Chapter 4 Vasculature PDF

Figure 19.4 Anatomy of a capillary bed. Vascular shunt sphincterering Of Precapillary Exam...

Figure 19.4 Anatomy of a capillary bed. Vascular shunt sphincterering Of Precapillary Exam 0 sphincters Metarteriole Thoroughfare that starts here channel muscle can open up close of when fn is what it 000 wouldlook like neededfa open close True capillaries if it were not outside OFF Terminal arteriole Postcapillary venule sphincters Sphincters open—blood flows through true capillaries. localizedblood flow control ex when it's cold outside Terminal arteriole Postcapillary venule Sphincters closed—blood flows through metarteriole – © 2016 Pearson Education, Inc. thoroughfare channel and bypasses true capillaries. Bio 202 A&P ASU DPC T. Penkrot  Veins thinner walls  Formed when venules converge  Have all tunics, but thinner walls with large lumens compared with corresponding arteries  Tunica media is thin, but tunica externa is thick Contain collagen fibers and elastic networks  Large lumen and thin walls make veins good storage vessels Called capacitance vessels (blood reservoirs) because they contain up to 65% of blood supply than their veins are usually larger corresponding arteries in cadavers you it seedried blood in veins © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot you really won't see blood  Figure 19.5 Relative proportion of blood volume throughout the cardiovascular system. Pulmonary blood vessels 12% Systemic arteries and arterioles 15% Heart 8% Capillaries 5% Systemic veins and venules 60% © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 19.2a Generalized structure of arteries, veins, and capillaries. Artery Vein © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot Part 2 Physiology of Circulation 19.6 Flow, Pressure, and Resistance Definition of Terms  Blood flow: volume of blood flowing through vessel, organ, or entire circulation in given period Measured in ml/min, it is equivalent to cardiac output (CO) for entire vascular system Overall is relatively constant when at rest, but at any given moment, varies at individual organ level, based on needs © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Definition of Terms (cont.)  Blood pressure (BP): force per unit area exerted on wall of blood vessel by blood Expressed in mm Hg Measured as systemic arterial BP in large arteries near heart Aida Pressure gradient provides driving force that keeps blood moving from higher- to lower-pressure areas ensures oxygenation © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Definition of Terms (cont.) if oh f8net sistancein  Resistance (peripheral resistance): opposition to flow Measurement of amount of friction blood encounters with vessel walls, generally in peripheral (systemic) circulation Three important sources of resistance ― Blood viscosity bloodthickness h hge hatmuon ― Total blood vessel length distancefromthe heart rommin ― *Blood vessel diameter* minff  R is more important in influencing local blood flow because it is easily changed by altering blood vessel Gm diameter vasoconstrictionvasodilation change vesseldiameter quickly easily © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 19.6 Blood pressure in various blood vessels of the systemic circulation. w changes dramatically 120 EEEEaaetforffeveryneartbe.at Blood pressure (mm Hg) highestBP becauseit Systolic pressure big 100 Intracti Mean pressure pinkcaverageBP 80 Jedropin BPin arterioles T.FI 60 Ihi hh Diastolic drops the most w 40 pressure arteriors 20 ventricles in 0 diastone iffi i heart © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Arterial Blood Pressure (cont.)  Systolic pressure: pressure exerted in aorta during ventricular contraction Left ventricle pumps blood into aorta, imparting kinetic energy that stretches aorta Averages 120 mm Hg in normal adult  Diastolic pressure: lowest level of aortic pressure when heart is at rest d  Pulse pressure: difference between systolic and diastolic pressure Systolic BP Diastolic BP 120 80 40putspressure  Pulse: throbbing of arteries due to difference in pulse pressures, which can be felt under skin © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Arterial Blood Pressure (cont.)  Mean arterial pressure (MAP): pressure that propels blood to tissues  MAP is calculated by adding diastolic pressure  1/3 pulse pressure Example: BP  120/80; Pulse Pressure  120 − 80  40; so MAP 80  (1/3)40 80  13  93 mm Hg  Pulse pressure and MAP both decline with increasing distance from heart © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot Figure 19.7 Body sites where the pulse is most easily palpated. Superficial temporal artery Facial artery Common carotid artery Brachial artery Radial artery Femoral artery Popliteal artery Posterior tibial artery Dorsalis pedis artery © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Venous Blood Pressure (cont.)  Factors aiding venous return 1. Muscular pump: contraction of skeletal muscles helps squeeze blood back toward heart; valves prevent backflow 2. Respiratory pump: pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand 3. Sympathetic venoconstriction: under sympathetic control, smooth muscles constrict, pushing blood back toward heart © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot Figure 19.8 The muscular pump. Venous valve (open) Contracted skeletal muscle Venous valve (closed) Vein Direction of blood flow © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  19.8 Regulation of Blood Pressure  Maintaining blood pressure requires cooperation of heart, blood vessels, and kidneys All supervised by brain  Three main factors regulating blood pressure Cardiac output (CO) Peripheral resistance (PR) Blood volume © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 19.9 Major factors determining MAP. Stroke Heart Diameter of Blood Blood volume rate blood vessels viscosity vessel length Cardiac output Peripheral resistance Mean arterial pressure (MAP) © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 19.11 Direct and indirect Indirect Direct renal mechanism (hormonal) mechanisms for renal control of blood renal mechanism (renin-angiotensin-aldosterone) pressure. Initial stimulus Arterial pressure Arterial pressure Physiological response Result Inhibits baroreceptors Sympathetic nervous system activity Filtration by kidneys Angiotensinogen Renin release from kidneys Angiotensin I Angiotensin converting enzyme (ACE) Angiotensin II Urine formation ADH release by Thirst via Vasoconstriction; Adrenal cortex posterior pituitary hypothalamus peripheral resistance Secretes Aldosterone Blood volume Sodium reabsorption Water reabsorption Water intake by kidneys by kidneys Blood volume Mean arterial pressure Mean arterial pressure © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 19.12 Factors that increase MAP. Activity of Release Fluid loss from Crisis stressors: Vasomotor tone; Dehydration, Body size muscular of ANPP hemorrhage, exercise, trauma, bloodborne high hematocrit pump and excessive body chemicals respiratory sweating temperature (epinephrine, pump NE, ADH, angiotensin II) Conservation Blood volume Blood pH of Na and Blood pressure O2 water by kidneys CO2 Blood Baroreceptors Chemoreceptors volume Venous Activation of vasomotor and cardio- return acceleratory centers in brain stem Diameter of Blood Blood vessel Stroke Heart blood vessels viscosity length volume rate Cardiac output Peripheral resistance Initial stimulus Physiological response Mean arterial pressure (MAP) Result © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Homeostatic Imbalances in Blood Pressure  Hypertension Sustained elevated arterial pressure of 140/90 mm Hg or higher Prehypertension if values elevated but not yet in hypertension range ― May be transient adaptations during fever, physical exertion, and emotional upset ― Often persistent in obese people Prolonged hypertension is major cause of heart failure, vascular disease, renal failure, and stroke ― Heart must work harder; myocardium enlarges, weakens, and becomes flabby ― Also accelerates atherosclerosis © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot Homeostatic Imbalances in Blood Pressure (cont.)  Circulatory shock Condition where blood vessels inadequately fill and cannot circulate blood normally ― Inadequate blood flow cannot meet tissue needs Hypovolemic shock results from large-scale blood loss Vascular shock results from extreme vasodilation and decreased peripheral resistance Cardiogenic shock results when an inefficient heart cannot sustain adequate circulation © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 19.13 Distribution of blood flow at rest and during strenuous exercise. 750 750 Brain 750 12,500 Heart 250 Skeletal 1200 muscles Skin 500 Kidneys 1100 Abdomen 1400 1900 Other 600 Total blood 600 flow at rest 5800 ml/min 600 400 Total blood flow during strenuous exercise © 2016 Pearson Education, Inc. 17,500 ml/min Bio 202 A&P ASU DPC T. Penkrot  Autoregulation: Intrinsic (Local) Regulation of Blood Flow  Autoregulation: local (intrinsic) conditions that regulate blood flow to that area Reactive hyperemia: increased blood flow to an area due to intrinsic factors  Two types of intrinsic mechanisms both determine final autoregulatory response Metabolic controls Myogenic controls © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot Autoregulation: Intrinsic (Local) Regulation of Blood Flow (cont.)  Long-term autoregulation Occurs when short-term autoregulation cannot meet tissue nutrient requirements ― Long-term autoregulation may take weeks or months to increase blood supply Number of vessels to region increases (angiogenesis), and existing vessels enlarge Common in heart when coronary vessel occluded, or throughout body in people in high-altitude areas © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 19.14 Intrinsic and extrinsic control of arteriolar smooth muscle in the Vasodilators systemic circulation. Metabolic Neural O2 Sympathetic tone CO2 H Hormonal K Atrial natriuretic Prostaglandins peptide Adenosine Nitric oxide Extrinsic controls Intrinsic controls (autoregulation) Vasoconstrictors Neural or hormonal controls Maintain mean arterial pressure Metabolic or myogenic controls (MAP) Distribute blood flow to individual Redistribute blood during exercise organs and tissues as needed and thermoregulation Myogenic Neural Stretch Sympathetic tone Metabolic Hormonal Endothelins Angiotensin II Antidiuretic hormone Epinephrine Norepinephrine © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot Figure 19.15 Active hyperemia. Exercising skeletal muscle O2, CO2, H, and other metabolic factors in extracellular fluid Vasodilation of arterioles (overrides extrinsic sympathetic input) Initial stimulus Muscle blood Physiological flow (active response hyperemia) Result © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 19.16 Blood flow velocity and total cross-sectional area of vessels. Relative cross- sectional area of different vessels of the vascular bed 5000 Total area 4000 (cm2) of the 3000 vascular 2000 bed 1000 0 50 40 Velocity of 30 blood flow (cm/s) 20 10 0 © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Figure 19.17-2 Capillary transport mechanisms. Lumen Caveolae Pinocytotic vesicles Endothelial fenestration Intercellular (pore) cleft 4 Transport via vesicles or caveolae (large substances) Basement 3 Movement membrane through fenestrations 2 Movement (water-soluble 1 Diffusion through substances) through intercellular clefts membrane (water-soluble (lipid-soluble substances) substances) © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Focus Figure 19.1-1 Bulk fluid flow across capillary walls causes continuous mixing of fluid between the plasma and the interstitial fluid compartments, and maintains the interstitial environment. The big picture Arteriole Each day, 20 L of fluid filters from capillaries at their arteriolar end and flows through the interstitial space. Most (17 L) is reabsorbed at the venous end. Fluid moves through the interstitial space. For all capillary beds, 20 L of fluid is filtered out per day—almost 7 times the total plasma volume! 17 L of fluid per day is reabsorbed into the capillaries at the venous end. About 3 L per day of fluid (and any leaked proteins) are removed by the lymphatic Venule system (see Chapter 20). Lymphatic capillary © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Focus Figure 19.1-3 Bulk fluid flow across capillary walls causes continuous mixing of fluid between the plasma and the interstitial fluid compartments, and maintains the interstitial environment. How do the pressures drive fluid flow across a capillary? Net filtration occurs at the arteriolar end of a capillary. Capillary lumen Boundary Interstitial fluid (capillary wall) Hydrostatic pressure in capillary (HPc) “pushes” fluid out of capillary. HPc  35 mm Hg Osmotic pressure in capillary OPc  26 mm Hg (OPc) “pulls” fluid into capillary. Let’s use what we know about pressures to determine the net filtration pressure (NFP) at any point. (NFP is the pressure Hydrostatic pressure driving fluid out of the capillary.) To do HPif  0 mm Hg (HPif) in interstitial fluid this we calculate the outward pressures “pushes” fluid into (HPc and OPif) minus the inward capillary. pressures (HPif and OPc). So, OPif  1 mm Hg Osmotic pressure (OPif) NFP  (HPc  OPif)  (HPif  OPc) in interstitial fluid “pulls” fluid out of capillary.  (35  1)  (0  26)  10 mm Hg (net outward pressure) As a result, fluid moves from the NFP  10 mm Hg capillary into the interstitial space. © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot  Focus Figure 19.1-4 Bulk fluid flow across capillary walls causes continuous mixing of fluid between the plasma and the interstitial fluid compartments, and maintains the interstitial environment. Net reabsorption occurs at the venous end of a capillary. Capillary lumen Boundary Interstitial fluid (capillary wall) Hydrostatic pressure in capillary “pushes” fluid out of capillary. HPc  17 mm Hg The pressure has dropped because of resistance encountered along the capillaries. Osmotic pressure in capillary OPc  26 mm Hg “pulls” fluid into capillary. Again, we calculate the NFP: HPif  0 mm Hg Hydrostatic pressure in interstitial fluid “pushes” fluid into capillary. NFP  (HPc  OPif)  (HPif  OPc)  (17  1)  (0  26)  8 mm Hg (net inward pressure) OPif  1 mm Hg Osmotic pressure in interstitial fluid “pulls” fluid out of capillary. Notice that the NFP at the venous end is a negative number. This means that reabsorption, not filtration, is occurring and so fluid moves from the NFP 8 mm Hg interstitial space into the capillary. © 2016 Pearson Education, Inc. Bio 202 A&P ASU DPC T. Penkrot