Cardiovascular (Blood Vessel) - PDF

Anatomy and Physiology, 1e Chapter 20: The Cardiovascular System: Blood Vessels and...

Anatomy and Physiology, 1e Chapter 20: The Cardiovascular System: Blood Vessels and Circulation Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 1 posted to a publicly accessible website, in whole or in part. Icebreaker In the previous chapters, we discussed blood and how the heart helps to generate movement of blood. As blood moves, it flows through blood vessels. Are all blood vessels the same? Do the vessels influence how blood moves? What makes blood flow through the vessels? In this chapter we will discuss blood vessels and how they allow for the movement of blood.  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 2 Anatomy of Blood Vessels Section 20.1 Learning Objectives 20.1.1–20.1.8 Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 3 posted to a publicly accessible website, in whole or in part.  Review of Topics Related to Blood Flow (Figure 20.1) Blood moves through the body by bulk flow through blood vessels Flow is proportional to a pressure gradient that must overcome resistance High pressure flows to low pressure Arteries carry blood away from the heart and branch to form other vessels Capillary exchange with tissues occurs primarily via diffusion posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or  publicly accessible website, in whole or in part. 4 Circulation Pathways (Figure 20.2) Systemic circuit carries blood throughout body to supply oxygen and nutrients to tissues Pulmonary circuit carries blood to the lung for gas exchange Arteries carry blood away from heart Branch to form arterioles Capillaries are the sites of exchange Venules and veins carry blood back toward heart  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 5 Histology of Arteries and Veins (Figure 20.3) Blood vessels share same general characteristics Vary slightly in structure Lumen = hollow space blood flows through Arteries and arterioles smaller lumen and thicker walls To withstand higher pressures Veins and venules have thinner walls and larger lumen  Exposed to lower pressures Veins contain valves to ensure one-way flow posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 6 Anatomy of Blood Vessel Walls (Figure 20.4) Blood travels throughout body in blood vessels Travels from areas of higher to lower pressure Blood vessel walls are made of layers called tunics  1. Tunica intima 2. Tunica media 3. Tunica externa posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 7 Tunica Intima (Interna) Tunica intima (interna)—innermost layer Composed of endothelium and basement membrane Damage to endothelium exposes collagen fibers, leading to clot formation  Endothelial cells release endothelins to regulate vasoconstriction Larger arteries contain internal elastic membrane (lamina) Additional layer of elastic fibers Provides additional elasticity to larger arteries Not found in veins posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 8 Tunica Media Tunica media—middle layer Mainly smooth muscle  ▪ Nervi vasorum regulates contraction and relaxation of muscle Leads to vasoconstriction and vasodilation Primarily sympathetic innervation except for external genitalia Thicker tunica media in arteries than veins Larger arteries contain external elastic membrane (lamina) Provides additional elasticity in arteries Not seen in smaller arteries or veins posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 9 Tunica Externa Tunica externa—outermost tunic  Composed mainly of collagen and elastic fibers Maintains shape and structure of vessel Thicker in arteries than in veins Larger arteries and veins are supplied by vasa vasorum Vessels that exchange nutrients and wastes for the wall posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 10 Arteries (Figure 20.5)  Blood vessels that carry blood away from heart Elastic arteries—higher percentage of elastic fibers Help propel blood during ventricular diastole Muscular arteries—higher percentage of smooth muscle Aid in controlling distribution of blood posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 11  Arterioles (Figure 20.5) Microscopic arteries that lead to capillaries All three tunics are very thin Smooth muscle slightly contracted to maintain vascular tone Site of greatest resistance to blood flow Able to regulate blood pressure and distribution of blood flow posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or  publicly accessible website, in whole or in part. 12 Capillaries (1 of 2) (figure 20.6) Thin-walled vessels Used for exchange of substances between blood and tissues Three types: A. Continuous capillaries B. Fenestrated capillaries C. Sinusoid(al) capillaries  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 13 Capillaries (2 of 2) Allow greater exchange of fluid and larger molecules Continuous capillaries—most common Sinusoid(al) capillaries—least type common Complete endothelial lining Large gaps in endothelium and Allows exchange of water, gases, basement membrane and small molecules Found in liver, spleen, and red Fenestrated capillaries—contain pores bone marrow in endothelial lining Found in small intestine and kidneys Allow exchange of plasma  proteins and cells posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 14 Metarterioles and Capillary Beds (Figure 20.7) Metarterioles regulate flow of blood into capillary beds using precapillary sphincters Located at openings of capillary beds from metarteriole Sphincters contract to limit blood flow through capillary  Blood moves through thoroughfare channel bypassing capillary bed When sphincters relax it allows perfusion of capillary beds posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 15 Venules (Figure 20.8) Extremely small veins Merge to form veins Walls consist of: Endothelium  A few bands of smooth muscle Outer layer of connective tissue posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 16 Veins (Figure 20.8) Blood vessels that carry blood toward the heart Thinner walls than arteries Larger lumens Low pressure vessels  Contain valves to prevent backflow Function as blood reservoirs due to larger lumen Venoconstriction speeds up venous return to heart posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 17 Comparison of Arteries and Veins (Table 20.1)  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 18 Alternative Blood Flow Pathways  Typical pattern of blood flow is: Artery, arteriole, capillary bed, venule, then vein A few variations: Arterial anastomosis—multiple arteries supply a common capillary bed ▪ Provides alternate routes for arterial blood to reach tissue Venous anastomosis—venules split and contribute to multiple veins Portal system—links two capillary beds between the artery and vein ▪ Artery, arteriole, capillary bed, connecting vessel, capillary bed, venule, vein posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 19  Anatomy of Blood Flow Pathways Standard pathway of blood flow is arteries, arterioles, capillaries, venules, and veins Alternative pathways of blood flow include: Arterial anastomoses Arteriovenous anastomoses Portal systems posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or  publicly accessible website, in whole or in part. 20 Think, Pair, Share Activity 1 Compare and contrast the structure of an arterial and a venous wall. How are they similar? How are they different?  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 21 Think, Pair, Share Activity 1 Answer Compare and contrast the structure of an arterial and a venous wall. How are they similar? How are they different? The walls of arteries and veins have the same three layers. However, all three layers in the wall of the artery are thicker. The walls of the arteries contain more elastic connective tissue and more smooth muscle. posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 22 Blood Flow, Blood Pressure, and Resistance  Section 20.2 Learning Objectives 20.2.1–20.2.9 Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 23 posted to a publicly accessible website, in whole or in part. Blood Flow Blood flow—the movement of blood through the body Flow rate is influenced by pressure gradient  ▪ Thegreater the resistance, the higher the blood pressure must be to maintain flow ▪ The greater the pressure gradient, the greater the flow rate Flow rate is opposed by resistance ▪ Blood pressure drives blood flow in the human body posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 24 Breakout Group Activity 1 In your group, correlate the action of rolling a marker across the surface of a table to the interaction of blood pressure, blood flow, and vascular resistance.  The marker will represent blood and the surface of the table represents the wall of the vessel. posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 25 Breakout Group Activity 1 Answer In your group, correlate the action of rolling a marker across the surface of a table to the interaction of blood pressure, blood flow, and vascular resistance. The marker will represent blood and the surface of the table represents the wall of the vessel. The push provided to the marker represents blood pressure. The pressure provided makes the marker, representing blood, move or flow. As the marker rolls along the surface of the table, the friction created represents vascular resistance. As the resistance increases, eventually the marker will stop rolling. posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 26 Arterial Blood Pressure  Measured using a sphygmomanometer at the brachial artery Recorded as a ratio of two numbers Systolic pressure reflects pressure during left ventricular systole Diastolic pressure reflects pressure during left ventricular diastole For example: 120/80 mm Hg Topnumber represents systolic pressure, bottom number represents diastolic pressure posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 27  Pulse Pressure (Figure 20.9) Pulse pressure (PP)—difference between systolic and diastolic pressures Highest in arteries closet to heart Disease: decreases with decreased elasticity of arteries ▪ Can occur due to age or chronic high blood pressure  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 28 Mean Arterial Pressure (MAP) Mean arterial pressure (MAP)—“average” pressure arteries experience Calculated by adding diastolic pressure to one-third of pulse pressure MAP = diastolic BP + 1/3 (PP) Homeostatic range for MAP is 70 – 110 mm Hg If measured blood pressure is 120/80 mm Hg, the MAP would be 93.33 mm Hg ▪ 80 + (120-80)/3 = 93.33  ▪ Recall pulse pressure is the difference between systolic and diastolic pressures Low MAP can lead to ischemia due to poor blood flow Ischemia may lead to hypoxia and tissue death posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 29 Pulse (Figure 20.10) The expansion and recoil of arteries as blood flows through them Reflection of heart rate measured in beats per minute (bpm) Can be felt through the skin at superficial arteries  Weaker at points further away from heart Common pulse points are the radial artery (wrist), common carotid artery (neck), and dorsalis pedis artery (foot) posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 30 Variables Affecting Blood Flow and Blood Pressure (Figure 20.11) Pressure must be higher than resistance for blood to flow Factors that influence pressure or resistance will affect flow  Cardiac output Blood volume Vessel compliance Viscosity of blood Blood vessel length and diameter posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 31 Factors that Contribute to the Pressure Gradient Cardiac output (CO)—amount of blood ejected from each ventricle per minute Increased CO increases pressure gradient established by left ventricle and flow rate increases  Decreased CO decreases pressure gradient and flow rate decreases Blood volume—amount of blood within vascular system Lower blood volume (hypovolemia) decreases pressure gradient and flow rate decreases Higher blood volume (hypervolemia) increases pressure gradient and flow rate increases posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 32 Factors that Contribute to Resistance (Figure 20.12) Poiseuille’s equation relates resistance to blood flow  Variables in that equation are: Blood vessel length Blood viscosity Blood vessel radius posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 33 Blood Vessel Length (Figure 20.13) Directly proportional to resistance  Greater total vessel length leads to higher resistance and decreased flow rate Increased amount of vascular wall leads to more interaction between blood and vessel wall This increases friction and, therefore, resistance Individual weight loss can reduce vessel resistance, improving vascular function posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 34 Blood Viscosity  The thickness of blood Directly proportional to resistance More viscous blood leads to higher resistance and decreased flow rate Because more viscous blood moves slower Slower-moving blood creates more friction because it interacts with blood vessel wall longer posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 35  Blood Vessel Radius (Figure 20.14) Inversely proportional to resistance Vessels of smaller diameter (or radius) have higher resistance and decreased flow Less vessel space can increase blood flow along the wall of vessel Contact with wall creates more friction and higher resistance Vessel radius is the most important influence on resistance Arterioles are greatest site of resistance due to small radius and ability to further constrict  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 36 Blood Vessel Radius (2 of 2) (Figure 20.14) Compliance—ability of a vessel to expand to accommodate blood flow Vessels that can easily expand and increase the size of their lumen lower resistance Higher compliance reduces resistance  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 37 Discussion Activity 1 What is the correlation between obesity and higher blood pressure?  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 38 Discussion Activity 1 Answer  What is the correlation between obesity and higher blood pressure? Obesity leads to the growth of new blood vessels to supply the increased adipose tissue. The new vessels increase total blood vessel length and, therefore, vascular resistance. The increase in vascular resistance necessitates an increase in blood pressure to maintain blood flow. posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 39  Blood Velocity (Figure 20.15) Velocity is speed of flow Inversely related to the total cross sectional area of category of vessels Capillaries have greatest total cross sectional area and slowest velocity posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or  publicly accessible website, in whole or in part. 40 Think, Pair, Share Activity 2 Why is the velocity of blood flow slowest in the capillaries?  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 41 Think, Pair, Share Activity 2 Answer Why is the velocity of blood flow slowest in the capillaries?  The velocity of blood flow is slowest in the capillaries to allow for capillary exchange. The primary method of capillary exchange is diffusion. The slower velocity of blood flow allows time for the movement of molecules. posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 42 Application: Hypertension  High blood pressure defined as greater than 140/90 mm Hg persistently More common in biological males than biological females Contributing factors include genetics, obesity, smoking, age, stress, lack of exercise, and alcohol consumption Untreated hypertension may lead to heart, blood vessel, and organ damage Primary hypertension has no identifiable cause (90% of cases) Secondary hypertension has an identifiable cause (10% of cases) Can be managed with lifestyle modifications and medications posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 43  Venous Return (Figure 20.16) Veins are low-pressure vessels Need assistance to move blood toward heart Skeletal muscle pump—muscle compress veins Respiratory pump—alternating pressures milk blood toward heart Valves prevent backflow posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 44 Capillary Exchange Section 20.3 Learning Objectives 20.3.1–20.3.3 Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 45 posted to a publicly accessible website, in whole or in part. Methods of Capillary Exchange  Diffusion—primary method of capillary exchange Molecules move from areas of higher to lower concentration Can be simple diffusion or facilitated Transcytosis—movement through an endothelial cell Endocytosis coupled with exocytosis Bulk flow—exchange of fluid between blood and tissues Driven by hydrostatic and osmotic pressures posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 46  Hydrostatic and Osmotic Pressures Hydrostatic pressure is generated by any fluid within a closed space Blood hydrostatic pressure = force exerted on walls of vessels by blood Drives movement of fluid out of capillaries and into tissues Osmotic pressure is determined by solute concentration Fluid moves toward area of higher solute concentration Most solute concentrations equalize across a capillary wall Plasma proteins do not cross wall of capillary Ensures that solute concentration of blood remains higher than in tissues Drives movement of fluid into capillaries from tissues posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or  publicly accessible website, in whole or in part. 47 Think, Pair, Share Activity 3 How do the thin-walled capillaries help increase the rate of diffusion?  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 48 Think, Pair, Share Activity 3 Answer  How do the thin-walled capillaries help increase the rate of diffusion? The thin walls of capillaries help increase the rate of diffusion by decreasing the diffusion distance. posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 49  Net Filtration Pressure (Figure 20.17) Difference between hydrostatic and osmotic pressures Filtration—fluid leaves blood and enters interstitial fluid (IF) Promoted by blood hydrostatic pressure Reabsorption—fluid leaves IF and enters blood Promoted by colloid osmotic pressure Determined by plasma proteins  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 50 Anatomy of Capillary Transport Capillary exchange occurs primarily via diffusion Exchange also occurs via bulk flow Blood hydrostatic pressure promotes filtration Blood colloid osmotic pressure promotes reabsorption  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 51 Lymphatic Capillaries Hydrostatic pressure exceeds osmotic pressure during bulk flow Imbalance leads to more fluid filtered than reabsorbed The remaining fluid in the tissues would accumulate and cause edema (swelling) if unaccounted for Lymphatic capillaries absorb excess interstitial fluid to prevent edema  Excess interstitial fluid is eventually returned to bloodstream posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 52 Homeostatic Regulation of the Vascular System Section 20.4 Learning Objectives 20.4.1–20.4.6  Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 53 posted to a publicly accessible website, in whole or in part. Neural Regulation Cardiovascular centers in brain regulate blood pressure, distribution, and flow Cardioaccelerator centers—regulate heart rate (HR) and stroke volume Sympathetic cardiac accelerator nerves increase HR and contractility Cardioinhibitory centers—decrease HR and stroke volume Via parasympathetic vagus nerves Vasomotor centers—control vascular tone  Cause vasoconstriction to influence resistance, pressure and flow posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 54 Knowledge Check Activity 1 Where are control centers for nervous system regulation of the vascular system located? A. Hypothalamus B. Pons C. Midbrain  D. Medulla oblongata posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 55 Knowledge Check Activity 1 Answer Where are control centers for nervous system regulation of the vascular system located? D. Medulla oblongata  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 56 Baroreceptor Reflexes (Figure 20.18) Baroreceptors are in aorta and carotid bodies If blood pressure is too high:  Parasympathetic stimulation results in decreased CO and vasodilation If blood pressure is too low: Sympathetic stimulation results in increased CO and vasoconstriction posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 57 Chemoreceptor Reflexes Chemoreceptors:  Located alongside baroreceptors Monitor oxygen, carbon dioxide and pH Communicate with cardioaccelerator, cardioinhibitory, and vasomotor centers Decreased oxygen, increased carbon dioxide, decreased pH All are metabolic wastes from increased activity of muscles As a result, baroreceptors increase BP to increase blood flow to muscles posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 58 Endocrine Regulation  Epinephrine and norepinephrine—increase BP via increased CO and vasoconstriction Antidiuretic hormone—increases BP by increasing blood volume Renin—part of renin-angiotensin-aldosterone pathway that increases BP Angiotensin II—increases BP via vasoconstriction Aldosterone—increases blood volume to increase BP Erythropoietin—increases BP via vasoconstriction Atrial natriuretic hormone—decreases blood volume to decrease BP posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 59  Think, Pair, Share Activity 4 Why do you think most control pathways of the nervous and endocrine systems increase blood pressure? posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or  publicly accessible website, in whole or in part. 60 Think, Pair, Share Activity 4 Answer Why do you think most control pathways of the nervous and endocrine systems increase blood pressure? Most control pathways increase blood pressure because as blood pressure decreases, the flow of blood decreases. This is an emergency situation because if flow is too slow, delivery of oxygen and nutrients to the tissues will be insufficient.  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 61 Autoregulation Local mechanisms that allow tissues to adjust local blood flow Chemical signals open precapillary sphincters of metarterioles to increase flow Low oxygen, increased carbon dioxide, low pH, increasing potassium levels Nitric oxide release results in vasodilation  Chemical signals can also close precapillary sphincters Increased oxygen, decreased carbon dioxide, normal pH posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 62 Myogenic Mechanism Localized response of smooth muscle in arteriole walls Low blood flow through arteriole leads to less wall stretch Smooth muscle relaxes to allow dilation of vessel to increase blood flow Higher blood flow through arteriole increases wall stretch Smooth muscle constricts causing vasoconstriction Reduces amount of blood flow through capillary to protect small vessels from damage posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 63 Factors That Control Peripheral Resistance (Table 20.2) Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 64 Circulatory Pathways  Section 20.5 Learning Objectives 20.5.1–20.5.4 Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 65 posted to a publicly accessible website, in whole or in part. Blood Flow Circuits (Figure 20.19) Systemic circuit delivers nutrients and oxygenated blood to tissues  Pulmonary circuit sends deoxygenated blood to lungs for gas exchange posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 66 The Pulmonary Circuit (Figure 20.20) Pulmonary trunk divides to form  pulmonary arteries that carry deoxygenated blood to lungs Gas exchange occurs in lungs and oxygenated blood is returned to heart via pulmonary veins posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 67 Systemic Arteries (Figure 20.21)  Blood from left atrium enters left ventricle Left ventricle ejects oxygenated blood into systemic arteries Largest artery is the aorta posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 68  The Aorta (Figure 20.22) Emerges from left ventricle of heart Left and right coronary arteries branch from ascending aorta Three branches from aortic arch 1. Brachiocephalic trunk 2. Left common carotid artery 3. Left subclavian artery posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or  publicly accessible website, in whole or in part. 69 The Thoracic and Abdominal Aorta (Figure 20.23) Thoracic aorta descends through thoracic cavity Passes through diaphragm at aortic hiatus Continues as abdominal aorta  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 70 The Coronary Vessels (Figure 20.24) Paired coronary arteries branch from ascending aorta Right coronary artery Left coronary artery  Form the vessels that supply myocardium of the heart posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 71 Arteries Supplying the Head and Neck (Figure 20.25) Subclavian arteries divide to form: Internal thoracic artery, vertebral artery, thyrocervical artery  Common carotid arteries divide to form: Internal carotid artery External carotid artery Branches to form lingual, facial, occipital, maxillary, and superficial temporal arteries posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 72 Arteries of the Brain (Figure 20.26) Arise from internal carotid and vertebral arteries  Vertebral arteries unite to form basilar artery Internal carotid arteries and basilar artery form cerebral arterial circle (i.e., Circle of Willis) posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 73 Cerebral Arterial Circle (Figure 20.27) Internal carotid arteries branch from  common carotid arteries Internal carotid arteries branch to middle and anterior cerebral arteries Vertebral arteries merge to form basilar artery Basilar artery branches to form posterior cerebral arteries Communicating arteries connect major branches posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 74 Arterial Supply of the Thorax and Abdomen (Figure 20.28)  Arteries of thorax and abdominal branch from aorta Celiac trunk branches from abdominal aorta to form: Common hepatic artery Left gastric artery Splenic artery posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 75 Arteries of the Upper Limbs (Figure 20.29)  Subclavian artery Axillary artery Brachial artery Ulnar artery Radial artery Palmar arches Digital arteries posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 76  Arteries of the Lower Limbs (Figure 20.30) Femoral artery Deep femoral artery Popliteal artery Anterior and posterior tibial arteries Dorsalis pedis artery Dorsal and plantar arches posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or  publicly accessible website, in whole or in part. 77 Systemic Veins (Figure 20.31) Return deoxygenated blood to right atrium Many named for the artery they accompany Superior vena cava—drains venous blood above diaphragm Inferior vena cava—drains venous blood below diaphragm  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 78 Superior Vena Cava (Figure 20.32) Subclavian veins merge with internal jugular veins to form brachiocephalic veins Brachiocephalic veins merge to form superior vena cava Azygos veins drain blood from thorax  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 79 Veins of the Head and Neck (Figure 20.33) Internal jugular veins drain brain and some areas of the face Most superficial areas of the head drained by external jugular veins  posted to a Elizabeth Co, Anatomy and Physiology, 1st Edition. © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or publicly accessible website, in whole or in part. 80