Section 3 Physiology of the Blood Vessels,. Functional Anatomy of Blood vessels （各类血管的结构功能特点）,1.Windkessel vessel(弹性贮器血管) 2.Distribution vessel(分配血管) 3.Resistance vessel(阻力血管) 4.Exchange vessel（交换血管） 5.Capacitance vessel （容量血管） 6. Shunt vessel (短路血管),1.Windkessel vessel (弹性贮器血管)aorta to buffer variation of BP。,Windkessel Vessel - Aorta and big arteries. They transiently store blood during systole, and then shrink to produce onward blood flow during diastole.,they convert the sharp pressure fluctuations in the left ventricle (0 to 120 mmHg) into much smaller pressure fluctuations in the arteries (80 to 120 mmHg). And convert the intermittent ventricular ejection into continuous blood blood in the vessels This function of large arteries is known as Windkessel effect.,2. distribution vessel,2. Distribution Vessel Middle arteriesThese arteries are rich in smooth, which will systole or diastole under some physical and chemical factors. Together with resistance vessels, they match the blood flow to different organs with their requirements.,Distribution of Cardiac Output,3.Resistance vessel (阻力血管) small artery the role in blood distribution venules.,The amount of blood flowing through a particular capillary bed is determined in part by the action of the precapillary sphincter of muscle. These muscles allow only 5% - 10% of the capillary in bed skeletal muscles, for example, to be open at rest.,4. Precapillary Sphincter muscle-,4.Exchange vessel(交换血管Capillary; pores function: formation of interstitial fluid.,Exchange Vessel Capillary the walls of capillaries are composed of only one cell layer a simple squamous epithelium, or endothelium. The absence of smooth muscle and connective tissue layers permits a more rapid transport of materials between the blood and the tissues.,5.Capacitance vessel （容量血管）venous system; large volume and extensibility; sympathetic nerve;function:to store blood & to regulate venous return.The walls of the venules are also thin and easily distended. The walls of veins are thin, but its lumen are larger.,Structurally, veins have a large diameter but a thin wall, which includes a thin muscle coat. The number veins is about twice as much as the number of arteries, The large number and cross sectional area gives them an enormous capacity to hold blood.,Further, the great distensibility of veins makes their capacity adjustable.In times of need, a considerable amount of blood can be squeezed from the veins to areas where it may be be needed.,Most of the time, veins hold more than half the blood volume . That is why veins are known as capacitance vessels.,6. Shunt vessel Arteriovenous AnastomosesFunction: Regulates the body temperature,.Hemodynamics (血流动力学) 1.BIood FIow (血流量,容积速度 Q) Concept:It is a quantity of bled that passes a given cross section of blood vessel per minute.单位时间内流过血管某一截面的血量。 Poseuilles Law (泊肃叶定律)Q=(P1-P2)r4/8LThe overall blood flow in the systemic circulation is identical to the cardiac output,(2) Factors determining blood flow interrelationships among blood flow(Q), pressure(P) and resistance(R). 1) P: the pressure difference between the two ends of the vessels,; 2) R: frictional force produced when blood fIows through blood vessels. Q = P / R,Q =,P1 P2,R,血流速度(V ) = Q/A V主V毛,A,2.血流速度 (velocty) 血液中的一个质点在血管内移动的线速度。 与血流量成正比，与横截面积成反比。aorta velocity 20cm/s, Capillary velocity 0.03cm/s segment inversely,The velocity of blood flow in each segment of the circulation is inversely proportional to its cross-sectional area.,Laminar flow and turbulent flow Laminar flow blood flows in streamlines with each layer of blood remaining the same distance from the wall;,Laminar flow,Turbulent flow blood flow in all directions in the vessel and continually mixes within the vessel.,C, constriction; A, anterograde; R, retrograde,because ofthe velocity of blood flow is too great, is passing by an obstruction, making a sharp turn, passing over a rough surface),Re=VD/Re2000 Turbulent flow,3.Resistance(血流阻力,R)It is frictional force produced when blood fIows through blood vessels.Q= （P1- P2)r4 / 8 L Q= (P1- P2) /R 8 LR= , r 4,R= 8 L/ ( r 4) R1/r4 Note that the resistance (R) of a vessel is directly proportional to the blood viscosity () and length (l) of the vessel, but inversely proportional to the fourth power of the radius ( r ). the diameter of a blood vessel plays by far the greatest role of all factors in determining the resistance ( R ) of blood flow.,4.Blood Pressure (血压, BP) It is a force exerted by the blood against unit area of the vascular wall. Blood Pressure is stored energy (potential energy) Q = P / R P = Q . R,Major Theme:Blood Pressure is stored energy (potential energy) Physical Definition: Force per unit area Pressure = dyne/cm2; 1mmHg=0.133kPa or 133Pa,. Arterial Blood Pressure and arterial pulse （）Arterial Blood Pressure,