{"id":645,"date":"2021-07-24T01:15:09","date_gmt":"2021-07-24T05:15:09","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/pathology\/?post_type=chapter&#038;p=645"},"modified":"2025-11-15T18:41:00","modified_gmt":"2025-11-15T23:41:00","slug":"normal-blood-vessel-anatomy-histology","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/pathology\/chapter\/normal-blood-vessel-anatomy-histology\/","title":{"raw":"Gross Anatomy and Histology of Normal Aorta","rendered":"Gross Anatomy and Histology of Normal Aorta"},"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>Compare and contrast the main histological features of tissues that can be identified via H&amp;E and elastic\/trichrome stains.<\/li>\r\n \t<li>Identify three main layers (tunics) in the wall of the aorta and their main components.<\/li>\r\n \t<li>Relate the structural features of aorta to its function.<\/li>\r\n<\/ul>\r\n<\/div>\r\n<\/div>\r\nArteries are blood vessels that transport and distribute oxygenated blood from the heart to all the organs in the body (<em><span style=\"background-color: #ffffff\">with one exception - pulmonary arteries transport deoxygenated blood from the heart to the lungs for gas exchange as a part of pulmonary circle<\/span><\/em>). The <strong>aorta<\/strong>, which originates from the aortic valve in the left ventricle, is the largest artery in the human body. Arteries are responsible for regulating blood pressure, which morphologically translates into a thick smooth muscle layer that facilitates contraction and dilatation in response to physiological stimuli.\r\n\r\nAorta is a unique example of an [pb_glossary id=\"2194\"]elastic artery[\/pb_glossary] and contains a lot of elastic fibers within its wall that allow for a large variation of the [pb_glossary id=\"2198\"]lumen[\/pb_glossary] size.\r\n<div class=\"textbox\">\r\n\r\nOne the <em><strong>gross anatomy<\/strong><\/em> specimen that features [pb_glossary id=\"3777\"]ascending aorta[\/pb_glossary], identify:\r\n<ul>\r\n \t<li>smooth luminal surface, which is required for uninterrupted blood flow;<\/li>\r\n \t<li>wide diameter (around 20-30 mm in [pb_glossary id=\"3777\"]ascending aorta[\/pb_glossary]), necessary for allowing large volumes of oxygenated blood to be conducted from the heart into the vascular tree;<\/li>\r\n \t<li>thick walls (2-3 mm in the ascending aorta), which reflect high blood pressure in the aorta;<\/li>\r\n \t<li>color: aorta appears yellow\/white due to a high amount of connective tissue fibers (collagen, elastin).<\/li>\r\n<\/ul>\r\n<strong>Please note:\u00a0<\/strong>the classic depiction of normal heart anatomy usually examines the heart chambers and vessels from the anterior side. In this gross anatomy specimen, however, the heart chambers and vessels are examined from the posterior side<em><strong>. <\/strong><\/em>Thus, the left ventricle is on the left, and the aorta is in front of the [pb_glossary id=\"2132\"]pulmonary trunk[\/pb_glossary].\r\n\r\n<\/div>\r\n&nbsp;\r\n\r\n[caption id=\"attachment_7868\" align=\"aligncenter\" width=\"1024\"]<img class=\"size-large wp-image-7868\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2024\/12\/Normal-heart-anatomy-figure-1024x576.png\" alt=\"an illustrated heart is opened so all 4 chambers of the heart are visible. The great vessels (pulmonary trunk and aorta) fill the top middle of the image and they are connected to the ventricles taking up the bottom of the image - identifiable by their thick walls. Separating the ventricles from the upper atria are the tricuspid and mitral valves which are attached to the ventricle by thing stands of chordae tendinae\" width=\"1024\" height=\"576\" \/> Normal Heart Anatomy[\/caption]\r\n\r\n&nbsp;\r\n\r\n[caption id=\"attachment_4330\" align=\"aligncenter\" width=\"1024\"]<img class=\"size-large wp-image-4330\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Heart-anatomy-1024x576.png\" alt=\"A pig heart has been opened so that the inner chambers are visible. The left ventricle is on the bottom left with a very thick (2-3cm) wall whereas the right ventricle (bottom right corner) has a thinner wall The ventricles are separated by thin white translucent tissue that make up the mitral and tricuspid valves. Thin white strands of chordae tendinae connect these valves to the papillary muscle nestled in the ventricles. Both the pulmonary trunk and aorta take up the top middle: both are thick white tissue that are thick enough to hold their luminal space open.\" width=\"1024\" height=\"576\" \/> <strong>DHPLC Specimen B0001<\/strong> Normal heart anatomy (pig). <em>All rights reserved<\/em>[\/caption]\r\n<h2>Histology of the Aorta<\/h2>\r\nBefore examining the histological sections of a normal human aorta, it is important to consider commonly used histological stains and their interpretation.\r\nGenerally, the stains are divided into non-specific, the ones that use dyes that stain all the cells within tissue in a similar manner, and special - the ones that use dyes that selectively bind to specific tissue\/cell components.\r\n\r\nThis section will examine the normal histology of the human aorta using histology slides stained with [pb_glossary id=\"393\"]hematoxylin[\/pb_glossary] &amp; [pb_glossary id=\"394\"]eosin[\/pb_glossary] (<em><strong>H&amp;E, non-specific<\/strong><\/em>) and <em><strong>elastin\/trichrome (special)<\/strong><\/em> stains.\r\n\r\nPlease refer to the sections <a href=\"https:\/\/pressbooks.bccampus.ca\/pathology\/chapter\/how-are-the-specimens-obtained-and-prepared\/\">How Are the Specimens Obtained and Prepared?<\/a> and\u00a0<a href=\"https:\/\/pressbooks.bccampus.ca\/pathology\/chapter\/a-demonstrative-videolesson-on-histology\/\">Video Lessons on Histology<\/a> to learn more about the stains and histology slide preparation.\r\n<h3><strong>H&amp;E Stain Interpretation\u00a0<\/strong><\/h3>\r\n[caption id=\"attachment_7872\" align=\"aligncenter\" width=\"1024\"]<img class=\"wp-image-7872 size-full\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/HE-Eosin.png\" alt=\"a microscopic image of skin tissue stained pink (with eosin) and purple (hematoxylin). There are 3 clusters of cells, each surrounding a central opening. The cells are mostly pink with a purple ovoid at the basolateral side of the cell (away from the opening)\" width=\"1024\" height=\"576\" \/> <strong>DHPLC e-slide PATH 304 004<\/strong> Thick Skin Foot. <em>All rights reserved<\/em>[\/caption]\r\n\r\n&nbsp;\r\n\r\n[caption id=\"attachment_3775\" align=\"aligncenter\" width=\"1024\"]<img class=\"size-large wp-image-3775\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Elastin-stain-1024x576.png\" alt=\"microscopic view of the aorta stained blue, black, red, and dark pink. The image looks like multiple parallel waves: the top most being light blue suggesting presence of elastin\/collagen. The lower image shows lots of black and purple (blue +red) suggesting muscle tissue with lots of collagen\" width=\"1024\" height=\"576\" \/> <strong>DHPLC e-slide PATH 304 \u2013 024<\/strong> Elastin\/trichome stain of normal aorta. <em>All rights reserved<\/em>[\/caption]\r\n\r\nTo better understand changes that occur in the blood vessel wall during the development of atherosclerosis, it\u2019s critical to understand the normal histology of large blood vessels.\r\nEven though the morphology of blood vessels of different sizes and types ([pb_glossary id=\"2188\"]arteries[\/pb_glossary], [pb_glossary id=\"2215\"]veins[\/pb_glossary], [pb_glossary id=\"2191\"]capillaries[\/pb_glossary]) exhibits functional adaptations that reflect the location of a blood vessel and local blood pressure, the main features of the blood vessel wall remain the same across various types.\r\n\r\nThe wall of the aorta consists of 3 layers (tunics):\r\n\r\n1. <em><strong>Tunica intima<\/strong><\/em> - thin innermost layer that includes:\r\n\r\na) [pb_glossary id=\"1125\"]Endothelium[\/pb_glossary] - a single layer of epithelial cells that forms the luminal surface of the vessel and is in direct contact with blood. Endothelium within the wall of blood vessels is continuous with the [pb_glossary id=\"2105\"]endocardium[\/pb_glossary] - the inner lining of the heart;\r\n\r\nb) [pb_glossary id=\"3766\"]Loose connective tissue[\/pb_glossary] - a thin layer of connective tissue located under[pb_glossary id=\"1125\"] endothelium[\/pb_glossary]\r\n\r\n2. <em><strong>Tunica media<\/strong><\/em> - the thickest layer in the aorta, includes:\r\n\r\na) Smooth muscle cells that allow for contraction and relaxation;\r\n\r\nb) [pb_glossary id=\"1845\"]Elastin fibers[\/pb_glossary] that further expand the ability of aorta to dilate and contract; in aorta, numerous elastin fibers are located within tunica media, and some within tunica intima;\r\n\r\nc) Connective tissue fibers and nerves.\r\n\r\n3. <em><strong>Tunica adventitia<\/strong><\/em> -the outermost layer that includes:\r\n\r\na) Connective tissue for structural support and protection;\r\n\r\nb) Nerve fascicles ([pb_glossary id=\"2202\"]nervi vasorum[\/pb_glossary]) and blood vessels ([pb_glossary id=\"2210\"]vasa vasorum[\/pb_glossary]) that supply and innervate the wall of the aorta\r\n\r\nAs an elastic artery, aorta contains a large amount of elastic fibers within the tunica media. This amount of elastin allows aorta to expand and recoil in response to blood pressure fluctuations (<em>similarly to how an elastic band behaves<\/em>) and conduct large volumes of blood that's ejected from the heart under high pressure.\r\n\r\nIn addition to being present within tunica media, elastin fibers also form two structures on the border between tunics:\r\n\r\na) Internal elastic lamina - on the border between tunica intima and tunica media;\r\n\r\nb) External elastic lamina - on the border between tunica media and tunica adventitia\r\n\r\nBoth elastic laminas are thick bands of elastin fibers that appear wavy on the histological slide, which reflects the properties of elastin in a relaxed state. Elastic laminas are more easily identified in smaller arteries, where elastin fibers are located only within the laminas. In the aorta, which has numerous elastin fibers within tunica media, elastic laminas would be the fibers on the border between the tunics.\r\n\r\n[h5p id=\"183\"]\r\n<p style=\"background-color: #f0f0f0;padding: 5px;text-align: left\"><sup><em><strong>Normal histology of aorta<\/strong>. Created and presented by Tetiana Povshedna. Histology slides are DHPLC specimens PATH 304-023 (H&amp;E) and PATH 304-024 (elastin\/trichome). Illustrations were created under license with Biorender.com.\u00a0<\/em><\/sup><\/p>\r\n\r\n<h2>Compare and Contrast the Histological Appearance of 3 Tunics in Various Blood Vessel Types<\/h2>\r\n<div class=\"textbox\">\r\n\r\nPlease note the variation in the thickness of tunica media and the amount of elastic fibers between the two large vessels - aorta and vena cava.\r\n\r\nThese morphological adaptations reflect blood vessel location and blood pressure levels - both thickness of tunica media and amount of elastin fibers decrease in veins and venules compared to arteries. Note that [pb_glossary id=\"2209\"]tunica media[\/pb_glossary] is the thickest layer in aorta, but not in vena cava.[pb_glossary id=\"2207\"] Tunica externa[\/pb_glossary] of the [pb_glossary id=\"3779\"]vena cava[\/pb_glossary] is the thickest layer that also contains some smooth muscle fibers.\r\n\r\n<\/div>\r\n<h3><strong>Aorta<\/strong><\/h3>\r\n[caption id=\"attachment_3785\" align=\"aligncenter\" width=\"1024\"]<img class=\"size-large wp-image-3785\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Aorta-Elastin-1024x576.png\" alt=\"layers of the aorta is visible and enumerated with 1 (tunica intima) at the top of the image, 2 (tunica media) which fills up the middle of the image), and 3 (tunica externa) which occupies the bottom. The top 2 tunica stain a dark blue\/black with a background colour of pink, with a sense of parallel layers. The tunica intimal layer show a light blue with discrete layers of cells atop each other. The medial layer is dark blue\/black with pink suggesting a lot of collagen and elastin. The externa has a variety of tissues including fat (all white with no stain), and dark pink with purple nuclei.Elastin\/trichome stain of normal aorta. DHPLC e-slide PATH 304-024\" width=\"1024\" height=\"576\" \/> <strong>DHPLC e-slide PATH 304-024<\/strong>\u00a0Elastin\/trichome stain of normal aorta. <em>All rights reserved<\/em>[\/caption]\r\n<h2><strong>\u00a0<\/strong>Vena Cava<\/h2>\r\n[caption id=\"attachment_3780\" align=\"aligncenter\" width=\"1024\"]<img class=\"size-large wp-image-3780\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-HE-1024x576.png\" alt=\"layers of the vena cava is visible and enumerated with 1 (tunica intima) at the top of the image, 2 (tunica media) which fills up the middle of the image), and 3 (tunica externa) which occupies the bottom. All three tunica stain an intense dark pink. The tunica intima and top half of the media are round clusters, arranged in layers. The bottom half of the tunica media shows long dark pink cells with purple nuclei. The externa has a variety of tissues including fat (all white with no stain), and dark pink with purple nuclei.\" width=\"1024\" height=\"576\" \/> <strong>DHPLC e-slide PATH 304 025<\/strong> H &amp; E stain of vena cava. <em>All rights reserved<\/em>[\/caption]\r\n\r\n&nbsp;\r\n\r\n[caption id=\"attachment_3781\" align=\"aligncenter\" width=\"1024\"]<img class=\"size-large wp-image-3781\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-Elastin-1024x576.png\" alt=\"microscopic analysis of the vena cava, stained for elastin (purple). The vena cava is labelled into the three tunica: intima, media, and externa. The middle tunica media stains a strong purple suggesting a high amount of elastin is present.\" width=\"1024\" height=\"576\" \/> <strong>DHPLC e-slide PATH 304 026<\/strong> Elastin\/trichrome stain of vena cava<em>. All rights reserved<\/em>[\/caption]\r\n<h2>Section Review<\/h2>\r\n<span style=\"background-color: #ffffff\">Blood vessels across the vascular tree share a similar histological structure - their wall consists of three layers (also known as tunics). The thickness and characteristics of these layers ([pb_glossary id=\"2208\"]tunica intima[\/pb_glossary], [pb_glossary id=\"2209\"]tunica media[\/pb_glossary], [pb_glossary id=\"2207\"]tunica externa[\/pb_glossary]) vary depending on the blood vessel type (<em>artery vs vein<\/em>) and location (<em>closer or further from the heart<\/em>). Aorta, a major vessel that carries oxygenated blood from the heart and distributes it to organs and tissues, is an [pb_glossary id=\"2194\"]elastic artery[\/pb_glossary] that contains numerous elastic fibers across the layers, with the majority of them accumulated within the middle muscular layer (tunica media). This histological feature allows aorta to expand and recoil in response to blood pressure fluctuations, and carry large amounts of oxygenated blood from the heart.\u00a0<\/span>\r\n\r\n&nbsp;\r\n<h1>Review Questions<\/h1>\r\n<div class=\"h5p\">[h5p id=\"190\"]<\/div>\r\n<div class=\"pdf\">\r\n\r\n<strong>1. Fill in the blanks. <\/strong>Aorta is the largest artery in the human body that carries _____ blood from the heart to tissues and organs.\r\n\r\n<strong>2. Finish the following sentence. The wall of human aorta consists of three layers (also known as tunics):<\/strong>\r\n<strong>Select all that apply.<\/strong>\r\n<ul>\r\n \t<li>Tunica interna<\/li>\r\n \t<li>Tunica media<\/li>\r\n \t<li>Tunica intermedialis<\/li>\r\n \t<li>Tunica extra<\/li>\r\n<\/ul>\r\n<strong>3. Generally, blood vessels of various types and sizes share a common histological structure.<\/strong>\r\n<ul>\r\n \t<li>True<\/li>\r\n \t<li>False<\/li>\r\n<\/ul>\r\n<strong>4. Fill in the blanks.<\/strong>\r\n\r\nTunica _____ is the thickest layer in aorta, while tunica _____ is the thickest layer in vena cava.\r\n\r\n<strong>5. Finish the following sentence. Large amount of elastic fibers in the tunica media of aorta allows for:<\/strong>\r\n<strong>Select all that apply.<\/strong>\r\n<ul>\r\n \t<li>Dilation and contraction in response to blood pressure and fluctuations<\/li>\r\n \t<li>Variability of lumen size depending on physiological conditions<\/li>\r\n \t<li>Transport the large volumes of oxygenated blood outside the heart<\/li>\r\n \t<li>Blood pressure regulation<\/li>\r\n \t<li>Pulse variability<\/li>\r\n<\/ul>\r\n&nbsp;\r\n<div class=\"textbox\">\r\n<h2>Answer Key<\/h2>\r\n<ol>\r\n \t<li>Oxygenated<\/li>\r\n \t<li>Tunica interna, tunica externa, tunica media<\/li>\r\n \t<li>True<\/li>\r\n \t<li>Media, tunica, externa<\/li>\r\n \t<li>Dilation and contraction in response to blood pressure fluctuations, variability of lumen size depending on physiological conditions, transport of large volumes of oxygenated blood outside of heart<\/li>\r\n<\/ol>\r\n<\/div>\r\n<\/div>\r\n&nbsp;","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>Compare and contrast the main histological features of tissues that can be identified via H&amp;E and elastic\/trichrome stains.<\/li>\n<li>Identify three main layers (tunics) in the wall of the aorta and their main components.<\/li>\n<li>Relate the structural features of aorta to its function.<\/li>\n<\/ul>\n<\/div>\n<\/div>\n<p>Arteries are blood vessels that transport and distribute oxygenated blood from the heart to all the organs in the body (<em><span style=\"background-color: #ffffff\">with one exception &#8211; pulmonary arteries transport deoxygenated blood from the heart to the lungs for gas exchange as a part of pulmonary circle<\/span><\/em>). The <strong>aorta<\/strong>, which originates from the aortic valve in the left ventricle, is the largest artery in the human body. Arteries are responsible for regulating blood pressure, which morphologically translates into a thick smooth muscle layer that facilitates contraction and dilatation in response to physiological stimuli.<\/p>\n<p>Aorta is a unique example of an <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2194\">elastic artery<\/a> and contains a lot of elastic fibers within its wall that allow for a large variation of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2198\">lumen<\/a> size.<\/p>\n<div class=\"textbox\">\n<p>One the <em><strong>gross anatomy<\/strong><\/em> specimen that features <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_3777\">ascending aorta<\/a>, identify:<\/p>\n<ul>\n<li>smooth luminal surface, which is required for uninterrupted blood flow;<\/li>\n<li>wide diameter (around 20-30 mm in <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_3777\">ascending aorta<\/a>), necessary for allowing large volumes of oxygenated blood to be conducted from the heart into the vascular tree;<\/li>\n<li>thick walls (2-3 mm in the ascending aorta), which reflect high blood pressure in the aorta;<\/li>\n<li>color: aorta appears yellow\/white due to a high amount of connective tissue fibers (collagen, elastin).<\/li>\n<\/ul>\n<p><strong>Please note:\u00a0<\/strong>the classic depiction of normal heart anatomy usually examines the heart chambers and vessels from the anterior side. In this gross anatomy specimen, however, the heart chambers and vessels are examined from the posterior side<em><strong>. <\/strong><\/em>Thus, the left ventricle is on the left, and the aorta is in front of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2132\">pulmonary trunk<\/a>.<\/p>\n<\/div>\n<p>&nbsp;<\/p>\n<figure id=\"attachment_7868\" aria-describedby=\"caption-attachment-7868\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-7868\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2024\/12\/Normal-heart-anatomy-figure-1024x576.png\" alt=\"an illustrated heart is opened so all 4 chambers of the heart are visible. The great vessels (pulmonary trunk and aorta) fill the top middle of the image and they are connected to the ventricles taking up the bottom of the image - identifiable by their thick walls. Separating the ventricles from the upper atria are the tricuspid and mitral valves which are attached to the ventricle by thing stands of chordae tendinae\" width=\"1024\" height=\"576\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2024\/12\/Normal-heart-anatomy-figure-1024x576.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2024\/12\/Normal-heart-anatomy-figure-300x169.png 300w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2024\/12\/Normal-heart-anatomy-figure-768x432.png 768w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2024\/12\/Normal-heart-anatomy-figure-65x37.png 65w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2024\/12\/Normal-heart-anatomy-figure-225x127.png 225w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2024\/12\/Normal-heart-anatomy-figure-350x197.png 350w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2024\/12\/Normal-heart-anatomy-figure.png 1280w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption id=\"caption-attachment-7868\" class=\"wp-caption-text\">Normal Heart Anatomy<\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<figure id=\"attachment_4330\" aria-describedby=\"caption-attachment-4330\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-4330\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Heart-anatomy-1024x576.png\" alt=\"A pig heart has been opened so that the inner chambers are visible. The left ventricle is on the bottom left with a very thick (2-3cm) wall whereas the right ventricle (bottom right corner) has a thinner wall The ventricles are separated by thin white translucent tissue that make up the mitral and tricuspid valves. Thin white strands of chordae tendinae connect these valves to the papillary muscle nestled in the ventricles. Both the pulmonary trunk and aorta take up the top middle: both are thick white tissue that are thick enough to hold their luminal space open.\" width=\"1024\" height=\"576\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Heart-anatomy-1024x576.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Heart-anatomy-300x169.png 300w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Heart-anatomy-768x432.png 768w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Heart-anatomy-65x37.png 65w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Heart-anatomy-225x127.png 225w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Heart-anatomy-350x197.png 350w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Heart-anatomy.png 1280w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption id=\"caption-attachment-4330\" class=\"wp-caption-text\"><strong>DHPLC Specimen B0001<\/strong> Normal heart anatomy (pig). <em>All rights reserved<\/em><\/figcaption><\/figure>\n<h2>Histology of the Aorta<\/h2>\n<p>Before examining the histological sections of a normal human aorta, it is important to consider commonly used histological stains and their interpretation.<br \/>\nGenerally, the stains are divided into non-specific, the ones that use dyes that stain all the cells within tissue in a similar manner, and special &#8211; the ones that use dyes that selectively bind to specific tissue\/cell components.<\/p>\n<p>This section will examine the normal histology of the human aorta using histology slides stained with <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_393\">hematoxylin<\/a> &amp; <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_394\">eosin<\/a> (<em><strong>H&amp;E, non-specific<\/strong><\/em>) and <em><strong>elastin\/trichrome (special)<\/strong><\/em> stains.<\/p>\n<p>Please refer to the sections <a href=\"https:\/\/pressbooks.bccampus.ca\/pathology\/chapter\/how-are-the-specimens-obtained-and-prepared\/\">How Are the Specimens Obtained and Prepared?<\/a> and\u00a0<a href=\"https:\/\/pressbooks.bccampus.ca\/pathology\/chapter\/a-demonstrative-videolesson-on-histology\/\">Video Lessons on Histology<\/a> to learn more about the stains and histology slide preparation.<\/p>\n<h3><strong>H&amp;E Stain Interpretation\u00a0<\/strong><\/h3>\n<figure id=\"attachment_7872\" aria-describedby=\"caption-attachment-7872\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-7872 size-full\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/HE-Eosin.png\" alt=\"a microscopic image of skin tissue stained pink (with eosin) and purple (hematoxylin). There are 3 clusters of cells, each surrounding a central opening. The cells are mostly pink with a purple ovoid at the basolateral side of the cell (away from the opening)\" width=\"1024\" height=\"576\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/HE-Eosin.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/HE-Eosin-300x169.png 300w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/HE-Eosin-768x432.png 768w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/HE-Eosin-65x37.png 65w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/HE-Eosin-225x127.png 225w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/HE-Eosin-350x197.png 350w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption id=\"caption-attachment-7872\" class=\"wp-caption-text\"><strong>DHPLC e-slide PATH 304 004<\/strong> Thick Skin Foot. <em>All rights reserved<\/em><\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<figure id=\"attachment_3775\" aria-describedby=\"caption-attachment-3775\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-3775\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Elastin-stain-1024x576.png\" alt=\"microscopic view of the aorta stained blue, black, red, and dark pink. The image looks like multiple parallel waves: the top most being light blue suggesting presence of elastin\/collagen. The lower image shows lots of black and purple (blue +red) suggesting muscle tissue with lots of collagen\" width=\"1024\" height=\"576\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Elastin-stain-1024x576.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Elastin-stain-300x169.png 300w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Elastin-stain-768x432.png 768w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Elastin-stain-65x37.png 65w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Elastin-stain-225x127.png 225w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Elastin-stain-350x197.png 350w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Elastin-stain.png 1280w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption id=\"caption-attachment-3775\" class=\"wp-caption-text\"><strong>DHPLC e-slide PATH 304 \u2013 024<\/strong> Elastin\/trichome stain of normal aorta. <em>All rights reserved<\/em><\/figcaption><\/figure>\n<p>To better understand changes that occur in the blood vessel wall during the development of atherosclerosis, it\u2019s critical to understand the normal histology of large blood vessels.<br \/>\nEven though the morphology of blood vessels of different sizes and types (<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2188\">arteries<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2215\">veins<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2191\">capillaries<\/a>) exhibits functional adaptations that reflect the location of a blood vessel and local blood pressure, the main features of the blood vessel wall remain the same across various types.<\/p>\n<p>The wall of the aorta consists of 3 layers (tunics):<\/p>\n<p>1. <em><strong>Tunica intima<\/strong><\/em> &#8211; thin innermost layer that includes:<\/p>\n<p>a) <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_1125\">Endothelium<\/a> &#8211; a single layer of epithelial cells that forms the luminal surface of the vessel and is in direct contact with blood. Endothelium within the wall of blood vessels is continuous with the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2105\">endocardium<\/a> &#8211; the inner lining of the heart;<\/p>\n<p>b) <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_3766\">Loose connective tissue<\/a> &#8211; a thin layer of connective tissue located under<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_1125\"> endothelium<\/a><\/p>\n<p>2. <em><strong>Tunica media<\/strong><\/em> &#8211; the thickest layer in the aorta, includes:<\/p>\n<p>a) Smooth muscle cells that allow for contraction and relaxation;<\/p>\n<p>b) <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_1845\">Elastin fibers<\/a> that further expand the ability of aorta to dilate and contract; in aorta, numerous elastin fibers are located within tunica media, and some within tunica intima;<\/p>\n<p>c) Connective tissue fibers and nerves.<\/p>\n<p>3. <em><strong>Tunica adventitia<\/strong><\/em> -the outermost layer that includes:<\/p>\n<p>a) Connective tissue for structural support and protection;<\/p>\n<p>b) Nerve fascicles (<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2202\">nervi vasorum<\/a>) and blood vessels (<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2210\">vasa vasorum<\/a>) that supply and innervate the wall of the aorta<\/p>\n<p>As an elastic artery, aorta contains a large amount of elastic fibers within the tunica media. This amount of elastin allows aorta to expand and recoil in response to blood pressure fluctuations (<em>similarly to how an elastic band behaves<\/em>) and conduct large volumes of blood that&#8217;s ejected from the heart under high pressure.<\/p>\n<p>In addition to being present within tunica media, elastin fibers also form two structures on the border between tunics:<\/p>\n<p>a) Internal elastic lamina &#8211; on the border between tunica intima and tunica media;<\/p>\n<p>b) External elastic lamina &#8211; on the border between tunica media and tunica adventitia<\/p>\n<p>Both elastic laminas are thick bands of elastin fibers that appear wavy on the histological slide, which reflects the properties of elastin in a relaxed state. Elastic laminas are more easily identified in smaller arteries, where elastin fibers are located only within the laminas. In the aorta, which has numerous elastin fibers within tunica media, elastic laminas would be the fibers on the border between the tunics.<\/p>\n<div id=\"h5p-183\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-183\" class=\"h5p-iframe\" data-content-id=\"183\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Normal histology of human aorta\"><\/iframe><\/div>\n<\/div>\n<p style=\"background-color: #f0f0f0;padding: 5px;text-align: left\"><sup><em><strong>Normal histology of aorta<\/strong>. Created and presented by Tetiana Povshedna. Histology slides are DHPLC specimens PATH 304-023 (H&amp;E) and PATH 304-024 (elastin\/trichome). Illustrations were created under license with Biorender.com.\u00a0<\/em><\/sup><\/p>\n<h2>Compare and Contrast the Histological Appearance of 3 Tunics in Various Blood Vessel Types<\/h2>\n<div class=\"textbox\">\n<p>Please note the variation in the thickness of tunica media and the amount of elastic fibers between the two large vessels &#8211; aorta and vena cava.<\/p>\n<p>These morphological adaptations reflect blood vessel location and blood pressure levels &#8211; both thickness of tunica media and amount of elastin fibers decrease in veins and venules compared to arteries. Note that <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2209\">tunica media<\/a> is the thickest layer in aorta, but not in vena cava.<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2207\"> Tunica externa<\/a> of the <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_3779\">vena cava<\/a> is the thickest layer that also contains some smooth muscle fibers.<\/p>\n<\/div>\n<h3><strong>Aorta<\/strong><\/h3>\n<figure id=\"attachment_3785\" aria-describedby=\"caption-attachment-3785\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-3785\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Aorta-Elastin-1024x576.png\" alt=\"layers of the aorta is visible and enumerated with 1 (tunica intima) at the top of the image, 2 (tunica media) which fills up the middle of the image), and 3 (tunica externa) which occupies the bottom. The top 2 tunica stain a dark blue\/black with a background colour of pink, with a sense of parallel layers. The tunica intimal layer show a light blue with discrete layers of cells atop each other. The medial layer is dark blue\/black with pink suggesting a lot of collagen and elastin. The externa has a variety of tissues including fat (all white with no stain), and dark pink with purple nuclei.Elastin\/trichome stain of normal aorta. DHPLC e-slide PATH 304-024\" width=\"1024\" height=\"576\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Aorta-Elastin-1024x576.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Aorta-Elastin-300x169.png 300w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Aorta-Elastin-768x432.png 768w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Aorta-Elastin-65x37.png 65w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Aorta-Elastin-225x127.png 225w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Aorta-Elastin-350x197.png 350w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Aorta-Elastin.png 1280w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption id=\"caption-attachment-3785\" class=\"wp-caption-text\"><strong>DHPLC e-slide PATH 304-024<\/strong>\u00a0Elastin\/trichome stain of normal aorta. <em>All rights reserved<\/em><\/figcaption><\/figure>\n<h2><strong>\u00a0<\/strong>Vena Cava<\/h2>\n<figure id=\"attachment_3780\" aria-describedby=\"caption-attachment-3780\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-3780\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-HE-1024x576.png\" alt=\"layers of the vena cava is visible and enumerated with 1 (tunica intima) at the top of the image, 2 (tunica media) which fills up the middle of the image), and 3 (tunica externa) which occupies the bottom. All three tunica stain an intense dark pink. The tunica intima and top half of the media are round clusters, arranged in layers. The bottom half of the tunica media shows long dark pink cells with purple nuclei. The externa has a variety of tissues including fat (all white with no stain), and dark pink with purple nuclei.\" width=\"1024\" height=\"576\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-HE-1024x576.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-HE-300x169.png 300w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-HE-768x432.png 768w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-HE-65x37.png 65w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-HE-225x127.png 225w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-HE-350x197.png 350w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-HE.png 1280w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption id=\"caption-attachment-3780\" class=\"wp-caption-text\"><strong>DHPLC e-slide PATH 304 025<\/strong> H &amp; E stain of vena cava. <em>All rights reserved<\/em><\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<figure id=\"attachment_3781\" aria-describedby=\"caption-attachment-3781\" style=\"width: 1024px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"size-large wp-image-3781\" src=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-Elastin-1024x576.png\" alt=\"microscopic analysis of the vena cava, stained for elastin (purple). The vena cava is labelled into the three tunica: intima, media, and externa. The middle tunica media stains a strong purple suggesting a high amount of elastin is present.\" width=\"1024\" height=\"576\" srcset=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-Elastin-1024x576.png 1024w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-Elastin-300x169.png 300w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-Elastin-768x432.png 768w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-Elastin-65x37.png 65w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-Elastin-225x127.png 225w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-Elastin-350x197.png 350w, https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-Elastin.png 1280w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><figcaption id=\"caption-attachment-3781\" class=\"wp-caption-text\"><strong>DHPLC e-slide PATH 304 026<\/strong> Elastin\/trichrome stain of vena cava<em>. All rights reserved<\/em><\/figcaption><\/figure>\n<h2>Section Review<\/h2>\n<p><span style=\"background-color: #ffffff\">Blood vessels across the vascular tree share a similar histological structure &#8211; their wall consists of three layers (also known as tunics). The thickness and characteristics of these layers (<a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2208\">tunica intima<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2209\">tunica media<\/a>, <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2207\">tunica externa<\/a>) vary depending on the blood vessel type (<em>artery vs vein<\/em>) and location (<em>closer or further from the heart<\/em>). Aorta, a major vessel that carries oxygenated blood from the heart and distributes it to organs and tissues, is an <a class=\"glossary-term\" aria-haspopup=\"dialog\" aria-describedby=\"definition\" href=\"#term_645_2194\">elastic artery<\/a> that contains numerous elastic fibers across the layers, with the majority of them accumulated within the middle muscular layer (tunica media). This histological feature allows aorta to expand and recoil in response to blood pressure fluctuations, and carry large amounts of oxygenated blood from the heart.\u00a0<\/span><\/p>\n<p>&nbsp;<\/p>\n<h1>Review Questions<\/h1>\n<div class=\"h5p\">\n<div id=\"h5p-190\">\n<div class=\"h5p-iframe-wrapper\"><iframe id=\"h5p-iframe-190\" class=\"h5p-iframe\" data-content-id=\"190\" style=\"height:1px\" src=\"about:blank\" frameBorder=\"0\" scrolling=\"no\" title=\"Gross anatomy and histology of human aorta\"><\/iframe><\/div>\n<\/div>\n<\/div>\n<div class=\"pdf\">\n<p><strong>1. Fill in the blanks. <\/strong>Aorta is the largest artery in the human body that carries _____ blood from the heart to tissues and organs.<\/p>\n<p><strong>2. Finish the following sentence. The wall of human aorta consists of three layers (also known as tunics):<\/strong><br \/>\n<strong>Select all that apply.<\/strong><\/p>\n<ul>\n<li>Tunica interna<\/li>\n<li>Tunica media<\/li>\n<li>Tunica intermedialis<\/li>\n<li>Tunica extra<\/li>\n<\/ul>\n<p><strong>3. Generally, blood vessels of various types and sizes share a common histological structure.<\/strong><\/p>\n<ul>\n<li>True<\/li>\n<li>False<\/li>\n<\/ul>\n<p><strong>4. Fill in the blanks.<\/strong><\/p>\n<p>Tunica _____ is the thickest layer in aorta, while tunica _____ is the thickest layer in vena cava.<\/p>\n<p><strong>5. Finish the following sentence. Large amount of elastic fibers in the tunica media of aorta allows for:<\/strong><br \/>\n<strong>Select all that apply.<\/strong><\/p>\n<ul>\n<li>Dilation and contraction in response to blood pressure and fluctuations<\/li>\n<li>Variability of lumen size depending on physiological conditions<\/li>\n<li>Transport the large volumes of oxygenated blood outside the heart<\/li>\n<li>Blood pressure regulation<\/li>\n<li>Pulse variability<\/li>\n<\/ul>\n<p>&nbsp;<\/p>\n<div class=\"textbox\">\n<h2>Answer Key<\/h2>\n<ol>\n<li>Oxygenated<\/li>\n<li>Tunica interna, tunica externa, tunica media<\/li>\n<li>True<\/li>\n<li>Media, tunica, externa<\/li>\n<li>Dilation and contraction in response to blood pressure fluctuations, variability of lumen size depending on physiological conditions, transport of large volumes of oxygenated blood outside of heart<\/li>\n<\/ol>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<div class=\"media-attributions clear\" prefix:cc=\"http:\/\/creativecommons.org\/ns#\" prefix:dc=\"http:\/\/purl.org\/dc\/terms\/\"><h2>Media Attributions<\/h2><ul><li about=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2024\/12\/Normal-heart-anatomy-figure.png\"><a rel=\"cc:attributionURL\" href=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2024\/12\/Normal-heart-anatomy-figure.png\" property=\"dc:title\">Normal-heart-anatomy-figure2<\/a>  &copy;  Tetiana Povshedna    is licensed under a  <a rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY (Attribution)<\/a> license<\/li><li about=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Heart-anatomy-1024x576.png\"><a rel=\"cc:attributionURL\" href=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Heart-anatomy-1024x576.png\" property=\"dc:title\">Heart anatomy<\/a>  &copy;  DHPLC    is licensed under a  <a rel=\"license\" href=\"https:\/\/choosealicense.com\/no-license\/\">All Rights Reserved<\/a> license<\/li><li about=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/HE-Eosin.png\"><a rel=\"cc:attributionURL\" href=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/HE-Eosin.png\" property=\"dc:title\">HE Eosin<\/a>    adapted by  Tetiana Povshedna  is licensed under a  <a rel=\"license\" href=\"https:\/\/choosealicense.com\/no-license\/\">All Rights Reserved<\/a> license<\/li><li about=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Elastin-stain-1024x576.png\"><a rel=\"cc:attributionURL\" href=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Elastin-stain-1024x576.png\" property=\"dc:title\">Elastin stain interpretation<\/a>  &copy;  DHPLC  adapted by  Tetiana Povshedna  is licensed under a  <a rel=\"license\" href=\"https:\/\/choosealicense.com\/no-license\/\">All Rights Reserved<\/a> license<\/li><li about=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Aorta-Elastin-1024x576.png\"><a rel=\"cc:attributionURL\" href=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Aorta-Elastin-1024x576.png\" property=\"dc:title\">Aorta Elastin<\/a>  &copy;  DHPLC  adapted by  Tatiana Povshedna  is licensed under a  <a rel=\"license\" href=\"https:\/\/choosealicense.com\/no-license\/\">All Rights Reserved<\/a> license<\/li><li about=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-HE-1024x576.png\"><a rel=\"cc:attributionURL\" href=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-HE-1024x576.png\" property=\"dc:title\">Vena Cava H&amp;E<\/a>  &copy;  DHPLC  adapted by  Tatiana Povshedna  is licensed under a  <a rel=\"license\" href=\"https:\/\/choosealicense.com\/no-license\/\">All Rights Reserved<\/a> license<\/li><li about=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-Elastin-1024x576.png\"><a rel=\"cc:attributionURL\" href=\"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-content\/uploads\/sites\/1260\/2021\/07\/Vena-Cava-Elastin-1024x576.png\" property=\"dc:title\">Vena Cava Elastin<\/a>  &copy;  DHPL  adapted by  Tetiana Povshedna  is licensed under a  <a rel=\"license\" href=\"https:\/\/choosealicense.com\/no-license\/\">All Rights Reserved<\/a> license<\/li><\/ul><\/div><div class=\"glossary\"><span class=\"screen-reader-text\" id=\"definition\">definition<\/span><template id=\"term_645_2194\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_2194\"><div tabindex=\"-1\"><p>(also, conducting artery) artery with abundant elastic fibers located closer to the heart, which maintains the pressure gradient and conducts blood to smaller branches<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_2198\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_2198\"><div tabindex=\"-1\"><p>interior of a tubular structure such as a blood vessel or a portion of the alimentary canal through which blood, chyme, or other substances travel<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_3777\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_3777\"><div tabindex=\"-1\"><p>part of the aorta that originates from the heart; total length - around 5 cm<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_2132\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_2132\"><div tabindex=\"-1\"><p>large arterial vessel that carries blood ejected from the right ventricle; divides into the left and right pulmonary arteries<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_393\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_393\"><div tabindex=\"-1\"><p>A blue basic dye that is used to stain tissues. It turns acidic elements such as RNA and DNA in the tissue blue. <\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_394\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_394\"><div tabindex=\"-1\"><p>Eosin is a pink acidic dye that stains basic elements such as most proteins in the tissue pink or red<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_2188\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_2188\"><div tabindex=\"-1\"><p>blood vessel that conducts blood away from the heart; may be a conducting or distributing 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_645_2215\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_2215\"><div tabindex=\"-1\"><p>blood vessel that conducts blood toward the heart<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_2191\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_2191\"><div tabindex=\"-1\"><p>smallest of blood vessels where physical exchange occurs between the blood and tissue cells surrounded by interstitial fluid<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_1125\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_1125\"><div tabindex=\"-1\"><p>Tissue that lines vessels of the lymphatic and cardiovascular system, made up of a simple squamous epithelium.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_2105\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_2105\"><div tabindex=\"-1\"><p>innermost layer of the heart lining the heart chambers and heart valves; composed of endothelium reinforced with a thin layer of connective tissue that binds to the myocardium<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_3766\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_3766\"><div tabindex=\"-1\"><p>a type of connective tissue that consists of fibroblasts, a large amount of extracellular matrix (also called ground substance), and space connective tissue fibers (collagen, elastin). Loose connective tissue often contains cappillaries, arterioles, and venules that supply epithelium on top of it <\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_1845\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_1845\"><div tabindex=\"-1\"><p>Fibers made of the protein elastin that increase the elasticity of the dermis.<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_2202\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_2202\"><div tabindex=\"-1\"><p>small nerve fibers found in arteries and veins that trigger contraction of the smooth muscle in their walls<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_2210\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_2210\"><div tabindex=\"-1\"><p>small blood vessels located within the walls or tunics of larger vessels that supply nourishment to and remove wastes from the cells of the vessels<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_2209\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_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_645_2207\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_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><template id=\"term_645_3779\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_3779\"><div tabindex=\"-1\"><p>large vein that brings deoxygenated blood from the organs in the body back to the heart<\/p>\n<\/div><button><span aria-hidden=\"true\">&times;<\/span><span class=\"screen-reader-text\">Close definition<\/span><\/button><\/div><\/template><template id=\"term_645_2208\"><div class=\"glossary__definition\" role=\"dialog\" data-id=\"term_645_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><\/div>","protected":false},"author":1232,"menu_order":5,"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-645","chapter","type-chapter","status-publish","hentry","contributor-tetiana-p"],"part":322,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters\/645","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\/645\/revisions"}],"predecessor-version":[{"id":9366,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapters\/645\/revisions\/9366"}],"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\/645\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/media?parent=645"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/pressbooks\/v2\/chapter-type?post=645"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/contributor?post=645"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/pathology\/wp-json\/wp\/v2\/license?post=645"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}