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Chapter 15

Chapter 15. Blood Flow and the Control of Blood Pressure. About this Chapter. How various blood vessels are constructed and role in circulation Components of "blood pressure", role and measurement Product exchange at the capillary beds Lymph vessels, distribution and role in circulation

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Chapter 15

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  1. Chapter 15 Blood Flow and the Control of Blood Pressure

  2. About this Chapter • How various blood vessels are constructed and role in circulation • Components of "blood pressure", role and measurement • Product exchange at the capillary beds • Lymph vessels, distribution and role in circulation • How blood pressure and circulation are regulated • Key components of cardiovascular disease

  3. The Blood Vessels and the Cardiovascular System • Arteries: blood from heart • Strong & Elastic • Conduct blood to capillaries • Sphincters • Capillaries: exchange with cells • Veins • Return blood to heart • Valves

  4. The Blood Vessels and the Cardiovascular System Figure 15-1: Functional model of the cardiovascular system

  5. Make Up of Blood Vessels: Arteries and Arterioles • Endothelium • Elastic tissues • Rebounds • Evens flow • Smooth muscles • Fibrous tissue • Tough • Resists stretch Figure 15-2: Blood vessels

  6. Make Up of Blood Vessels: Capillaries • Endothelium: one cell thick • Continuous • Fenestrated • Basement membrane

  7. Make Up of Blood Vessels: Capillaries Figure 15-16: Types of capillaries

  8. Make Up of Blood Vessels:Veins and Venules (Contrasted to Arteries) • Thinner walls • Larger diameter • Closer to skin • Less muscle • Less elastic Figure 15-3: Metarterioles

  9. Angiogenesis: Growth of New Blood Vessels • Normal body maturation and growth • Endometrium • Endurance training • Abnormal growth to service cancerous tissue • Wound repair and consequences • Failure to regrow in heart tissues after heart attack • Failure to regrow in brain after stroke

  10. Blood Pressure: Generated by Ventricular Contraction • Pulsatile: surges in arteries • Elastic rebound evens & maintains pressure

  11. Blood Pressure: Generated by Ventricular Contraction Figure 15-4: Elastic recoil in the arteries

  12. Blood Pressure (BP): Measurements • "Blood pressure" • Systolic over diastolic • About 120/80 mmHg • Sphygmomanometer • "Estimate of pressure" • Korotkoff sounds

  13. Blood Pressure (BP): Measurements Figure 15-7: Measurement of arterial blood pressure

  14. More Blood Pressures: Pulse and Mean Arterial Pressures • Pulse pressure = Systolic–Diastolic • Mean arterial pressure (MAP) = Diastolic + 1/3 pulse pressure

  15. More Blood Pressures: Pulse and Mean Arterial Pressures Figure 15-5: Pressure throughout the systemic circulation

  16. Factors Controlling MAP : The Driving Pressure for Blood Flow • Blood volume • Cardiac output • Resistance • Distribution

  17. Factors Controlling MAP : The Driving Pressure for Blood Flow Figure 15-10: Factors that influence mean arterial pressure

  18. Antihypertensive Drug Classes: Action Sites  CardiacOutput Total Peripheral Resistance Blood Pressure = -Blockers ACE Inhibitors AT1 Blockers Direct renin inhibitors 1-Blockers 2-Agonists All CCBs Diuretics Sympatholytics Vasodilators -Blockers Non-DHP CCBs Diuretics Antihypertensive Drug Classes ACE = angiotensin-converting enzyme; AT1 = angiotensin type 1; CCBs = calcium channel blockers; DHP = dihydropyridine

  19. Classes of Antihypertensive Drugs Aldosterone receptor antagonists (blockers) Angiotensin II antagonists Angiotensin-converting enzyme inhibitors -Blockers 1-Selective Nonselective -Blockers -1/-2 -1 predominant / Intrinsic sympathomimetic activity Calcium channel antagonists Nondihydropyridine Dihydropyridine Central 2 agonists Direct renin inhibitors Direct vasodilators Diuretics Thiazide-type Loop-type Potassium-sparing Ganglionic blockers

  20. Arteriole Resistance: Control of Local Blood Flow • Myogenic auto regulation • Paracrines: • Hyperemia • Sympathetic nerves – CNS

  21. Distribution of Blood in the Body Organs Figure 15-13: Distribution of blood in the body at rest

  22. Capillary Blood Flow: Greatest Total Cross Sectional Area • Lowest Velocity • Hydrostatic pressure drops Figure 15-17: The velocity of flow depends on the total cross-sectional area

  23. Capillary Exchange: Colloidal Osmotic Pressure is Constant • Proteins stay in capillary • Water, oxygen, glucose – move out • CO2, N wastes, water – move in • Bulk flow out on arterial side, in on venous side

  24. Capillary Exchange: Hydrostatic Pressure Declines • High on arterial side – bulk flow out • Low on venous side – bulk flow in • Fenestrations &/or leaky joints speed exchange Figure 15-18a: Fluid exchange at the capillary

  25. Net Out Flow Into ECF • Net filtration – net absorption = net out flow • About 2 L/day collected by lymph vessels Figure 15-18b: Fluid exchange at the capillary

  26. Lymphatic System: Structure and Roles (overview) • Lymphatic structures • Capillaries with valves • Lymph vessels • Lymph nodes & organs • Immune defense: lymphocytes • Transport of fats • Collects excess ECF • Returns to plasma • Edema

  27. Lymphatic System: Structure and Roles (overview) Figure 15-19: The lymphatic system

  28. Lymphatic System: Overview • Consists of two semi-independent parts • A meandering network of lymphatic vessels • Lymphoid tissues and organs scattered throughout the body • Returns interstitial fluid and leaked plasma proteins back to the blood • Lymph – interstitial fluid once it has entered lymphatic vessels

  29. Figure 20.2a

  30. Lymphatic System: Overview Figure 20.1a

  31. Lymphatic Capillaries • Similar to blood capillaries, with modifications • Remarkably permeable • Loosely joined endothelial minivalves • Withstand interstitial pressure and remain open • The minivalves function as one-way gates that: • Allow interstitial fluid to enter lymph capillaries • Do not allow lymph to escape from the capillaries

  32. Lymphatic Capillaries • During inflammation, lymph capillaries can absorb: • Cell debris • Pathogens • Cancer cells • Cells in the lymph nodes: • Cleanse and “examine” this debris • Lacteals – specialized lymph capillaries present in intestinal mucosa • Absorb digested fat and deliver chyle to the blood

  33. Lymphatic Trunks • Lymph is delivered into one of two large trunks • Right lymphatic duct – drains the right upper arm and the right side of the head and thorax • Thoracic duct – arises from the cisterna chyli and drains the rest of the body

  34. Lymph Transport • The lymphatic system lacks an organ that acts as a pump • Vessels are low-pressure conduits • Uses the same methods as veins to propel lymph • Pulsations of nearby arteries • Contractions of smooth muscle in the walls of the lymphatics

  35. Regulation of Blood Pressure and Heart Rate • Medullary cardiac control center (Brainstem) • Cardioacceleratory Center • Cardioinhibitory Center • Baroreceptor reflex • Carotid • Aortic • Kidney: blood volume • Hypothalamus & Cortex: stress, blushing, etc.

  36. Regulation of Blood Pressure Figure 15-22: The baroreceptor reflex: the response to increased blood pressure

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