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Ch 15: Blood Flow and the Control of Blood Pressure Keypoints 1. Blood pressure (BP) and Regulation 2. Exchange at capillaries 3. Lymphatic system 4. Cardio-vascular diseases Fig 15-2 Angiogenesis Growth of new blood vessels – occurs during – Normal body maturation and growth – Monthly re-growth of functional endometrium – Wound healing – Endurance training – Cancer growth Clinical implications: Promote or inhibit angiogenesis with relevant cytokines Blood Pressure Pressure created by ventricular contraction is driving force for blood flow Fig 15-4 Pulsatile blood flow in arteries Elastic arteries expand and recoil for continuous blood flow Pulse wave disappears past arterioles Blood Pressure (BP) Measurements Ventricular pressure difficult to measure measure arterial BP BP highest in the arteries – falls continuously throughout systemic circulation Read as “Systolic over diastolic”– normal value 120 / 80 mm Hg 2003: New range for blood pressure readings between 120/80 and 139/89 “Prehypertension” Diastolic pressure in ventricle: ? mm Hg BP Estimated by Sphygmomanometry Auscultation of brachial artery with stethoscope in cubital fossa Based on effects of laminar flow vs. turbulent flow Principles of Sphygmomanometry Cuff inflated until brachial artery compressed and blood flow stopped kind of sound? Compare to Fig 15-7 Slowly release pressure in cuff: turbulent flow Pressures at which . . . . . . sound (= blood flow) first heard: . . . sound disappeared: CD Animation Cardiovascular System: Measuring Blood Pressure Mean Arterial Pressure Sometimes useful to have single value for driving pressure: Mean Arterial Pressure MAP = Diastolic P + 1/3 Pulse Pressure (for 60 -80 bpm) MAP for 120/80 = ? MAP closer to diastolic pressure – why? MAP influenced by Cardiac output Peripheral resistance (role of arterioles see Ch14) most common cause of hypertension Total blood volume Blood distribution Figs 15-8 & 10 BP too low: Driving force for blood flow unable to overcome gravity O2 supply to brain Symptoms? Shock = generalized circulatory failure Hypovolemic shock volume loss (dehydration, blood loss, burns) Distributive shock loss of vascular tone (anaphylactic, septic, toxic) Cardiogenic shock pump failure Dissociative shock inability of RBC to deliver O2 (CO poisoning) Cell damage due to inadequate perfusion Signs and symptoms? Management ? BP too high: Weakening of arterial walls lead to Aneurysms Risk of rupture & hemorrhage Cerebral Rupture hemorrhage of major artery Exchange at the Capillaries Capillaries are anatomically designed for exchange Fig 15-16 Capillary blood flow: Greatest total cross sectional area Velocity ? Most cells within ____ µm of capillary – why? Direct correlation between # of caps and metabolic needs of tissue Three types of exchange of molecules across the barrier Methods of Capillary Exchange 1. Paracellular diffusion 2. Transendothelial transport (transcytosis) – some diffusion 3. Bulk flow: mass movement of H2O and dissolved solutes as result of hydrostatic or osmotic pressure Filtration – flow direction out of caps Absorption – flow direction into caps Two Forces Regulate Capillary Bulk Flow Hydrostatic P: lateral component of fluid flow Osmotic P: due to solute difference (main solute difference due to?) Mostly: Net filtration at arterial end Net re-absorption at venous end Fig 15-18 Fluid Exchange = Pcap + cap cap = 25 mmHg Fig 15-18 3) Lymphatic System Close functional association with three other systems 1. 2. 3. Lymphatic System Functions Return filtered fluid & proteins to circulatory system (anatomical design!) – Fig 15-18 Transfer fat from small intestine to circulatory system Trap and deal with pathogens Edema Due to disruption of capillary exchange 2 major causes: 1. Blockage of lymph drainage – Cancer & fibrotic growth – Pathogens 2. Capillary filtration > absorption – Venous pressure due to right / left heart failure – Plasma protein concentration due to liver failure or severe malnutrition (Kwashiorkor) Right or Left Heart Failure? Alveolar Flooding Sweden Kroniskt invalidiserande lymfödem (2,1 liter) i höger arm sedan 8 år. Kwashiorkor Regulation of Blood Pressure Reflex control: Baroreceptor Reflex = 1o homeostatic control for BP Baroreceptors = stretch sensitive ______receptors in aorta and carotid artery Medullary CVCC integrates neural control Cardiovascular System: CD Animation Blood Pressure Regulation Fig 15-22 Additional Control of BP Arterial chemoreceptors activated by O 2 Cerebral cortex – emotional responses such as blushing & fainting vasovagal response Integration with Kidney function Orthostatic hypotension normally triggers Baroreceptor reflex Cardiovascular Disease (CVD) Account for ~ 1/2 of deaths in US – most common: CAD or CHD Uncontrollable & controllable risk factors Gender, age, genetics Cigarette smoking, obesity, high BP, high cholesterol, DM Cigarette Smoking: Nicotinic cholinergic receptors stimulate sympathetic neurons at ? Vasoconstriction Risk & BP for atherosclerosis Carbon monoxide (myocardium extracts most of O2 brought to it under resting conditions) Atherosclerosis Changes in artery walls start with lipid deposits Macrophage ingests LDL-cholesterol Fatty streaks just under endothelial lining of larger arteries Macrophage paracrines attract smooth muscle cells Fig 15-24 Smooth muscle cells proliferate stable plaques vs. vulnerable plaques Cerebral and coronary thrombi and emboli ? Role of Elevated Cholesterol in Development of Atherosclerosis Lipids insoluble in plasma lipoproteins Chylomicron , VLDL to adipose to muscle & adipose cells cells 2 main types of cholesterol carriers: HDL to liver vs. LDL to body cells Essential Hypertension the end