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SECTON IV CIRCULATION

SECTON IV CIRCULATION. Chapter 12~14. CHAP 12 DYNAMICS OF BLOOD AND LYMPH FLOW. CHAP 12 DYNAMICS OF BLOOD AND LYMPH FLOW. 12.1 INTRODUCTION 12.2 FUNCTIONAL MORPHOLOGY OF BLOOD VESSELS 12.3 BIOPHYSICAL CONSIDERATIONS 12.4 ARTERIAL AND ARTERIOLAR CIRCULATION

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SECTON IV CIRCULATION

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  1. SECTON IVCIRCULATION Chapter 12~14

  2. CHAP 12DYNAMICS OF BLOOD AND LYMPH FLOW CHAP 12 DYNAMICS OF BLOOD AND LYMPH FLOW 12.1 INTRODUCTION 12.2 FUNCTIONAL MORPHOLOGY OF BLOOD VESSELS 12.3 BIOPHYSICAL CONSIDERATIONS 12.4 ARTERIAL AND ARTERIOLAR CIRCULATION 12.5 CAPILLARY CIRCULATION 12.6 LYMPHATIC CIRCULATION AND INTERSTITIAL FLUID VOLUME 12.7 VENOUS CIRCULATION Cardiovescular system: B

  3. 12.1 INTRODUCTION • The blood vessels are a closed system of conduits • Blood flows: depended on different pressure • Primarily because of the forward motion imparted to it by the pumping of the heart • Diastolic recoil of the walls of the arteries • Compression of the veins by skeletal muscles • Negative pressure in the thorax during inspiration also move the blood forward • Resistance to flow • Viscosity of the blood • Diameter of the vessels, principally the arterioles Cardiovescular system: B

  4. 12.2 FUNCTIONAL MORPHOLOGY OF BLOOD VESSELS • Windkessel vessels：large arteries • Distribution vessels: arterial systemic vessels • Resistance vessels: arterioles • Exchange vessels: capillaries • Capacitance vessels: venous systemic vessels • Shunt vessels: arteriovenous anastomosis Cardiovescular system: B

  5. 12.3 BIOPHYSICAL CONSIDERATIONS 12.3.1 Pressure, flow, and resistance • Basic concepts of hemodynamics F=P/R • F: blood flow • P: blood pressure gradient • R: blood flow resistance Cardiovescular system: B

  6. 12.3 BIOPHYSICAL CONSIDERATIONS • Blood flow Flow rate=volume / second F (mL/s) ＝ P/R ＝ K(P1－P2)r4/L ＝(P1－ P2)r4/8L r: radiusof blood vessels L: length of blood vessels : blood viscosity Cardiovescular system: B

  7. P1 P2 P1 P2 12.3 BIOPHYSICAL CONSIDERATIONS Blood flow (F)is directly proportional to the pressure gradient (P, not P)and inversely to the resistance (R) P=(100－10)mmHg =90mmHg Flow=10mL/min P=(500－410)mmHg =90mmHg Flow=10mL/min Cardiovescular system: B

  8. P r1=2 F1=16 r2=1 F2=1 12.3 BIOPHYSICAL CONSIDERATIONS • Blood flow resistance R＝F/P ＝8L/r4 • Blood flow types and resistance Cardiovescular system: B

  9. 12.3 BIOPHYSICAL CONSIDERATIONS • Blood pressure Side pressure: force /area of vessels P＝F·R F：Cardiac Output R：8L/r4 1mmHg＝0.133 kPa ＝1333 dyn·cm-2 1kPa＝7.5mmHg Cardiovescular system: B

  10. 12.3 BIOPHYSICAL CONSIDERATIONS 12.3.2 Average velocity V (cm/s) ＝ Q/A V:Velocity Q:flow A:the area of the conduit • Aorta: 40cm/s • Capillaries: 0.07cm/s the capillarieshave 1000 times the total cross-sectional area of the aorta Cardiovescular system: B

  11. 12.3 BIOPHYSICAL CONSIDERATIONS 12.3.3 Viscosity and resistance The resistance to blood flow is determined by the : • Radius of the blood vessels (vascular hindrance): resistance vessels • Viscosity of the blood: dependent on the hematocrit Cardiovescular system: B

  12. 12.3 BIOPHYSICAL CONSIDERATIONS 12.3.4 Law of Laplace Cardiovescular system: B

  13. 12.4 ARTERIAL AND ARTERIOLAR CIRCULATION 12.4.1 Arterial pressure • Formation of arterial blood pressure: dependent on relationship of the blood volume/vessel capacity • Blood filling in the system • Cardiac output + recoil of arterial wall • Peripheral resistance Cardiovescular system: B

  14. 12.4 ARTERIAL AND ARTERIOLAR CIRCULATION 12.4.2 Normal arterial pressure • Measurement of systemic arterial pressure: aortic pressure • Systolic pressure (SP): 120mmHg • Diastolic pressure (DP): 70mmHg • Pulse pressure • Mean arterial pressure (MAP) • MAP=DP + 1/3(SP－DP) Cardiovescular system: B

  15. 12.4 ARTERIAL AND ARTERIOLAR CIRCULATION 12.4.3 Factors affecting arterial pressure • Stoke volume • Heart rate • Peripheral resistance • Compliance of aorta and large artery • Circulatory blood volume/Capacity of vessels Cardiovescular system: B

  16. 12.4 ARTERIAL AND ARTERIOLAR CIRCULATION Cardiovescular system: B

  17. 12.5 CAPILLARY CIRCULATION • Micro-circulation Between arterioles and venules About capillary bed blood supply Cardiovescular system: B

  18. 12.5 CAPILLARY CIRCULATIONv • Microcirculation channels and theirs main functions • Circuitous channels Exchange of metabolites • Thoroughfare channel Rapid return blood into circulation • A-V shunt Regulation of circulating blood volume and temperature Cardiovescular system: B

  19. 12.5 CAPILLARY CIRCULATION Structure of capillary Cardiovescular system: B

  20. 12.5 CAPILLARY CIRCULATION 12.5.1 Capillary pressure and flow • Capillary pressures vary considerably Typical values capillaries： • 32 mm Hg at the arteriolar end • 15 mm Hg at the venous end • Blood flow • The capillaries are short • Velocity: about 0.07 cm/s • transit time from the arteriolar to the venular end is 1-2 seconds Cardiovescular system: B

  21. 12.5 CAPILLARY CIRCULATION • Exchange of substances • Diffusion Concentration gradient Permeability of capillary wall • Filtration and osmosis Hydrostatic pressure gradient and colloid osmotic pressure gradient • Vesicular transport Endocytosis and exocytosis Cardiovescular system: B

  22. 12.5 CAPILLARY CIRCULATION 12.5.2 Equilibration with interstitial fluid • Capillary filtration and osmosis • Interstitial fluid from filtrated plasma (0.3% plasma) Cardiovescular system: B

  23. 12.5 CAPILLARY CIRCULATION Formation and return of interstitial fluid Capillary Venular end Arteriolar end Capillary hydrostatic pressure Colloid osmotic pressure of plasma Pc p if Pif Colloid osmotic pressure of intestinal fluid intestinal fluid hydrostatic pressure Cardiovescular system: B

  24. 12.5 CAPILLARY CIRCULATION • V＝Kf [ (Pc＋if)－(p＋Pif) ] • V: formatting volume of interstitial fluid • Kf: filtration coefficient----permeability of capillaries, filtration areas • (Pc＋ if)－(p＋Pif): effective filtration pressure (EFP) or net filtration pressure (NFP) At arteriolar end, EFP=＋10mmHg, →net filtration net filtration≈~20L /d At venular end, EFP=－8mmHg, →net return net return≈~18L/d Lymphatic return ≈~2L/d Cardiovescular system: B

  25. 12.6 LYMPHATIC CIRCULATION AND INTERSTITIAL FLUID VOLUME 12.6.1 Lymphatic circulation • From extra fluid and to drain through them back into the blood • Lymph flow is 2~4L/24hr • Lymphatic vessels • Initial lymphatics • Collecting lymphatics Cardiovescular system: B

  26. 12.6 LYMPHATIC CIRCULATION AND INTERSTITIAL FLUID VOLUME • Function of the lymphatic system • Reclaiming protein and absorbing nourishment • Cleaning the RBC、bacterium and foreign substance • Balancing the formation and absorption of interstitial fluid Cardiovescular system: B

  27. 12.6 LYMPHATIC CIRCULATION AND INTERSTITIAL FLUID VOLUME 12.6.2 Interstitial fluid volume The amount of fluid in the interstitial spaces depends on the: • Capillary pressure: ratio of precapillary to postcapillary venular resistance • Interstitial fluid pressure • Colloid osmotic pressure • Capillary filtration coefficient • Number of active capillaries, • Lymph flow • Total ECF volume Cardiovescular system: B

  28. 12.6 LYMPHATIC CIRCULATION AND INTERSTITIAL FLUID VOLUME • Edema • Increased filtration pressure:Arteriolar dilation; Venular constriction; Increased venous pressure (heart failure, incompetent valves, venous obstruction, increased total ECF volume, effect of gravity, etc) • Decreased osmotic pressure gradient acrosscapillary:Decreased plasma protein level; Accumulation of osmotically active substances in interstitial space • Increased capillary permeability:Substance P; Histamine and related substancesKinins, etc • Inadequate lymph flow Cardiovescular system: B

  29. 12.7 VENOUS CIRCULATION 12.7.1 Venous pressure and flow • Venous pressure • Peripheral venous pressure (PVP) Venules: 12-18 mm Hg larger veins: 5.5 mm Hg Gravitational force ← posture • Central venous pressure (CVP) 4.6 mm Hg (4~12cmH2O) Dependent on cardiac ejection function and venous return volume Cardiovescular system: B

  30. 12.7 VENOUS CIRCULATION • Venous blood flow • From the venules to the large veins, its average velocity increases • In the great veins, the velocity of blood is averaging about 10 cm/s (about 1/4 in the aorta) Cardiovescular system: B

  31. 12.7 VENOUS CIRCULATION 12.7.2 Factors affecting venous flow • Cardiac contraction • Muscle pump • Thoracic Pump (respiratory “pump”) Cardiovescular system: B

  32. CHAP 13CARDIOVASCULAR REGULATORY MECHANISMS CHAP 13 CARDIOVASCULAR REGULATORY MECHANISMS 13.1 INTRODUCTION 13.2 SYSTEMIC REGULATION BY THE NERVOUS SYSTEM 13.3 SYSTEMIC REGULATION BY HORMONES 13.4 SUBSTANCES SECRETED BY THE ENDOTHELIUM 13.5 LOCAL REGULATION Cardiovescular system: B

  33. 13.1 INTRODUCTION • Regulatory mechanisms • Neural regulation: cardiovascular reflex • Humoral regulation: active substances • Autoregulation • Regulatory effects • Altering cardiac output • Changing the diameter of the resistance of vessels • Altering the amount of blood pooled in the capacitance vessels Cardiovescular system: B

  34. 13.1 INTRODUCTION • Regulatory significations • To maintain homeostasis of blood pressure • To redistribute the blood supply • To maintain blood volume adequately Cardiovescular system: B

  35. 13.2 SYSTEMIC REGULATION BY THE NERVOUS SYSTEM 13.2.1 Vessels innervation and vasomotor control • Noradrenergic fibers end on vessels in all parts of the body Sympathetic vasoconstrictor fibers activities • NA→-adrenergic receptor →vasoconstriction →2-adrenergic receptor→vasodilation • Transmitter released by varicosities • Tonic discharge: vasodilation or vasoconstriction • To increase flow resistance——determining the MAP and the organic blood flow Cardiovescular system: B

  36. 13.2 SYSTEMIC REGULATION BY THE NERVOUS SYSTEM • Distribution on the small vessels Cardiovescular system: B

  37. 13.2 SYSTEMIC REGULATION BY THE NERVOUS SYSTEM • Cholinergic fibers end on vessels in parts of the organs Sympathetic and parasympathetic vasodilator fibers activities • ACh→M-receptor → vasodilation • No tonic discharge • To increase blood flow of the special region • Noncholinergic, nonadrenergic fibers NO, peptide, purine,… Cardiovescular system: B

  38. 13.2 SYSTEMIC REGULATION BY THE NERVOUS SYSTEM • Hormones Ad, Ang II, VP, ET-1, ANP, NO,… • Local controls--flow autoregulation • Active hyperemia: chemical factors O2↓, CO2, H+, adenosine, K+, PGs,… • Metabolic product • Myogenic response: intrinsic tone: Arteriolar smooth muscle possesses spontaneous activity (independent) • Response to injury Cardiovescular system: B

  39. 13.2 SYSTEMIC REGULATION BY THE NERVOUS SYSTEM 13.2.2 Cardiac innervation • Cardiac sympathetic nerves: noradrenergic fibers • Tonic discharge • To increase the cardiac rate (positive chronotropic effect), A-V conduction rate (positive dromotropic effect) and the force of cardiac contraction (positive inotropic effect) • To inhibit the effects of vagal stimulation (probably by neuropeptide Y ) Cardiovescular system: B

  40. 13.2 SYSTEMIC REGULATION BY THE NERVOUS SYSTEM • Cardiac vagal nerves: cholinergic fibers • Tonic discharge (vagal tone) • To decrease the heart rate (negative chronotropic effect) and A-V conduction rate (negative dromotropic effect) Cardiovescular system: B

  41. 13.2 SYSTEMIC REGULATION BY THE NERVOUS SYSTEM • Medullar cardiovascular center • Vasoconstrictor area: RVLM • Vasodilator area: CVLM • Cardioinhibitory area: ambiguous nucleus • Relay station of afferent nerve: NTS • Cardiovascular center over the medullar • Brain stem • Hypothalamus • Cerebral cortex Cardiovescular system: B

  42. 13.2 SYSTEMIC REGULATION BY THE NERVOUS SYSTEM • The baroreceptor reflex activity Cardiovescular system: B

  43. 13.2 SYSTEMIC REGULATION BY THE NERVOUS SYSTEM • Physiological significance of baroreceptor reflex • Monitoring the arterial pressure • Maintaining the arterial pressure homeostasis • Baroreceptor resetting (in chronic hypertension) Cardiovescular system: B

  44. 13.2 SYSTEMIC REGULATION BY THE NERVOUS SYSTEM 13.2.4 Effects of chemoreceptor stimulation on the vasomotor area • Chemoreceptors: carotid and aortic bodies • Exert their main effect on respiration • Also converge on the vasomotor area: peripheral vasoconstriction and bradycardia Cardiovescular system: B

  45. 13.3 SYSTEMIC REGULATION BY HORMONES 13.3.1 Kinins • Kinins: vasodilator peptides • Bradykinin • Lysylbradykinin (kallidin) Cardiovescular system: B

  46. 13.3 SYSTEMIC REGULATION BY HORMONES • Kallikreins: proteases types of kallikreins • plasma kallikrein: kallikreinogen activation by factor XIIa • Acting on HMWK to form bradykinin • Tissue kallikrein: sweat and salivary glands, pancreas, prostate, intestine, and kidneys • Acting on HMWK to form bradykinin and LMWK to form lysylbradykinin. When activated, plasma kallikrein Cardiovescular system: B

  47. 13.3 SYSTEMIC REGULATION BY HORMONES • Actions of the kinins resemble those of histamine • Visceral smooth muscle contraction • Vascular smooth muscle relaxiton (via NO)：↑blood flow of exocrine glands • Capillary permeability increase • Bradykinin receptors: G proteins coupling receptors • B1: to mediate the pain-producing effects • B2: homology to the H2 receptor (arousal, sexual behavior, pituitary hormones secretion, blood pressure, drinking, and pain thresholds) Cardiovescular system: B

  48. 13.3 SYSTEMIC REGULATION BY HORMONES 13.3.2 Adrenomedullin • Depressor polypeptide: by increasing production of NO • To inhibit aldosterone secretion in salt-depleted animals and appears to produce its depressor effect Cardiovescular system: B

  49. 13.3 SYSTEMIC REGULATION BY HORMONES 13.3.3 Natriuretic hormones ANP, BNP and CNP • The atrial natriuretic peptide (ANP) secreted by the myocardium • Antagonizes the action of various vasoconstrictor agents and lowers blood pressure • The natriuretic Na+-K+ATPase inhibitor (endogenously produced ouabain) Cardiovescular system: B

  50. 13.3 SYSTEMIC REGULATION BY HORMONES 13.3.4 Circulating vasoconstrictors • Vasopressin (ADH) is a potent vasoconstrictor • Norepinephrine has a generalized vasoconstrictor action • Angiotensin II has a generalized vasoconstrictor action Cardiovescular system: B

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