Wilson_BloodVessels&CircCh...pdf

1 Pages 719-747 C h a p t e r 21 Blood Vessels and Circulation Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Basic circulatory Route - Systemic Heart Arteries Arterioles Capillaries Tissues Venules Veins O2 Wastes 2 Vessel Structure ? Brief Comparison of Arteries and Veins ? Blood flows away from heart in ___________________ ? Blood flows toward heart in ______________________ ? Arteries are thicker than veins: ? Veins valves along their lengths ? Which vessels have the highest blood pressure? Vessel Structure ? Artery layers ? Tunica Externa ? Connective tissue ? Anchors vessel ? Tunica Media ? Smooth muscle ? External elastic membrane ? Tunica Intima ? Simple squamous endothelium ? Basement membrane ? Internal elastic membrane 3 Types of Arteries ? Elastic Arteries (>1cm) ? Larger arteries such as aorta ? Less muscle and more elastic tissue ? Why do larger arteries have more elastic tissue? ?Muscular Arteries (0.1mm ? 10mm) ? Medium size to smaller arteries ? More muscle, less elastic tissue ? Vasoconstrict and vasodilate to adjust blood flow Types of Arteries 4 Smaller Vessels ? Arterioles ? Smallest arteries (10-100 ?m) ? Deliver blood to capillaries ? Lose tunica externa ? Vasoconstrict and dilate to control blood flow to capillaries Types of Arteries Compared 5 Smaller Vessels ? Capillaries (4-10 ?m) ? Tubes of endothelium surrounded by basement membrane ? Function in exchange of substances with tissues ? Interconnect like a net to form capillary beds ? Three major types Smaller Vessels ? Venules (10?100 ?m) ? Small veins ? Collect blood from most capillaries ? Some smooth muscle ? Some exchange of substances with tissues 6 Capillaries and Associated Vessels Arteriole Capillaries Venule Metarteriole Thoroughfare Channel Arteriovenous Anastomosis Anastomoses ?Union of two or more vessels ? Types ? Arterial ? Venous ? Arteriovenous 7 Anastomoses ? Arterial anastomoses ? Ensures that arterial blockage does not totally interrupt circulation ? Examples are arteries of heart, brain and extremities ? Venous anastomoses ? Increase collection of blood from a structure ? Arteriovenous anastomoses ? Act as capillary bypasses as seen on previous slide Distribution of Blood ? Venous circulation has more blood than arterial circulation ? Veins are thin and can expand to accept more blood ? If needed, veins can constrict and push more blood into arteries. What might happen to require this? ? Pie chart shows how much blood is in different parts of circulation. 8 Blood Pressure ? Blood pressure (BP) is the force the blood exerts against vessel walls ? Difference in blood pressure (pressure gradient) along vessels causes blood to flow ? Blood flows from higher to lower pressure Blood Pressure ? Pressure is highest in the aorta and lowest in the vena cavae ? Though blood pressure is in every blood vessel, most of our discussion will concern arterial blood pressure ? The difference between pressure at the heart and pressure at peripheral capillary beds 9 Blood Pressure ? Basic formula for Blood Pressure ? Flow ? ?P ÷ R ? Flow is amount of blood flowing per minute and is equal to cardiac output (CO or Q) ? ?P means change or difference in pressure which causes blood to flow, and can be called just BP ? R stands for resistance to blood flow Blood Pressure ? Formula can be more simply written as: ? Flow ? BP ÷ R (Resistance) ? The above formula may be algebraically rearranged as follows: ? BP ? Flow X Resistance 10 Blood Pressure ? Two factors affect arterial blood pressure ? Blood flow ?Amount of blood moving through vessels per minute (cardiac output) ?What causes blood to flow? ?What can change blood flow? Blood Pressure ?Resistance to blood flow ?Blood encounters friction and turbulence ?Resistance is a force that acts against blood flow ?For blood to flow, blood pressure (BP) must be high enough to overcome the ______________________________ 11 Blood Pressure and Blood Flow ? Factors Affecting Blood Flow (cardiac output) ? Stroke volume ? Heart rate ? Changes in blood volume ? Total amount of blood in body (4-6 L) ? More than 10% drop causes drop in BP ? Flow and Blood Pressure ? Flow indicated by red ? Pressure indicated by blue Blood Pressure and Blood Flow 12 Blood Pressure and Resistance ? Factors Affecting Resistance ? Vessel diameter and resistance ? Vasoconstriction increases resistance ? Decreased blood flow to capillaries ? Increased arterial blood pressure Blood Pressure and Blood Flow ? Factors Affecting Resistance ? Vessel Diameter and Resistance ? Vasodilation decreases resistance ? Increased blood flow to capillaries ? Decreased arterial blood pressure? 13 Blood Pressure and Resistance ? Vasoconstriction and Resistance ? Black arrows indicate vasoconstriction ?arterial bp Vasoconstriction piBlood flow Blood Pressure and Resistance ? Vessel Length and Resistance ? Vascular resistance increases with vessel length ? What might cause increased vessel length? 14 Blood Pressure and Resistance ? Other Factors That Affect Resistance ? Viscosity ? Resistance caused by molecules and suspended materials in a liquid ? Whole blood viscosity is about five times that of water ? Does thicker blood increase or decrease resistance? Blood Pressure and Resistance ? Turbulence ? Swirling action that disturbs smooth flow of liquid ? Occurs in heart chambers and great vessels ? Atherosclerotic plaque causes abnormal turbulence 15 Blood Pressure ? Types of Pressures ? Blood pressure (BP or BHP ) ? Arterial pressure ? Pressure in arterial system ? Capillary hydrostatic pressure (CHP) ? Pressure within the capillary beds ? Venous pressure ? Pressure in the venous system Measurement of Arterial Blood Pressure ? BP measured in millimeters of mercury (mmHg) ? What device is used? ? Where is it most often taken? ? Two pressure ? Higher is _________________ pressure ? Produced by ___________________________ ? Lower is _________________ pressure ? Produced by ___________________________ 16 Measurement of Arterial Blood Pressure ? Pulse pressure ? Difference between systolic pressure and diastolic pressure ?Mean arterial pressure (MAP) ? MAP = diastolic pressure + 1/3 pulse pressure ? What is the clinical significance? Abnormal Arterial Blood Pressure ? Normal = 120/80* ? Hypertension ? Abnormally high blood pressure ? Systolic 140 or higher and diastolic 90 or higher ? Prehypertension ? Systolic of 120-130 and diastolic of 80-89 ? Left untreated may become hypertension ? Hypotension ? Abnormally low blood pressure ? Systolic of 90 or less and diastolic of 60 or less 17 Pressure and Blood Flow ? Elastic Rebound ? Arterial walls ? Stretch during systole ? Rebound (recoil to original shape) during diastole ? Keep blood moving during diastole Pressure and Blood Flow ? Pressures in Small Arteries and Arterioles ? Pressure and distance ? MAP and pulse pressure decrease with distance from heart ? Blood pressure decreases with friction ? Pulse pressure decreases due to elastic rebound 18 Pressure and Blood Flow Venous pressure and venous return ? Venous pressure is low ? Cannot return blood to heart by itself ? Venous return aided by: ? Venous valves ? Blood passes toward heart through successive one-way valves ? Compartmentalize blood to reduce pressure from gravity ? Contraction of skeletal muscles ? Muscles squeeze blood past successive valves ? Breathing ? Inhalation draws blood into the inferior vena cava ? Exhalation forces blood into right atrium 19 Blood Pressure and Veins Venous Valve ?Calf muscle squeezes vein ?Venous valve open ?Blood flows forward past valve ?Venous valve closed ?Blood cannot flow back down leg Which of the following is true? (A) Blood flows from lower to higher pressure (B) ? resistance causes pi arterial blood pressure (C) ? resistance causes ? arterial blood pressure (D) ? blood flow causes pi arterial blood pressure Question 20 The low number of a blood pressure reading occurs when the _______________. (A) ventricle is pumping (B) ventricle is relaxing (C) AV valves are closed (D) SLvalves are open Question Capillary Exchange ? Vital to homeostasis ? Moves materials between capillaries and interstitial Fluid (IF) by: ? Diffusion ? Filtration ? Reabsorption 21 Capillary Exchange ? Diffusion ? Movement of ions or molecules ? From high concentration ? To lower concentration ? Down the concentration gradient Capillary Exchange ? Filtration ? Driven by blood hydrostatic pressure ? Water and small solutes forced through capillary wall ? Leaves larger solutes in bloodstream 22 Capillary Exchange ? Reabsorption ? Driven by osmosis ? Blood osmotic pressure (BOP) ? Pressure that draws water into blood ? Caused by plasma proteins (especially albumins) too large to cross capillary walls ? Why is it called blood colloidal osmotic pressure? Capillary Exchange ? Opposing pressures ? Capillary hydrostatic pressure (CHP) forces water and solute out of capillaries ? Blood osmotic pressure (BOP) draws water and solute into capillaries CHP BOP CHP pushes fluid out to IF BOP pulls fluid into blood Interstitial Fluid (IF) 23 Capillary Exchange ? Mechanism of Filtration and Reabsorption ? On arteriole side of capillary, CHP ! BOP, so push ! pull ? On venule side of capillary, BOP ! CHP, so pull ! push CHP BOP CHP BOP Filtration into interstitial fluid Push Pull Push Pull Reabsorption into blood Capillary Exchange Diagram BOP (pull) 25 mmHg CHP (push) (18 mmHg) BOP (pull) (25 mmHg) Filtration CHP (push) (35 mmHg) Reabsorption Blood Capillary Lymph Capillary Interstitial Fluid Interstitial Fluid Arteriole End Venule End 24 Summary of Capillary Filtration and Reabsorption ? At arterial end of capillary ? Fluid moves out of capillary into interstitial fluid ? At venous end of capillary ? Fluid moves into capillary from interstitial fluid ? Capillaries filter more than they reabsorb ? Excess fluid enters lymphatic vessels Which of the following causes capillary filtration? 1 BOP>CHP *2 CHP>BOP 3 CHP=BOP 4 vasoconstriction Question 25 Cardiovascular Regulation ? Controlling Cardiac Output and Blood Pressure ? Autoregulation ? Causes immediate, localized homeostatic adjustments ? Neural mechanisms ? Respond quickly to changes at specific sites ? Endocrine mechanisms ? Direct longer-term changes Cardiovascular Regulation ? Autoregulation ? Local regulation within tissues ? Assures proper blood flow into capillaries ? Tissues regulate blood flow to meet their needs ? Changes in blood pressure, blood chemistry, and blood temperature cause ? increased capillary blood flow by _________________________________________ or ? decreased capillary blood flow by _________________________________________ 26 Cardiovascular Regulation ? Neural Mechanism ? Motor (output) to heart and blood vessels ? Cardiovascular Centers (CV) of the medulla oblongata ? Cardiac Centers ? CAC increases HR and cardiac output ? CIC decreases HR and cardiac output ? Vasomotor Centers ? Decrease blood flow to most organs by causing widespread _________________________________ ? What effect does widespread vasoconstriction have on arterial blood pressure? Cardiovascular Regulation ? Sensory Adjustments in Cardiac Output and vasomotor regulation ? For cardiovascular centers of medulla oblongata to make proper adjustments, must be input from different sensory receptors ? __________________ sense changes in blood pressure ? _________________ sense changes in certain blood chemicals 27 Cardiovascular Regulation = Sensory input = Motor output Cardiovascular Regulation ? Reflex Control of Cardiovascular Function ? Cardiovascular centers monitor arterial blood ? Baroreceptor reflexes: ? respond to changes in blood pressure ? control bp to brain and entire body ? Chemoreceptor reflexes: ? respond to changes in chemical composition, particularly pH and dissolved gases (CO2 and O2) ? Affect heart rate and respiration 28 ? Baroreceptor Reflexes ? Baroreceptors in walls of blood vessels and heart ? Aortic/Carotid (left heart) reflex ? Carotid sinuses: monitor bp to brain ? Aortic sinuses: monitor bp in systemic circuit ? Atrial (right heart) reflex ? Baroreceptors in right atrium and vena cavae monitor venous pressure (pressure of systemic blood returning to heart) Carotid Sinus Baroreceptors Cardiovascular Regulation Aortic Baroreceptors Cardiovascular Regulation ? Aortic/Carotid (Left Heart) Reflex ? If bp rises, baroreceptors stimulated ? Reflex decrease in heart rate ? Reflex vasodilation ? What does this cause? ? If bp falls, baroreceptors inhibited ? Reflex increase in heart rate ? Reflex vasoconstriction ? What does this cause? 29 Aortic/carotid Reflex Figure 21?14 Baroreceptor Reflexes of the Carotid and Aortic Sinuses Atrial (Right Heart) Reflex ? Baroreceptors in the vena cavae and right atrium ? ?Venous return causes ? ?blood pressure in vena cavae and right atrium ? Results in increased baroreceptor stimulation ? Results in temporary increase in cardiac output ? Sort of the opposite of the left heart reflex 30 Cardiovascular Regulation ? Chemoreceptor Reflexes ? Respond to changes in CO2, O2 and pH ? Peripheral chemoreceptors in carotid bodies and aortic bodies monitor blood gases and pH ? Central chemoreceptors below medulla oblongata ? Monitor cerebrospinal fluid ? Control respiratory function ? Control blood flow to brain Cardiovascular Regulation Figure 21?15 The Chemoreceptor Reflexes 31 What occurs when blood pressure increases? (A) pi baroreceptor stimulation ? heart rate, and vasoconstriction (B) pi baroreceptor stimulation pi heart rate, and vasoconstriction (C) ? baroreceptor stimulation pi heart rate, and vasodilation (D) ?baroreceptor stimulation ? heart rate, and vasodilation Question Cardiovascular Regulation ? Hormones and Cardiovascular Regulation ? Hormones can have short-term and long-term effects on cardiovascular regulation ? For example, epinephrine (EPI) and norepinephrine (NE) from adrenal gland can quickly stimulate cardiac output and peripheral vasoconstriction ? This results in ___________________ bp 32 Cardiovascular Regulation ? Longer Term Hormonal Regulation ? Antidiuretic Hormone (ADH aka Vasopressin) ? Released by pituitary gland in response to reduced intake or loss of water ? Reduces water loss by kidneys or increases blood volume ? Stimulates widespread vasoconstriction (vasopressin) or increases peripheral resistance Cardiovascular Regulation ? ADH responds to ? Decreased blood volume ? Increased plasma osmotic pressure ? Circulating hormone called angiotensin II 33 Cardiovascular Regulation ? Longer Term Hormonal Regulation ? Angiotensin II ? Produced in response to a fall in renal blood pressure ? Stimulates ? ADH secretion (remember what is does) ? Aldosterone production (What does it cause?) ? Thirst ? Increased cardiac output (CO) ? Peripheral vasoconstriction Cardiovascular Regulation ? Angiotensin formation: ? Aldosterone secretion by adrenal glands salt retention ? ADH secretion water retention ? ? Thirst water intake ? ? Water and salt ? cardiac output (CO) ? ? peripheral vasoconstriction ? peripheral resistance ? ? CO and peripheral resistance ? blood pressure Angiotensinogen Angiotensin I Angiotensin II ACE Renin from Kidneys 34 Cardiovascular Regulation ? Erythropoietin (EPO) ? Released by kidneys ? In response to low blood pressure, low O2 content in blood ? Stimulates red blood cell production ? This results in _________________________ _____________________________________ Cardiovascular Regulation Figure 21?16a The Hormonal Regulation of Blood Pressure and Blood Volume. 35 Which of the following maintains adequate blood pressure to the brain when a person stands up? (A) ?stimulation of carotid baroreceptors with reflex slowing of the heart and vasodilation (B) ?stimulation of carotid baroreceptors with reflex slowing of the heart and vasoconstriction (C) pistimulation of carotid baroreceptors with reflex speeding-up of the heart and vasoconstriction (D) pistimulation of carotid baroreceptors with reflex slowing of the heart and vasodilation Question Medical Terms ? Hypertension ? Aneurysm ? Stroke (CVA or brain attack ? Claudication 36 ? Deep Venous Thrombosis ? Phlebitis ? Phlebotomist ? Venipuncture Clinical Terms binstructor Basic circulatory route