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20 Vessels and Circulation notes ada 2.pptx
- 1. Vascular transport supportslife by distributing and facilitating the exchange of gases, nutrients, and other substances with body cells. Vascular impairment can result in tissue injury, impaired metabolism, and system failure. The Cardiovascular System: Blood Vessels and Circulation
- 2. Artery – awayfrom heart Vein – toward heart Systemic circuit: oxygen-rich blood to body tissues, oxygen- poor blood from tissues to RA Pulmonary circuit: oxygen-poor blood from systemic circulation to lungs for gas exchange; oxygen-rich blood to LA Structure and Function of Vessels
- 3. • Lumens • Wallsof living cells and connective tissues • 3 distinct tissue layers (tunics) Shared Structures of Vessels
- 4.
- 5. • Epithelial andconnective layers • Lined with endothelium • Endothelium continuous throughout vascular system • Endothelins can constrict vessels • Basal lamina • Binds endothelium to connective tissue • Strength, flexibility, permeability • Internal elastic membrane • Large arteries only • Tunica media boundary Structure and Function of Vessels – Tunica Intima
- 6. • Thick, smoothmuscle and connective tissue • Circular elastic fibers • Vasocontstriction • Vasodilation • Nervi vasorum • Longitudinal muscle • External elastic membrane • Separates tunica media from externa Structure and Function of Vessels – Tunica Media
- 7. • Mostly collagenwith some elastic • Thickest layer in veins and some arteries • Outer layer contiguous with connective tissue for stability Structure and Function of Vessels – Tunica Externa
- 8. • Arteries –away from heart • Elastic arteries • Conducting arteries • Closest to heart • High percentage of elastic fibers = strong recoil Structure and Function of Arteries- Elastic
- 9. • Arteries –away from heart • Muscular arteries • Distributing arteries • Vasoconstriction • Decreased elastic = decreased ability to expand • No “line of demarcation” Structure and Function of Arteries- Muscular
- 10. • Arteries –away from heart • Arterioles • Lead to capillaries • Very thin layers • Resistance vessels • Vascular tone • Primary site of pressure regulation Structure and Function of Arteries- Arterioles
- 11. Capillaries – perfusion,microcirculation • Continuous • Most vascular tissue • Complete endothelium • Tight junctions • Transport vesicles (brain is exception) • Blood-brain barrier Structure and Function of Capillaries- Continuous
- 12. Capillaries – perfusion,microcirculation • Fenestrated • Pores (fenestrations) in addition to tight junctions • Permeable to larger molecules • Small intestine, kidneys, choroid plexuses Structure and Function of Capillaries- Fenestrated
- 13. Capillaries – perfusion,microcirculation • Sinusoidal • Most permeable; occurs in specialized locations only Structure and Function of Capillaries- Sinusoidal
- 14. Capillaries – perfusion, microcirculation •Metarterioles • Similar to both arterioles and capillaries • Tunica media discontinuous; rings of smooth muscle sphincters • Lead to capillary beds • Diapedesis • Perfusion Structure and Function of Metarterioles and Capillary Beds
- 15. Venules • Postcapillary • Multiplevenules = veins • Endothelium, thin muscle, outer connective tissue • Diapedesis Structure and Function of Veins- Venules
- 16. Veins – bloodtoward the heart • Thin walls • Large, irregular lumens • Low pressure • Valves for unidirectional flow • Skeletal muscle helps venous return Structure and Function of Veins- Veins
- 17. • Pooling ofblood leads to increase in interstitial fluid due to pressure • Hypertension, heart failure, renal failure • Symptom, not a disease Structure and Function of Vessels- Edema
- 18. • Defective valvesallow for blood accumulation • Veins distend and twist • Can be painful • Worsen over time Structure and Function of Vessels – Varicose Veins
- 19. • Systemics contain64% of blood volume • Capacitance – ability to distend even at low pressure Structure and Function of Vessels – Veins as Blood Reservoirs
- 20. • Blood Flow– movement through vessel, tissue, or organ • Volume / time • Down a pressure gradient • Resistance • Blood pressure = hydrostatic • Systemic arterial • mm Hg • Usually obtained via brachial artery Blood Flow, Pressure, and Resistance- Flow
- 21. Arterial Blood Pressure– Systolic and Diastolic Pressures • Systolic: ventricular contraction • Diastolic: ventricular relaxation • Pulse Pressure: difference b/t systolic and diastolic • Should be 25% of systolic • Mean Arterial Pressure: “average” pressure of arterial blood Blood Flow, Pressure, and Resistance- Pressure
- 22. Pulse – expansionand recoil from elastic fibers in arteries • Diminishes over distance from heart • Measures HR • Strength indicative of ventricular contraction and CO Blood Flow, Pressure, and Resistance- Pulse
- 23. • Sphygmomanometer: cuff attachedto measuring device • Sounds of Korotkoff: turbulent blood flow; 1st sound is systolic, 2nd is diastolic Blood Flow, Pressure, and Resistance- Measurement of Blood Pressure
- 24. • Cardiac output •Compliance • Volume of blood • Viscosity of blood • Blood vessel length and diameter Blood Flow, Pressure, and Resistance – Variables Affecting Blood Pressure
- 25. • Cardiac Output •Flow through ventricles • L / min • Varies directly with heart rate and stroke volume Blood Flow, Pressure, and Resistance – Variables Affecting Blood Pressure: Cardiac Output
- 26. • Compliance: abilityto expand to accommodate increased content • Veins are more compliant than arteries • Decreased compliance = decreased blood flow Blood Flow, Pressure, and Resistance – Variables Affecting Blood Pressure: Compliance
- 27. • Poiseuille’s equationin a nutshell: • Blood flow = Δ P/ Resistance • Resistance = Δ P/ Blood flow • Poiseuille’s original equation related 3 variables: viscosity, vessel length, and radius • Viscosity and vessel length change slowly • Radius values can be changed rapidly • Even small changes in r will dramatically impact flow Blood Flow, Pressure, and Resistance – Variables Affecting Blood Pressure: Do the Math!
- 28. • Hypovolemia: lowblood volume • Bleeding, dehydration, vomiting, severe burns, hypertension meds • 10-20% blood loss • Hypervolemia: excessive fluid volume • Water, sodium retention • Heart failure, liver disease, kidney disease, hyperaldosteronism, steroid treatments Blood Flow, Pressure, and Resistance – Variables Affecting Blood Pressure: Volume
- 29. • Resistance =8ηλ / πr4 • η = viscosity, λ = vessel length, and • r = vessel radius • Viscosity is directly proportional to resistance and indirectly proportional to flow. Blood Flow, Pressure, and Resistance – Variables Affecting Blood Pressure: Viscosity
- 30. • Resistance =8ηλ / πr4 • η = viscosity, λ = vessel length, and • r = vessel radius • Length is directly proportional to resistance due to increased surface area • 150 lbs = 60,000 miles of vessels! • Every 10 lbs extra adds 2 – 4K miles • Slow change Blood Flow, Pressure, and Resistance – Variables Affecting Blood Pressure: Length and Diameter
- 31. • Resistance =8ηλ / πr4 • η = viscosity, λ = vessel length, and • r = vessel radius • Diameter is inversely proportional to resistance • Vascular tone is primary determinant • May change frequently throughout the day • R = 1/ r4 ; slight changes in diameter have dramatic results Blood Flow, Pressure, and Resistance – Variables Affecting Blood Pressure: Diameter and Resistance
- 32. Vessel Diameter andTotal Area in Blood Flow and Pressure
- 33. • Reduced compliance •Endothelial injury • High glucose • Infection • Tobacco • Excessive lipids • Emboli • Sudden heart attack or stroke • Ischemia • Hypoxia Blood Flow, Pressure, and Resistance- Arteriosclerosis
- 34. • Management • Lifestylechanges • Angioplasty • Endartectomy • Coronary bypass Blood Flow, Pressure, and Resistance – Arteriosclerosis Management
- 35. Venous pressure mustexceed atrial pressure; 2 factors help maintain the pressure gradient. • Atrial Pressure • Low during diastole • Physiologic “pumps” • Skeletal muscle • One-way valves • Respiratory • Increase in thoracic volume = lower pressure and increased flow into thoracic veins The Cardiovascular System: Venous System and Atrial Pressure
- 36. Why are militaryrecruits trained to stand with their knees slightly bent? Venous pressure must exceed atrial pressure; 2 factors help maintain the pressure gradient. • Atrial Pressure • Low during diastole • Physiologic “pumps” • Skeletal muscle • One-way valves • Respiratory • Increase in thoracic volume = lower pressure and increased flow into thoracic veins The Cardiovascular System: Venous Return
- 37. • Diameter increasesfrom smaller to larger, but cross sectional area decreases • From venules to veins, pressure decreases but velocity increases • Any action increasing venous flow will increase venous return The Cardiovascular System: Pressure Relationships in the Venous System
- 38. • Unlike arterialconstriction, venous constriction increases flow • Smooth muscle contraction = more rounded lumen = decreased resistance • Venoconstriction = increased blood return to heart = increased preload / stretch The Cardiovascular System: Vasoconstriction
- 39. • Filtration: movement fromhigher pressure in capillary to lower pressure in tissues • Reabsorption: movement from higher pressure in tissues to lower pressure in capillaries Bulk Flow: mass movement of fluids through capillary beds and tissues The Cardiovascular System: Hydrostatic Pressure
- 40. • Blood hydrostatic pressure(BHP) • Capillary hydrostatic pressure (CHP) • Interstitial fluid hydrostatic pressure (IFHP) Hydrostatic pressure: pressure of any fluid enclosed in a space; force exerted on vessel walls The Cardiovascular System: Forces Favoring Filtration and Reabsorption
- 41. • Plasma proteins,not formed elements, determine osmotic gradient • Form a colloid rather than solution • Blood colloidal osmotic pressure (BCOP) • Interstitial fluid colloidal osmotic pressure (IFCOP) Osmotic pressure: pressure driving reabsorption; draws fluid back into capillary; determined by osmotic gradients The Cardiovascular System: Filtration , Reabsorption, and Lymphatics
- 42. • Overall CHPis higher than BCOP • More net fluid exits capillaries than is reabsorbed • 24 L / day are filtered, 20.4 L / day reabsorbed • • Lymph capillaries pick up excess and return recycled blood plasma to circulation The Cardiovascular System: Role of Lymphatics
- 43. Blood flow iscontinuously reallocated depending upon tissue needs. • 3 mechanisms ensure adequate blood flow, pressure, distribution, and perfusion: • Neural • Endocrine • Autoregulatory The Cardiovascular System: Regulation
- 44. • Cardiovascular Centersin the Brain • Medulla oblongata • Clusters of anatomically indistinct neurons with independent functions • Cardioacceleratory center • Cardioinhibitory center • Vasomoter center • Cholinergic neurons • ACh prompts release of NO • Release NE • Release NO The Cardiovascular System: Neural Regulation- Brain
- 45. • Baroreceptor Reflexes •Aortic sinuses • Ascending aorta just superior to aortic valve • Carotid sinuses at base of internal carotid arteries • Low-pressure receptors in venae cavae and right atrial walls The Cardiovascular System: Neural Regulation- Baroreceptors
- 46. • Chemoreceptor Reflexes •Close to baroreceptors in aortic and carotid sinuses • Monitor oxygen, carbon dioxide, and pH • Increases in CO2 = increase in cardiac output • Respiratory system must comply with changing chemical demands • Limbic, sympathetic and parasympathetic NS plays role The Cardiovascular System: Neural Regulation- Chemoreceptors
- 47. The Cardiovascular System:Endocrine Regulation
- 48. The Cardiovascular System:Autocrine Regulation of Perfusion • Chemical Signals – work at level of precapillary sphincters • Sphincters open in response to: Decreased oxygen, increased CO2, lactic acid, or other metabolic by-products (falling pH), histamine, increased body temperature • These conditions also release NO • Contraction is triggered by opposite conditions • Myogenic Response – level of smooth muscle stretch in arteriole walls; protects against dramatic fluctuations • Stabilizes blood flow to capillary network • Low flow = little stretch = vasodilation and increase in flow • High flow = more stretch = vasoconstriction to reduce flow
- 49. • Heart • Increasescardiac output, size, mass, and efficiency of the heart • Tissues • Perfusion increases • Vessels • Venous return increases, so preload rises and heart rate is lowered • Decreases plaque formation and lowers cholesterol The Cardiovascular System: Effects of Exercise on Vascular Homeostasis
- 50. • Hypertension • Chronicallyelevated blood pressure (140/90 or greater) • “Silent Killer” • Can lead to heart attack, stroke, aneurism, peripheral arterial disease, kidney disease • Hemorrhage • Uncontrolled blood loss • Increases cardiac output, vasoconstriction • Endocrine response to try and restore volume The Cardiovascular System: Clinical Considerations in Vascular Homeostasis
- 51. The Cardiovascular System:Clinical Considerations in Vascular Homeostasis – Response to Pressure Decrease
- 52. The Cardiovascular System:Clinical Considerations in Vascular Homeostasis – Circulatory Shock • Circulatory Shock – system unable to maintain blood flow to supply oxygen, nutrients, etc. • Hypovolemic shock • Typically caused by hemorrhage, fluid loss • Tachycardia, weak pulse, rapid, shallow breathing • Cardiogenic shock • Inability of heart to maintain cardiac output • Arrhythmias, valve disorders, cardiomyopathies, cardiac failure • Vascular shock • Arterioles lose normal muscular tone or dilate dramatically • Sepsis • Neurogenic shock, Anaphylactic shock • Obstructive shock
- 53. The Cardiovascular System:Circulatory Pathways- Pulmonary
- 54. The Cardiovascular System:Circulatory Pathways – Systemic Arteries
- 55. The Cardiovascular System:Circulatory Pathways – Brain, Thoracic, Abdominal
- 56. The Cardiovascular System:Circulatory Pathways – Upper and Lower Limbs
- 57. The Cardiovascular System:Circulatory Pathways – Systemic Veins
- 58. The Cardiovascular System:Circulatory Pathways – Hepatic Portal Circulation
- 59. Hemangioblasts differentiate into angioblasts, whichgive rise to formed elements and blood islands. Angiogenesis – creation of new vessels from existing ones; follows nerve development The Cardiovascular System: Development and Fetal Circulation