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Ch 15: Blood Flow and the Control of Blood Pressure. Keypoints. Blood pressure (BP) and Regulation Exchange at capillaries Lymphatic system Cardio-vascular diseases. Fig 15-2. Angiogenesis. Growth of new blood vessels – occurs during Normal body maturation and growth - PowerPoint PPT Presentation
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Ch 15: Ch 15: Blood Flow and the Control Blood Flow and the Control
of Blood Pressure of Blood Pressure
1. Blood pressure (BP) and Regulation
2. Exchange at capillaries
3. Lymphatic system
4. Cardio-vascular diseases
Keypoints
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
Pressure created by ventricular contraction is driving force for blood flow
Pulsatile blood flow in arteries Elastic arteries expand and recoil for continuous blood flow
Pulse wave disappears past arterioles
Blood PressureBlood PressureFig 15-4
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
Auscultation of brachial artery with stethoscope in cubital fossa
Based on effects of
laminar flow vs.
turbulent flow
BP Estimated by SphygmomanometryBP Estimated by Sphygmomanometry
Principles ofPrinciples of SphygmomanometrySphygmomanometryCuff inflated until brachial artery compressed
and blood flow stopped kind of kind of sound?sound?
Compare to Fig 15-7
Pressures at which . . . . . . sound (= blood flow) first heard:
. . . sound disappeared:
CDAnimation
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 PressureMAP = Diastolic P + 1/3 Pulse Pressure (for 60 -80 bpm)
MAP for 120/80 = ?
MAP closer to diastolic pressure – why?
MAP influenced byMAP influenced by Cardiac output
Peripheral resistance (role of arterioles see Ch14) most common cause of hypertension
Total blood volume
Blood distributionFigs 15-8 & 10Figs 15-8 & 10
BP too low:BP too low:
Driving force for blood flow unable to overcome gravity
O2 supply to brain
Symptoms?
ShockShock= 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 perfusionSigns and symptoms?Management ?
BP too high:BP too high:
Weakening of arterial walls lead to Weakening of arterial walls lead to AneurysmsAneurysms Risk of rupture & Risk of rupture & hemorrhagehemorrhage
Cerebral hemorrhageCerebral hemorrhage
Rupture of major artery Rupture of major artery
Exchange at the CapillariesExchange at the Capillaries Capillaries are anatomically designed for
exchange
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
Fig 15-16
Methods of Capillary Exchange1. 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 15-18Fig 15-18
Close functional association with three other systems
1.
2.
3.
3) Lymphatic System3) Lymphatic System
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
EdemaEdemaDue to disruption of capillary exchangeDue 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)
Reflex control:Reflex control: Baroreceptor Reflex Baroreceptor Reflex = 1= 1o o
homeostatic control for BP homeostatic control for BP
Baroreceptors = stretch Baroreceptors = stretch sensitive ______receptors sensitive ______receptors in in aorta and carotid arteryaorta and carotid artery
Medullary CVCC integrates Medullary CVCC integrates neural neural controlcontrol
Regulation of Blood PressureRegulation of Blood Pressure
CDAnimation
Cardiovascular System: Blood Pressure Regulation Fig 15-22
Additional Control of BPAdditional Control of BP Arterial chemoreceptors activated by
O2
Cerebral cortex– emotional responses such as blushing &
fainting vasovagal response
Integration with Kidney function
Orthostatic hypotension normally triggers Baroreceptor reflex
Account for ~ 1/2 of deaths in US – most common: CAD or CHDCAD or CHD
Uncontrollable & controllable risk factors
Gender, age, genetics
Cigarette smoking, obesity, high BP, high cholesterol, DM
Cardiovascular Disease (CVD)Cardiovascular Disease (CVD)
Cigarette Smoking: Nicotinic cholinergic receptors stimulate Nicotinic cholinergic receptors stimulate
sympathetic neurons at ?sympathetic neurons at ?
Vasoconstriction & BP Vasoconstriction & BP
Risk for atherosclerosis Risk for atherosclerosis
Carbon monoxide Carbon monoxide (myocardium extracts most of (myocardium extracts most of OO22 brought to it under resting conditions) brought to it under resting conditions)
AtherosclerosisAtherosclerosisChanges in artery walls start with Changes in artery walls start with
lipid deposits lipid deposits
Macrophage ingests LDL-cholesterol Macrophage ingests LDL-cholesterol
Fatty streaks just under endothelial lining of Fatty streaks just under endothelial lining of larger arterieslarger arteries
MacrophageMacrophageparacrines attract smooth muscle paracrines attract smooth muscle cellscells
Smooth muscle cells proliferateSmooth muscle cells proliferate stable plaques vs. vulnerable plaquesstable plaques vs. vulnerable plaques
Cerebral and coronary thrombi and emboli Cerebral and coronary thrombi and emboli ? ?
Fig 15-24Fig 15-24
Role of Elevated Cholesterol in Role of Elevated Cholesterol in Development of AtherosclerosisDevelopment of Atherosclerosis
Lipids insoluble in plasma lipoproteins
Chylomicron to muscle & adipose cells, VLDL to adipose cells
2 main types of cholesterol carriers: HDL to liver vs. LDL to body cells
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