{"id":4899,"date":"2019-05-17T17:12:06","date_gmt":"2019-05-17T17:12:06","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/chapter\/blood-flow-blood-pressure-and-resistance-no-content\/"},"modified":"2019-09-01T20:02:18","modified_gmt":"2019-09-01T20:02:18","slug":"blood-flow-blood-pressure-and-resistance-no-content","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/chapter\/blood-flow-blood-pressure-and-resistance-no-content\/","title":{"raw":"Blood Flow, Blood Pressure, and Resistance","rendered":"Blood Flow, Blood Pressure, and Resistance"},"content":{"raw":"<h2>Components of Arterial Blood Pressure<\/h2>\r\nArterial blood pressure in the larger vessels consists of several distinct components: systolic and diastolic pressures, pulse pressure, and mean arterial pressure.\r\n<h3>Systolic and Diastolic Pressures<\/h3>\r\nWhen systemic arterial blood pressure is measured, it is recorded as a ratio of two numbers (e.g., 120\/80 is a normal adult blood pressure), expressed as systolic pressure over diastolic pressure. The systolic pressure is the higher value (typically around 120 mm Hg) and reflects the arterial pressure resulting from the ejection of blood during ventricular contraction, or systole. The diastolic pressure is the lower value (usually about 80 mm Hg) and represents the arterial pressure of blood during ventricular relaxation, or diastole.\r\n\r\n[caption id=\"attachment_1783\" align=\"aligncenter\" width=\"686\"]<img class=\"wp-image-1783 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/230\/2016\/06\/08174230\/Screen-Shot-2016-06-08-at-10.41.46-AM.png\" width=\"686\" height=\"497\" \/> Figure 1. The graph shows the components of blood pressure throughout the blood vessels, including systolic, diastolic, mean arterial, and pulse pressures.[\/caption]\r\n<h3>Pulse Pressure<\/h3>\r\nAs shown in Figure 1, the difference between the systolic pressure and the diastolic pressure is the pulse pressure. For example, an individual with a systolic pressure of 120 mm Hg and a diastolic pressure of 80 mm Hg would have a pulse pressure of 40 mmHg.\r\n<h3>Mean Arterial Pressure<\/h3>\r\nMean arterial pressure (MAP) represents the \u201caverage\u201d pressure of blood in the arteries, that is, the average force driving blood into vessels that serve the tissues. Normally, the MAP falls within the range of 70\u2013110 mm Hg. If the value falls below 60 mm Hg for an extended time, blood pressure will not be high enough to ensure circulation to and through the tissues, which results in ischemia, or insufficient blood flow. A condition called hypoxia, inadequate oxygenation of tissues, commonly accompanies ischemia. The term hypoxemia refers to low levels of oxygen in systemic arterial blood. Neurons are especially sensitive to hypoxia and may die or be damaged if blood flow and oxygen supplies are not quickly restored.\r\n<h2>Pulse<\/h2>\r\nAfter blood is ejected from the heart, elastic fibers in the arteries help maintain a high-pressure gradient as they expand to accommodate the blood, then recoil. This expansion and recoiling effect, known as the pulse, can be palpated manually or measured electronically.\r\n\r\n[caption id=\"attachment_1678\" align=\"aligncenter\" width=\"512\"]<img class=\"wp-image-1678 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/403\/2015\/05\/21032044\/Screen-Shot-2015-05-21-at-10.46.03-AM.png\" alt=\"This image shows the pulse points in a woman\u2019s body.\" width=\"512\" height=\"663\" \/> Figure 2. The pulse is most readily measured at the radial artery, but can be measured at any of the pulse points shown.[\/caption]\r\n\r\nBecause pulse indicates heart rate, it is measured clinically to provide clues to a patient\u2019s state of health. It is recorded as beats per minute. A high or irregular pulse rate can be caused by physical activity or other temporary factors, but it may also indicate a heart condition. The pulse strength indicates the strength of ventricular contraction and cardiac output. If the pulse is strong, then systolic pressure is high. If it is weak, systolic pressure has fallen, and medical intervention may be warranted.\r\n<h2>Measurement of Blood Pressure<\/h2>\r\nBlood pressure is one of the critical parameters measured on virtually every patient in every healthcare setting. The technique used today was developed more than 100 years ago by a pioneering Russian physician, Dr. Nikolai Korotkoff. Turbulent blood flow through the vessels can be heard as a soft ticking while measuring blood pressure; these sounds are known as Korotkoff sounds. The technique of measuring blood pressure requires the use of a sphygmomanometer (a blood pressure cuff attached to a measuring device) and a stethoscope. The technique is as follows:\r\n<ul>\r\n \t<li>The clinician wraps an inflatable cuff tightly around the patient\u2019s arm at about the level of the heart.<\/li>\r\n \t<li>The clinician squeezes a rubber pump to inject air into the cuff, raising pressure around the artery and temporarily cutting off blood flow into the patient\u2019s arm.<\/li>\r\n \t<li>The clinician places the stethoscope on the patient\u2019s antecubital region and, while gradually allowing air within the cuff to escape, listens for the Korotkoff sounds.<\/li>\r\n<\/ul>\r\nAlthough there are five recognized Korotkoff sounds, only two are normally recorded. Initially, no sounds are heard since there is no blood flow through the vessels, but as air pressure drops, the cuff relaxes, and blood flow returns to the arm. As shown in Figure 3, the first sound heard through the stethoscope\u2014the first Korotkoff sound\u2014indicates systolic pressure. As more air is released from the cuff, blood is able to flow freely through the brachial artery and all sounds disappear. The point at which the last sound is heard is recorded as the patient\u2019s diastolic pressure.\r\n\r\n[caption id=\"attachment_1679\" align=\"aligncenter\" width=\"679\"]<img class=\"wp-image-1679 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/403\/2015\/05\/21032046\/Screen-Shot-2015-05-21-at-10.47.45-AM.png\" alt=\"This image shows blood pressure as a function of time.\" width=\"679\" height=\"401\" \/> Figure 3. When pressure in a sphygmomanometer cuff is released, a clinician can hear the Korotkoff sounds. In this graph, a blood pressure tracing is aligned to a measurement of systolic and diastolic pressures.[\/caption]\r\n\r\nFigure 4 compares vessel diameter, total cross-sectional area, average blood pressure, and blood velocity through the systemic vessels. Notice in parts (a) and (b) that the total cross-sectional area of the body\u2019s capillary beds is far greater than any other type of vessel. Although the diameter of an individual capillary is significantly smaller than the diameter of an arteriole, there are vastly more capillaries in the body than there are other types of blood vessels. Part (c) shows that blood pressure drops unevenly as blood travels from arteries to arterioles, capillaries, venules, and veins, and encounters greater resistance. However, the site of the most precipitous drop, and the site of greatest resistance, is the arterioles. This explains why vasodilation and vasoconstriction of arterioles play more significant roles in regulating blood pressure than do the vasodilation and vasoconstriction of other vessels.\r\n\r\n[caption id=\"attachment_1680\" align=\"aligncenter\" width=\"733\"]<img class=\"wp-image-1680 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/403\/2015\/05\/21032047\/Screen-Shot-2015-05-21-at-10.51.41-AM.png\" alt=\"Relationship among Vessels in the Systemic Circuit\" width=\"733\" height=\"509\" \/> Figure 4. The relationships among blood vessels that can be compared include (a) vessel diameter, (b) total cross-sectional area, (c) average blood pressure, and (d) velocity of blood flow.[\/caption]\r\n\r\nPart (d) shows that the velocity (speed) of blood flow decreases dramatically as the blood moves from arteries to arterioles to capillaries. This slow flow rate allows more time for exchange processes to occur. As blood flows through the veins, the rate of velocity increases, as blood is returned to the heart.\r\n<div class=\"textbox examples\">\r\n<h3>Disorders of the Cardiovascular System: Arteriosclerosis<\/h3>\r\nCompliance allows an artery to expand when blood is pumped through it from the heart, and then to recoil after the surge has passed. This helps promote blood flow. In arteriosclerosis, compliance is reduced, and pressure and resistance within the vessel increase. This is a leading cause of hypertension and coronary heart disease, as it causes the heart to work harder to generate a pressure great enough to overcome the resistance.\r\n\r\nArteriosclerosis begins with injury to the endothelium of an artery, which may be caused by irritation from high blood glucose, infection, tobacco use, excessive blood lipids, and other factors. Artery walls that are constantly stressed by blood flowing at high pressure are also more likely to be injured\u2014which means that hypertension can promote arteriosclerosis, as well as result from it.\r\n\r\nRecall that tissue injury causes inflammation. As inflammation spreads into the artery wall, it weakens and scars it, leaving it stiff (sclerotic). As a result, compliance is reduced. Moreover, circulating triglycerides and cholesterol can seep between the damaged lining cells and become trapped within the artery wall, where they are frequently joined by leukocytes, calcium, and cellular debris. Eventually, this buildup, called plaque, can narrow arteries enough to impair blood flow. The term for this condition, atherosclerosis (athero- = \u201cporridge\u201d) describes the mealy deposits.\r\n\r\n[caption id=\"attachment_1681\" align=\"aligncenter\" width=\"693\"]<img class=\"wp-image-1681 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/403\/2015\/05\/21032049\/Screen-Shot-2015-05-21-at-10.57.13-AM.png\" alt=\"Image of normal artery and artery narrowed by plaque from artherosclerosis.\" width=\"693\" height=\"378\" \/> Figure 5. <em>Atherosclerosis<\/em>. (a) Atherosclerosis can result from plaques formed by the buildup of fatty, calcified deposits in an artery. (b) Plaques can also take other forms, as shown in this micrograph of a coronary artery that has a buildup of connective tissue within the artery wall. LM \u00d7 40. (Micrograph provided by the Regents of University of Michigan Medical School \u00a9 2012)[\/caption]\r\n\r\n&nbsp;\r\n\r\nSometimes a plaque can rupture, causing microscopic tears in the artery wall that allow blood to leak into the tissue on the other side. When this happens, platelets rush to the site to clot the blood. This clot can further obstruct the artery and\u2014if it occurs in a coronary or cerebral artery\u2014cause a sudden heart attack or stroke. Alternatively, plaque can break off and travel through the bloodstream as an embolus until it blocks a more distant, smaller artery.\r\n\r\nEven without total blockage, vessel narrowing leads to ischemia\u2014reduced blood flow\u2014to the tissue region \u201cdownstream\u201d of the narrowed vessel. Ischemia in turn leads to hypoxia\u2014decreased supply of oxygen to the tissues. Hypoxia involving cardiac muscle or brain tissue can lead to cell death and severe impairment of brain or heart function.\r\n\r\nA major risk factor for both arteriosclerosis and atherosclerosis is advanced age, as the conditions tend to progress over time. Arteriosclerosis is normally defined as the more generalized loss of compliance, \u201chardening of the arteries,\u201d whereas atherosclerosis is a more specific term for the build-up of plaque in the walls of the vessel and is a specific type of arteriosclerosis. There is also a distinct genetic component, and pre-existing hypertension and\/or diabetes also greatly increase the risk. However, obesity, poor nutrition, lack of physical activity, and tobacco use all are major risk factors.\r\n\r\nTreatment includes lifestyle changes, such as weight loss, smoking cessation, regular exercise, and adoption of a diet low in sodium and saturated fats. Medications to reduce cholesterol and blood pressure may be prescribed. For blocked coronary arteries, surgery is warranted. In angioplasty, a catheter is inserted into the vessel at the point of narrowing, and a second catheter with a balloon-like tip is inflated to widen the opening. To prevent subsequent collapse of the vessel, a small mesh tube called a stent is often inserted. In an endarterectomy, plaque is surgically removed from the walls of a vessel. This operation is typically performed on the carotid arteries of the neck, which are a prime source of oxygenated blood for the brain. In a coronary bypass procedure, a non-vital superficial vessel from another part of the body (often the great saphenous vein) or a synthetic vessel is inserted to create a path around the blocked area of a coronary artery.\r\n\r\n<\/div>","rendered":"<h2>Components of Arterial Blood Pressure<\/h2>\n<p>Arterial blood pressure in the larger vessels consists of several distinct components: systolic and diastolic pressures, pulse pressure, and mean arterial pressure.<\/p>\n<h3>Systolic and Diastolic Pressures<\/h3>\n<p>When systemic arterial blood pressure is measured, it is recorded as a ratio of two numbers (e.g., 120\/80 is a normal adult blood pressure), expressed as systolic pressure over diastolic pressure. The systolic pressure is the higher value (typically around 120 mm Hg) and reflects the arterial pressure resulting from the ejection of blood during ventricular contraction, or systole. The diastolic pressure is the lower value (usually about 80 mm Hg) and represents the arterial pressure of blood during ventricular relaxation, or diastole.<\/p>\n<div id=\"attachment_1783\" style=\"width: 696px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1783\" class=\"wp-image-1783 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/230\/2016\/06\/08174230\/Screen-Shot-2016-06-08-at-10.41.46-AM.png\" width=\"686\" height=\"497\" alt=\"image\" \/><\/p>\n<p id=\"caption-attachment-1783\" class=\"wp-caption-text\">Figure 1. The graph shows the components of blood pressure throughout the blood vessels, including systolic, diastolic, mean arterial, and pulse pressures.<\/p>\n<\/div>\n<h3>Pulse Pressure<\/h3>\n<p>As shown in Figure 1, the difference between the systolic pressure and the diastolic pressure is the pulse pressure. For example, an individual with a systolic pressure of 120 mm Hg and a diastolic pressure of 80 mm Hg would have a pulse pressure of 40 mmHg.<\/p>\n<h3>Mean Arterial Pressure<\/h3>\n<p>Mean arterial pressure (MAP) represents the \u201caverage\u201d pressure of blood in the arteries, that is, the average force driving blood into vessels that serve the tissues. Normally, the MAP falls within the range of 70\u2013110 mm Hg. If the value falls below 60 mm Hg for an extended time, blood pressure will not be high enough to ensure circulation to and through the tissues, which results in ischemia, or insufficient blood flow. A condition called hypoxia, inadequate oxygenation of tissues, commonly accompanies ischemia. The term hypoxemia refers to low levels of oxygen in systemic arterial blood. Neurons are especially sensitive to hypoxia and may die or be damaged if blood flow and oxygen supplies are not quickly restored.<\/p>\n<h2>Pulse<\/h2>\n<p>After blood is ejected from the heart, elastic fibers in the arteries help maintain a high-pressure gradient as they expand to accommodate the blood, then recoil. This expansion and recoiling effect, known as the pulse, can be palpated manually or measured electronically.<\/p>\n<div id=\"attachment_1678\" style=\"width: 522px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1678\" class=\"wp-image-1678 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/403\/2015\/05\/21032044\/Screen-Shot-2015-05-21-at-10.46.03-AM.png\" alt=\"This image shows the pulse points in a woman\u2019s body.\" width=\"512\" height=\"663\" \/><\/p>\n<p id=\"caption-attachment-1678\" class=\"wp-caption-text\">Figure 2. The pulse is most readily measured at the radial artery, but can be measured at any of the pulse points shown.<\/p>\n<\/div>\n<p>Because pulse indicates heart rate, it is measured clinically to provide clues to a patient\u2019s state of health. It is recorded as beats per minute. A high or irregular pulse rate can be caused by physical activity or other temporary factors, but it may also indicate a heart condition. The pulse strength indicates the strength of ventricular contraction and cardiac output. If the pulse is strong, then systolic pressure is high. If it is weak, systolic pressure has fallen, and medical intervention may be warranted.<\/p>\n<h2>Measurement of Blood Pressure<\/h2>\n<p>Blood pressure is one of the critical parameters measured on virtually every patient in every healthcare setting. The technique used today was developed more than 100 years ago by a pioneering Russian physician, Dr. Nikolai Korotkoff. Turbulent blood flow through the vessels can be heard as a soft ticking while measuring blood pressure; these sounds are known as Korotkoff sounds. The technique of measuring blood pressure requires the use of a sphygmomanometer (a blood pressure cuff attached to a measuring device) and a stethoscope. The technique is as follows:<\/p>\n<ul>\n<li>The clinician wraps an inflatable cuff tightly around the patient\u2019s arm at about the level of the heart.<\/li>\n<li>The clinician squeezes a rubber pump to inject air into the cuff, raising pressure around the artery and temporarily cutting off blood flow into the patient\u2019s arm.<\/li>\n<li>The clinician places the stethoscope on the patient\u2019s antecubital region and, while gradually allowing air within the cuff to escape, listens for the Korotkoff sounds.<\/li>\n<\/ul>\n<p>Although there are five recognized Korotkoff sounds, only two are normally recorded. Initially, no sounds are heard since there is no blood flow through the vessels, but as air pressure drops, the cuff relaxes, and blood flow returns to the arm. As shown in Figure 3, the first sound heard through the stethoscope\u2014the first Korotkoff sound\u2014indicates systolic pressure. As more air is released from the cuff, blood is able to flow freely through the brachial artery and all sounds disappear. The point at which the last sound is heard is recorded as the patient\u2019s diastolic pressure.<\/p>\n<div id=\"attachment_1679\" style=\"width: 689px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1679\" class=\"wp-image-1679 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/403\/2015\/05\/21032046\/Screen-Shot-2015-05-21-at-10.47.45-AM.png\" alt=\"This image shows blood pressure as a function of time.\" width=\"679\" height=\"401\" \/><\/p>\n<p id=\"caption-attachment-1679\" class=\"wp-caption-text\">Figure 3. When pressure in a sphygmomanometer cuff is released, a clinician can hear the Korotkoff sounds. In this graph, a blood pressure tracing is aligned to a measurement of systolic and diastolic pressures.<\/p>\n<\/div>\n<p>Figure 4 compares vessel diameter, total cross-sectional area, average blood pressure, and blood velocity through the systemic vessels. Notice in parts (a) and (b) that the total cross-sectional area of the body\u2019s capillary beds is far greater than any other type of vessel. Although the diameter of an individual capillary is significantly smaller than the diameter of an arteriole, there are vastly more capillaries in the body than there are other types of blood vessels. Part (c) shows that blood pressure drops unevenly as blood travels from arteries to arterioles, capillaries, venules, and veins, and encounters greater resistance. However, the site of the most precipitous drop, and the site of greatest resistance, is the arterioles. This explains why vasodilation and vasoconstriction of arterioles play more significant roles in regulating blood pressure than do the vasodilation and vasoconstriction of other vessels.<\/p>\n<div id=\"attachment_1680\" style=\"width: 743px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1680\" class=\"wp-image-1680 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/403\/2015\/05\/21032047\/Screen-Shot-2015-05-21-at-10.51.41-AM.png\" alt=\"Relationship among Vessels in the Systemic Circuit\" width=\"733\" height=\"509\" \/><\/p>\n<p id=\"caption-attachment-1680\" class=\"wp-caption-text\">Figure 4. The relationships among blood vessels that can be compared include (a) vessel diameter, (b) total cross-sectional area, (c) average blood pressure, and (d) velocity of blood flow.<\/p>\n<\/div>\n<p>Part (d) shows that the velocity (speed) of blood flow decreases dramatically as the blood moves from arteries to arterioles to capillaries. This slow flow rate allows more time for exchange processes to occur. As blood flows through the veins, the rate of velocity increases, as blood is returned to the heart.<\/p>\n<div class=\"textbox examples\">\n<h3>Disorders of the Cardiovascular System: Arteriosclerosis<\/h3>\n<p>Compliance allows an artery to expand when blood is pumped through it from the heart, and then to recoil after the surge has passed. This helps promote blood flow. In arteriosclerosis, compliance is reduced, and pressure and resistance within the vessel increase. This is a leading cause of hypertension and coronary heart disease, as it causes the heart to work harder to generate a pressure great enough to overcome the resistance.<\/p>\n<p>Arteriosclerosis begins with injury to the endothelium of an artery, which may be caused by irritation from high blood glucose, infection, tobacco use, excessive blood lipids, and other factors. Artery walls that are constantly stressed by blood flowing at high pressure are also more likely to be injured\u2014which means that hypertension can promote arteriosclerosis, as well as result from it.<\/p>\n<p>Recall that tissue injury causes inflammation. As inflammation spreads into the artery wall, it weakens and scars it, leaving it stiff (sclerotic). As a result, compliance is reduced. Moreover, circulating triglycerides and cholesterol can seep between the damaged lining cells and become trapped within the artery wall, where they are frequently joined by leukocytes, calcium, and cellular debris. Eventually, this buildup, called plaque, can narrow arteries enough to impair blood flow. The term for this condition, atherosclerosis (athero- = \u201cporridge\u201d) describes the mealy deposits.<\/p>\n<div id=\"attachment_1681\" style=\"width: 703px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1681\" class=\"wp-image-1681 size-full\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images-archive-read-only\/wp-content\/uploads\/sites\/403\/2015\/05\/21032049\/Screen-Shot-2015-05-21-at-10.57.13-AM.png\" alt=\"Image of normal artery and artery narrowed by plaque from artherosclerosis.\" width=\"693\" height=\"378\" \/><\/p>\n<p id=\"caption-attachment-1681\" class=\"wp-caption-text\">Figure 5. <em>Atherosclerosis<\/em>. (a) Atherosclerosis can result from plaques formed by the buildup of fatty, calcified deposits in an artery. (b) Plaques can also take other forms, as shown in this micrograph of a coronary artery that has a buildup of connective tissue within the artery wall. LM \u00d7 40. (Micrograph provided by the Regents of University of Michigan Medical School \u00a9 2012)<\/p>\n<\/div>\n<p>&nbsp;<\/p>\n<p>Sometimes a plaque can rupture, causing microscopic tears in the artery wall that allow blood to leak into the tissue on the other side. When this happens, platelets rush to the site to clot the blood. This clot can further obstruct the artery and\u2014if it occurs in a coronary or cerebral artery\u2014cause a sudden heart attack or stroke. Alternatively, plaque can break off and travel through the bloodstream as an embolus until it blocks a more distant, smaller artery.<\/p>\n<p>Even without total blockage, vessel narrowing leads to ischemia\u2014reduced blood flow\u2014to the tissue region \u201cdownstream\u201d of the narrowed vessel. Ischemia in turn leads to hypoxia\u2014decreased supply of oxygen to the tissues. Hypoxia involving cardiac muscle or brain tissue can lead to cell death and severe impairment of brain or heart function.<\/p>\n<p>A major risk factor for both arteriosclerosis and atherosclerosis is advanced age, as the conditions tend to progress over time. Arteriosclerosis is normally defined as the more generalized loss of compliance, \u201chardening of the arteries,\u201d whereas atherosclerosis is a more specific term for the build-up of plaque in the walls of the vessel and is a specific type of arteriosclerosis. There is also a distinct genetic component, and pre-existing hypertension and\/or diabetes also greatly increase the risk. However, obesity, poor nutrition, lack of physical activity, and tobacco use all are major risk factors.<\/p>\n<p>Treatment includes lifestyle changes, such as weight loss, smoking cessation, regular exercise, and adoption of a diet low in sodium and saturated fats. Medications to reduce cholesterol and blood pressure may be prescribed. For blocked coronary arteries, surgery is warranted. In angioplasty, a catheter is inserted into the vessel at the point of narrowing, and a second catheter with a balloon-like tip is inflated to widen the opening. To prevent subsequent collapse of the vessel, a small mesh tube called a stent is often inserted. In an endarterectomy, plaque is surgically removed from the walls of a vessel. This operation is typically performed on the carotid arteries of the neck, which are a prime source of oxygenated blood for the brain. In a coronary bypass procedure, a non-vital superficial vessel from another part of the body (often the great saphenous vein) or a synthetic vessel is inserted to create a path around the blocked area of a coronary artery.<\/p>\n<\/div>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-4899\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Anatomy &amp; Physiology. <strong>Provided by<\/strong>: OpenStax CNX. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/cnx.org\/contents\/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@8.25\">http:\/\/cnx.org\/contents\/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@8.25<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em>. <strong>License Terms<\/strong>: Download for free at http:\/\/cnx.org\/contents\/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@8.25<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":141992,"menu_order":7,"template":"","meta":{"_candela_citation":"[{\"type\":\"cc\",\"description\":\"Anatomy & Physiology\",\"author\":\"\",\"organization\":\"OpenStax CNX\",\"url\":\"http:\/\/cnx.org\/contents\/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@8.25\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"Download for free at http:\/\/cnx.org\/contents\/14fb4ad7-39a1-4eee-ab6e-3ef2482e3e22@8.25\"}]","CANDELA_OUTCOMES_GUID":"","pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-4899","chapter","type-chapter","status-publish","hentry"],"part":4890,"_links":{"self":[{"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/pressbooks\/v2\/chapters\/4899","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/wp\/v2\/users\/141992"}],"version-history":[{"count":3,"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/pressbooks\/v2\/chapters\/4899\/revisions"}],"predecessor-version":[{"id":6092,"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/pressbooks\/v2\/chapters\/4899\/revisions\/6092"}],"part":[{"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/pressbooks\/v2\/parts\/4890"}],"metadata":[{"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/pressbooks\/v2\/chapters\/4899\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/wp\/v2\/media?parent=4899"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/pressbooks\/v2\/chapter-type?post=4899"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/wp\/v2\/contributor?post=4899"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/courses.lumenlearning.com\/suny-dutchess-ap1\/wp-json\/wp\/v2\/license?post=4899"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}