Reading: RR&K, Chapter 12
SLIDE 13a cardiac muscle, human (Masson)
(RR&K p321, Fig.1,2,3)
This slide is a section through the wall of the ventricle of the human heart. The epicardium (visceral pericardium) consists of a thin layer of mesothelial cells on the outer surface of the heart adjacent to a thick layer of subpericardial adipose tissue. Find branches of coronary arteries which supply blood to the heart: these are located in the subpericardial adipose tissue.
Next, locate the endocardium on the luminal surface of the heart. Observe that the endocardium covers surface of papillary muscles. It is composed of 1) an inner layer of simple squamous epithelium (endothelium) and a small amount of subendothelial connective tissue; 2) a middle layer of connective tissue and smooth muscle cells; and 3) subendacardial layer which contains Purkinje fibers. On your slide only inner layer of the endocardium can be identify. The middle principal component of the ventricular wall is the myocardium. It contains the cardiac myocytes (muscle cells), blood vessels and connective tissue.
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SLIDE 13d cardiac muscle, human (H&E)
(RR&K p321, Fig.1,2,3)
This slide is a section through the wall of the ventricle of the human heart. The epicardium is not evident on this slide. Locate once again the endocardium, which is composed of 1) an inner layer of simple squamous epithelium (endothelium) and a small amount of subendothelial connective tissue; 2) a middle layer of connective tissue and smooth muscle cells (difficult to observe on your slide); 3) subendacardial layer which contains Purkinje fibers. These cells are cardiac muscle cells specialized in conducting an electrical impulse. Purkinje cells are larger than the cardiac fiber and contain large amounts of glycogen (unstained regions in the cytoplasm). The central portion of the ventricle wall is the myocardium, which contains the cardiac myocytes (muscle cells), connective tissue with collagen fibers as well as a delicate arrangement of elastic and reticular fibers. Blood vessels can be also found in the myocardium. Epicardium is not visible on this slide.
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SLIDE 11a aorta, human (H&E)
(RR&K p323, Fig.1,2,3,4,5,6)
First, on the low magnification find the luminal surface of the aorta (tunica intima), outer surface of the aorta (tunica adventitia), and the thickest part of the wall (tunica media). The tunica intima consists of the endothe-lium and underlying tissue. The endothelial lining of the intima may be partially detached from the media. Adjacent to the endothelium is the subendothelial layer, composed mainly of fine elastic fibers and collagen fibers. Part of this deeper layer contains thicker elastic and collagen fibers and smooth muscle cells. It does not always form a continuous layer around the aorta. The internal elastic membrane is not very distinctive, but it can usually be equated with the first elastic membrane of the media. The tunica media consists solely of smooth muscle cells. Note the appearance and arrangement of the fenestrated elastic laminae among the collagen fibers and smooth muscle cells. The outermost elastic lamina separates the tunica media from the adventitia and is called the external elastic lamia.
The tunica adventitia is connective tissue and supports the nervi and vasa vasorum. This layer is the best preserved on this slide. Nerves and blood vessels (nervi and vasa vasorum) are located near the media. The adventitia has no clearly defined outer limit since it gradually blends with the surrounding connective and adipose tissue. Can you determine the orientation of your section with respect to the axis of the vessel from which it was cut?
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SLIDE 11c aorta, human (Verhoeff)
(RR&K p323, Fig.1,2,3,4,5,6)
After identifying the tunica intima, media, and adventitia, identify the same elements of the aortic wall on the section stained with Verhoeff stain. Identify the tunica intima. The internal elastic membrane on the aorta is represented by the first elastic membrane of the media. The most prominent feature of this elastic artery is the tunica media with black stained elastic fibers. What cells are synthesizing the elastic fibers? Note the appearance and arrangement of the fenestrated elastic laminae among the collagen fibers and smooth muscle cells, which stain yellow on this slide. The outermost elastic lamina separates the tunica media from the adventitia and is called the external elastic lamia. The tunica adventitia contains primarily collagen fibers which stain pink in this preparation. Nerves and blood vessels (nervi and vasa vasorum) are located near the media. The adventitia has no clearly defined outer limit since it gradually blends with the surrounding adipose and connective tissue.
Check list for SLIDE 11c: 
SLIDE 10a blood vessels, goat (H&E)
(RR&K p325, Fig.1,2,3)
These sections exhibit a cross-section of a neurovascular bundle. The major vessels are represented here by a medium size muscular artery and accompanying vein. As you examine the slide with the inverted ocular, the artery will be the round structure with a thick wall, while the vein will be an irregularly shaped vessel with a thinner wall. Examine the tunica intima, media, and adventia of the large artery and vein. As a result of contraction, the tunica intima (with endothelium and inner elastic lamina) is typically thrown into deep folds, and the nuclei of the endothelial cells protrude into the vessel lumen. The tunica media, consists of densely packed smooth muscle cells with traces of collagen and elastic fibers. It ends with a wide external elastic lamina. Compare the thicknesses of the tunica media of the artery with that of the vein. Tunica adventitia contains collagen and elastic fibers as well as adipose tissue. In the artery, the adventitia layer is smaller than the media. In the vein, the adventitia layer is larger that the media. Small nerves and blood vessels are also located in the tunica adventitia. Arterioles and venules occur throughout the adventitia, often in pairs of one arteriole and one venule. Compare size, wall thickness, amount of smooth muscle, and elastic material in arterioles and venules. Arterioles have 2-4 layers of smooth muscle, while the venule will have only 1-2 layers. Arterioles are easily identified on the slide stained for elastic fibers by the presence of the internal elastic membrane. You will need the high dry or oil immersion objective lens, and you will have to examine several vessels before finding a convincing inner elastic lamina. Compare the structure and size of capillaries with the arterioles and venules. Review the histology of nerve.
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SLIDE 56c small intestine, rat (toluidine blue)
(RR&K p487, Fig.1,2,3)
The core of intestinal villi, which are finger-like projections into the lumen of the small intestine, contains centrally located single lacteal (lymphatic capillary). A few small lymphocytes may be visible within the lymphatic vessels. Compare the thin wall of a lacteal with small blood vessels on this slide. Also find the lymphatic vessels that are present within the submucosa and compare them to venules and arterioles.
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SLIDE 11m aorta, atherosclerosis (Masson)
(RR&K p323, Fig.1,2,3,4,5,6)
Atherosclerosis is a vascular disease characterized by thickening and loss of elasticity of arterial walls. It is a slow, progressive disease of large and medium- sized arteries characterized by the formation of atherosclerotic plaques. Your slide has a section through an atherosclerotic plaque in the aorta stained with Masson. Note that the luminal surface is ruptured above the plaque. The thickest part of the aortic wall is the tunica intima, where you can find elongated smooth muscle cells and large macrophages (known as foam cells because of the lipid droplets that they contain in the cytoplasm). The lipid stains yellow in this preparation. Much of the intima stains green due to the presence of collagen. In addition to the collagen, this area lacks cytological organization and contains mainly cholesterol and its esters, cellular debris, fibrin, and plasma proteins embedded between few elastic and collagen fibers. Aorta plaque formation leads to several complications like ulceration, mural thrombus formation, infarctions, emboli and rupture. The weakness of the tunica media may result in an aneurism. Compare this section with the normal aorta (SLIDE 11b). Identify the tunica media in both slides and compare their differences. Are there any significant changes in the adventitia?
Check list for SLIDE 11m:
The cardiovascular system delivers important substances to the cells, such as nutrients, antibodies, and hormones. It also helps remove wastes produced by cellular processes. This unit examines the basic structure of the cardiovascular system.