasm Difference from skeletal muscle no troponin this is what forms the cross bridges in skeletal muscle In skeletal muscle Ca ions trigger cross bridge cycling of troponin directly In VSM Ca binds to calmodulin this in turn leads to phosphorylation of myosin light chains cross bridge cycling latch state Can stay contracted with little phosphorylation activity once it gets contracted Easy to maintain tone c Contraction signals Direct factors no intermediaries Hormones epinephrine norepinephrine angiotensis operate on receptor gated Ca channels pharmacological agents receptor gated Ca channels Nervous input voltage gated Ca channels Indirect factors cause endothelial tissue to release contracting relaxing


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