{"id":3231,"date":"2022-08-22T18:00:25","date_gmt":"2022-08-22T22:00:25","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/pathology\/?post_type=chapter&#038;p=3231"},"modified":"2025-11-15T19:24:44","modified_gmt":"2025-11-16T00:24:44","slug":"gross-anatomy-of-atherosclerosis","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/pathology\/chapter\/gross-anatomy-of-atherosclerosis\/","title":{"raw":"Histopathology of Atherosclerosis","rendered":"Histopathology of Atherosclerosis"},"content":{"raw":"<div class=\"textbox textbox--learning-objectives\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Learning Objectives<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nBy the end of this chapter, you will be able to:\r\n<ul>\r\n \t<li>Relate key pathophysiological changes in the progression of atherosclerosis to the cell\/tissue changes visible on the histological slide.<\/li>\r\n \t<li>Interpret lipid and elastin histological stains.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n<h2>Histopathology of Atherosclerosis<\/h2>\r\nWe will examine the histopathology of atherosclerosis using two slides of[pb_glossary id=\"3923\"] atheroma[\/pb_glossary] of the aorta coming from the same patient - a 65 y.o. man with a history of [pb_glossary id=\"3893\"]hypertension[\/pb_glossary] - one of the main risk factors of atherosclerosis.\r\n\r\nBoth slides are stained with special stains (fat stain and elastic tissue stain) that allow for visualization of specific tissue components that would not be clearly identifiable by the classic H&amp;E stain.\r\n\r\nWhile examining tissue slides, please note <em><strong>epithelial damage - <\/strong><\/em>an initial step of atherosclerosis progression that triggers subsequent inflammation and atherosclerotic plaque formation.\r\n\r\n&nbsp;\r\n\r\n[h5p id=\"184\"]\r\n<p style=\"background-color: #f0f0f0;padding: 5px;text-align: left\"><sup><strong>Histopathology of atherosclerosis (aorta)<\/strong> by Tetiana Povshedna licensed under CC BY 4.0 created with BioRender.com. Histology slides are DHPLC specimens PATH 425-032 (fat stain) and PATH 425-033 (elastin stain)<\/sup><\/p>\r\n\r\n<div>\r\n\r\n&nbsp;\r\n<div class=\"textbox textbox--key-takeaways\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Fat Tissue Stain: Key Takeawats<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n<ul>\r\n \t<li>Irregularly thickened [pb_glossary id=\"2208\"]tunica intima[\/pb_glossary] as a result of lipid accumulation<\/li>\r\n \t<li>Numerous lipid deposits in both [pb_glossary id=\"2208\"]tunica intima[\/pb_glossary] and [pb_glossary id=\"2209\"]tunica media[\/pb_glossary]<\/li>\r\n<\/ul>\r\nOn a cellular level, this stage of atherosclerosis development is associated with the pro-inflammatory state, macrophage recruitment, and foam cell formation with subsequent necrotic core development.\r\n\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox textbox--key-takeaways\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Elastin Stain: Key Takeaways <span style=\"text-align: initial;color: #000000;font-size: 1em;font-style: normal\">.<\/span><\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n<ul>\r\n \t<li>Irregularly thickened [pb_glossary id=\"2208\"]tunica intima[\/pb_glossary]; loss of elastic fibers in tunica intima (compare this elastic stain to an example of the normal human aorta in <a href=\"\/\/chapter\/normal-blood-vessel-anatomy-histology\/\">Gross anatomy and histology of normal aorta<\/a> and note the amount of elastic fibers in tunica intima)<\/li>\r\n \t<li>Elastic tissue appears compressed and fragmented in the superficial layers of [pb_glossary id=\"2209\"]tunica media[\/pb_glossary]. This fragmentation and weakening of the aorta wall might facilitate the formation of [pb_glossary id=\"3914\"]aneurysm\u00a0[\/pb_glossary]<\/li>\r\n \t<li>On higher magnification, cholesterol crystals appear as stellate empty spaces in [pb_glossary id=\"2208\"]tunica intima[\/pb_glossary]<\/li>\r\n \t<li>Areas of calcification appear as dark dense spots within tunica intima<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\nWhile all the histological slides and gross anatomy specimens above focused on various regions of aorta as a site of atherosclerotic plaque formation, coronary arteries are also one of the common and clinically relevant sites of atherosclerosis. Plaque formation within these arteries can cause [pb_glossary id=\"3862\"]hypoxia[\/pb_glossary] of the heart muscle which, if left untreated, can lead to a heart attack.\r\n\r\nThe video below examines the key features of atherosclerosis in [pb_glossary id=\"2100\"]coronary arteries[\/pb_glossary]. Clinically, these changes would reflect the pathophysiology of ischemic heart disease.\r\n\r\n&nbsp;\r\n\r\n<\/div>\r\n<div>[h5p id=\"67\"]<\/div>\r\n<div>\r\n<p style=\"background-color: #f0f0f0;padding: 5px;text-align: left\"><sup><em><strong>Histopathology of atherosclerosis (coronary artery).<\/strong> Created and presented by Jonathan Bush. Histology slide is from private collection.\u00a0<\/em>\r\n<\/sup><\/p>\r\n\r\n<\/div>\r\n<div class=\"textbox textbox--key-takeaways\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Key Takeaways<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n<ul>\r\n \t<li>Numerous immune cells in [pb_glossary id=\"2207\"]tunica externa [\/pb_glossary]reflect inflammatory process triggered by atherosclerosis.<\/li>\r\n \t<li>A blood clot is obstructing the lumen, making tunica intima hard to identify.<\/li>\r\n \t<li>Fibrotic areas (appear pale pink and do not contain a lot of cell nuclei) reflect lipid accumulation.<\/li>\r\n \t<li>Foam cells that engulfed oxidized LDL in [pb_glossary id=\"2209\"]tunica media [\/pb_glossary].<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\n&nbsp;\r\n<h2>Section Review<\/h2>\r\nOn gross anatomy specimens, early atherosclerotic lesions appear as yellow streaks\/patches on the luminal side of the vessel. As the severity of atherosclerosis increases, atherosclerotic plaques grow in size and number and can cause ulceration. Advanced atherosclerotic vessels have an irregular luminal surface, numerous plaques, areas of calcification, ulceration, and clot formation. One of the most common clinical outcomes of advanced atherosclerosis is an aneurysm or clot formation.\r\n\r\nHistologically, lipid deposits are visible within the [pb_glossary id=\"2208\"] tunica intima[\/pb_glossary] and [pb_glossary id=\"2209\"]tunica media [\/pb_glossary] of atherosclerotic vessels. Endothelial damage, which is necessary for lesion initiation, is often present. During the advanced stages, cholesterol crystals and calcium deposits can be visualized in [pb_glossary id=\"2208\"]tunica intima[\/pb_glossary], while [pb_glossary id=\"2209\"]tunica media[\/pb_glossary] can appear fragmented.\r\n<h1>Review Questions<\/h1>\r\n<div class=\"h5p\">[h5p id=\"192\"]<\/div>\r\n<div class=\"pdf\">\r\n\r\n<strong>1. Fill in the blanks.<\/strong>On gross anatomy specimens, atherosclerotic plaques appear as _____ lesions. (<em>indicate colour<\/em>)\r\n\r\n<strong>2. Finish the following sentence. Common clinical outcomes of advanced atherosclerosis include:<\/strong>\r\n<strong>Select all that apply.<\/strong>\r\n<ul>\r\n \t<li>Aneurysm formation<\/li>\r\n \t<li>Clot formation<\/li>\r\n \t<li>Decreased blood pressure<\/li>\r\n \t<li>Arythmias<\/li>\r\n<\/ul>\r\n<strong>3. Fill in the blank.<\/strong>\r\n\r\nAs atherosclerosis progresses, _____ can form on the luminal surface of the vessel, exposing underlying layers of the vessel wall.\r\n\r\n<strong>4. Finish the following sentence. Aneurysm is usually a consequences of a weakened:<\/strong>\r\n<ul>\r\n \t<li>Tunica intima<\/li>\r\n \t<li>Tunica media<\/li>\r\n \t<li>Tunica externa<\/li>\r\n<\/ul>\r\n<strong>5. Fill in the blank.<\/strong>\r\n\r\n_____ damage is necessary for atherosclerotic lesion initiation.\r\n\r\n<strong>6. In atherosclerosis, lipid deposits can accumulate in both tunica intima and tunica media.<\/strong>\r\n<ul>\r\n \t<li>True<\/li>\r\n \t<li>False<\/li>\r\n<\/ul>\r\n<strong>7. Fill in the blank.<\/strong>\r\n\r\n_____ deposits in advanced atherosclerosis harden the vessel wall and make it brittle.\r\n\r\n&nbsp;\r\n<div class=\"textbox\">\r\n<h2>Answer Key<\/h2>\r\n<ol>\r\n \t<li>Yellow<\/li>\r\n \t<li>Aneurysm formation, clot formation<\/li>\r\n \t<li>Ulcers<\/li>\r\n \t<li>Tunica media<\/li>\r\n \t<li>Endothelial<\/li>\r\n \t<li>True<\/li>\r\n \t<li>Calcium<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>","rendered":"<div class=\"textbox textbox--learning-objectives\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Learning Objectives<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>By the end of this chapter, you will be able to:<\/p>\n<ul>\n<li>Relate key pathophysiological changes in the progression of atherosclerosis to the cell\/tissue changes visible on the histological slide.<\/li>\n<li>Interpret lipid and elastin histological stains.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<h2>Histopathology of Atherosclerosis<\/h2>\n<p>We will examine the histopathology of atherosclerosis using two slides of<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_3923\"> atheroma<\/a> of the aorta coming from the same patient &#8211; a 65 y.o. man with a history of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_3893\">hypertension<\/a> &#8211; one of the main risk factors of atherosclerosis.<\/p>\n<p>Both slides are stained with special stains (fat stain and elastic tissue stain) that allow for visualization of specific tissue components that would not be clearly identifiable by the classic H&amp;E stain.<\/p>\n<p>While examining tissue slides, please note <em><strong>epithelial damage &#8211; <\/strong><\/em>an initial step of atherosclerosis progression that triggers subsequent inflammation and atherosclerotic plaque formation.<\/p>\n<p>&nbsp;<\/p>\n<div id=\"h5p-184\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-184\" class=\"h5p-iframe\" data-content-id=\"184\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Histopathology of atherosclerosis (aorta)\"><\/iframe><\/div>\n<\/div>\n<p style=\"background-color: #f0f0f0;padding: 5px;text-align: left\"><sup><strong>Histopathology of atherosclerosis (aorta)<\/strong> by Tetiana Povshedna licensed under CC BY 4.0 created with BioRender.com. Histology slides are DHPLC specimens PATH 425-032 (fat stain) and PATH 425-033 (elastin stain)<\/sup><\/p>\n<div>\n<p>&nbsp;<\/p>\n<div class=\"textbox textbox--key-takeaways\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Fat Tissue Stain: Key Takeawats<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n<li>Irregularly thickened <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2208\">tunica intima<\/a> as a result of lipid accumulation<\/li>\n<li>Numerous lipid deposits in both <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2208\">tunica intima<\/a> and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2209\">tunica media<\/a><\/li>\n<\/ul>\n<p>On a cellular level, this stage of atherosclerosis development is associated with the pro-inflammatory state, macrophage recruitment, and foam cell formation with subsequent necrotic core development.<\/p>\n<\/div>\n<\/div>\n<div class=\"textbox textbox--key-takeaways\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Elastin Stain: Key Takeaways <span style=\"text-align: initial;color: #000000;font-size: 1em;font-style: normal\">.<\/span><\/p>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n<li>Irregularly thickened <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2208\">tunica intima<\/a>; loss of elastic fibers in tunica intima (compare this elastic stain to an example of the normal human aorta in <a href=\"\/\/chapter\/normal-blood-vessel-anatomy-histology\/\">Gross anatomy and histology of normal aorta<\/a> and note the amount of elastic fibers in tunica intima)<\/li>\n<li>Elastic tissue appears compressed and fragmented in the superficial layers of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2209\">tunica media<\/a>. This fragmentation and weakening of the aorta wall might facilitate the formation of <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_3914\">aneurysm\u00a0<\/a><\/li>\n<li>On higher magnification, cholesterol crystals appear as stellate empty spaces in <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2208\">tunica intima<\/a><\/li>\n<li>Areas of calcification appear as dark dense spots within tunica intima<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p>While all the histological slides and gross anatomy specimens above focused on various regions of aorta as a site of atherosclerotic plaque formation, coronary arteries are also one of the common and clinically relevant sites of atherosclerosis. Plaque formation within these arteries can cause <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_3862\">hypoxia<\/a> of the heart muscle which, if left untreated, can lead to a heart attack.<\/p>\n<p>The video below examines the key features of atherosclerosis in <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2100\">coronary arteries<\/a>. Clinically, these changes would reflect the pathophysiology of ischemic heart disease.<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<div>\n<div id=\"h5p-67\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-67\" class=\"h5p-iframe\" data-content-id=\"67\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Histopathology of Atherosclerosis (coronary artery)\"><\/iframe><\/div>\n<\/div>\n<\/div>\n<div>\n<p style=\"background-color: #f0f0f0;padding: 5px;text-align: left\"><sup><em><strong>Histopathology of atherosclerosis (coronary artery).<\/strong> Created and presented by Jonathan Bush. Histology slide is from private collection.\u00a0<\/em><br \/>\n<\/sup><\/p>\n<\/div>\n<div class=\"textbox textbox--key-takeaways\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Key Takeaways<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<ul>\n<li>Numerous immune cells in <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2207\">tunica externa <\/a>reflect inflammatory process triggered by atherosclerosis.<\/li>\n<li>A blood clot is obstructing the lumen, making tunica intima hard to identify.<\/li>\n<li>Fibrotic areas (appear pale pink and do not contain a lot of cell nuclei) reflect lipid accumulation.<\/li>\n<li>Foam cells that engulfed oxidized LDL in <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2209\">tunica media <\/a>.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<h2>Section Review<\/h2>\n<p>On gross anatomy specimens, early atherosclerotic lesions appear as yellow streaks\/patches on the luminal side of the vessel. As the severity of atherosclerosis increases, atherosclerotic plaques grow in size and number and can cause ulceration. Advanced atherosclerotic vessels have an irregular luminal surface, numerous plaques, areas of calcification, ulceration, and clot formation. One of the most common clinical outcomes of advanced atherosclerosis is an aneurysm or clot formation.<\/p>\n<p>Histologically, lipid deposits are visible within the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2208\"> tunica intima<\/a> and <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2209\">tunica media <\/a> of atherosclerotic vessels. Endothelial damage, which is necessary for lesion initiation, is often present. During the advanced stages, cholesterol crystals and calcium deposits can be visualized in <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2208\">tunica intima<\/a>, while <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_3231_2209\">tunica media<\/a> can appear fragmented.<\/p>\n<h1>Review Questions<\/h1>\n<div class=\"h5p\">\n<div id=\"h5p-192\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-192\" class=\"h5p-iframe\" data-content-id=\"192\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Histopath of atherosclerosis\"><\/iframe><\/div>\n<\/div>\n<\/div>\n<div class=\"pdf\">\n<p><strong>1. Fill in the blanks.<\/strong>On gross anatomy specimens, atherosclerotic plaques appear as _____ lesions. (<em>indicate colour<\/em>)<\/p>\n<p><strong>2. Finish the following sentence. Common clinical outcomes of advanced atherosclerosis include:<\/strong><br \/>\n<strong>Select all that apply.<\/strong><\/p>\n<ul>\n<li>Aneurysm formation<\/li>\n<li>Clot formation<\/li>\n<li>Decreased blood pressure<\/li>\n<li>Arythmias<\/li>\n<\/ul>\n<p><strong>3. Fill in the blank.<\/strong><\/p>\n<p>As atherosclerosis progresses, _____ can form on the luminal surface of the vessel, exposing underlying layers of the vessel wall.<\/p>\n<p><strong>4. Finish the following sentence. Aneurysm is usually a consequences of a weakened:<\/strong><\/p>\n<ul>\n<li>Tunica intima<\/li>\n<li>Tunica media<\/li>\n<li>Tunica externa<\/li>\n<\/ul>\n<p><strong>5. Fill in the blank.<\/strong><\/p>\n<p>_____ damage is necessary for atherosclerotic lesion initiation.<\/p>\n<p><strong>6. In atherosclerosis, lipid deposits can accumulate in both tunica intima and tunica media.<\/strong><\/p>\n<ul>\n<li>True<\/li>\n<li>False<\/li>\n<\/ul>\n<p><strong>7. Fill in the blank.<\/strong><\/p>\n<p>_____ deposits in advanced atherosclerosis harden the vessel wall and make it brittle.<\/p>\n<p>&nbsp;<\/p>\n<div class=\"textbox\">\n<h2>Answer Key<\/h2>\n<ol>\n<li>Yellow<\/li>\n<li>Aneurysm formation, clot formation<\/li>\n<li>Ulcers<\/li>\n<li>Tunica media<\/li>\n<li>Endothelial<\/li>\n<li>True<\/li>\n<li>Calcium<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_3231_3923\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_3231_3923\"><div tabindex=\"-1\"><p>same as atherosclerotic plaque<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_3231_3893\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_3231_3893\"><div tabindex=\"-1\"><p>elevated blood pressure<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_3231_2208\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_3231_2208\"><div tabindex=\"-1\"><p>(also, tunica interna) innermost lining or tunic of a vessel<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_3231_2209\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_3231_2209\"><div tabindex=\"-1\"><p>middle layer or tunic of a vessel (except capillaries)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_3231_3914\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_3231_3914\"><div tabindex=\"-1\"><p>abnormal ballooning\/ widening of the blood vessel wall cause by it's weakness. Aneurysm rupture is very dangerous and often fatal<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_3231_3862\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_3231_3862\"><div tabindex=\"-1\"><p>lack of oxygen supply to the tissues<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_3231_2100\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_3231_2100\"><div tabindex=\"-1\"><p>branches of the ascending aorta that supply blood to the heart; the left coronary artery feeds the left side of the heart, the left atrium and ventricle, and the interventricular septum; the right coronary artery feeds the right atrium, portions of both ventricles, and the heart conduction system<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_3231_2207\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_3231_2207\"><div tabindex=\"-1\"><p>(also, tunica adventitia) outermost layer or tunic of a vessel (except capillaries)<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><\/div>","protected":false},"author":1232,"menu_order":9,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["tetiana-p"],"pb_section_license":""},"chapter-type":[],"contributor":[104],"license":[],"class_list":["post-3231","chapter","type-chapter","status-publish","hentry","contributor-tetiana-p"],"part":322,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters\/3231","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/users\/1232"}],"version-history":[{"count":25,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters\/3231\/revisions"}],"predecessor-version":[{"id":9840,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters\/3231\/revisions\/9840"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/parts\/322"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters\/3231\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/media?parent=3231"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapter-type?post=3231"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/contributor?post=3231"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/license?post=3231"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}