Changes

== Smooth Muscle ==

On slide 31, Ileum (H&E), identify smooth muscle fibers in the relatively thick muscle coat (muscularis). The muscle fibers are arranged in two well-defined layers: An inner circular and an outer longitudinal. Between the two layers of muscle is a thin layer of connective tissue that varies in thickness and contains a plexus of nerve fibers and also parasympathetic ganglion cells known as the myenteric plexus (of Auerbach).

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On slide 121, Urinary bladder (H&E), notice how the smooth muscle fibers of the thick muscle coat are arranged as interlacing bundles. Each bundle is supported by moderately dense connective tissue. The arrangement increases the efficiency of expelling urine quickly as well as increases the ability of the organ to withstand the force of distension as urine accumulates within the bladder.

[[File:HistologicChapter5SkeletalMuscle.jpg|thumb|200px|Skeletal Muscle Diagram]]

On slide 20, Skeletal muscle (H&E), is one of the muscles in the larynx whose fibers appear more loosely arranged because of edema in the connective tissues; therefore, individual fibers can be seen more easily. The muscle fibers are sectioned in various planes. Keep in mind the large size (diameter) of skeletal muscle fibers as compared with smooth muscle fibers.

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Slide 8, Intervertebral disc (H&E). Some of the deep back muscle fibers attach directly to the periosteum by means of short tendons or by an apparent continuity between muscle and the connective tissue of the periosteum.

== Cardiac Muscle ==

Slide 75, Heart and Purkinje fibers (H&E), shows a portion of the left ventricle with its epicardium and endocardium, the aorta, coronary artery and vein. Purkinje fibers are present in the subendocardial areas. This slide demonstrates the major characteristics of cardiac muscle tissue: branching myocardial fibers, cross-striations, intercalated discs, and a centrally placed nucleus within each muscle fiber.

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On slide 91, Cardiac muscle (Gomori’s), the cross-striations of the myocardial fibers and the intercalated discs are more prominently displayed. The intercalated discs stain as a black line. Between the myocardial fibers the capillaries and other vessels are readily seen; the black bodies within the vessels are primarily erythrocytes. Note the strands of blue-staining connective tissue which accompany the blood vessels and which also comprise part of the endocardium and epicardium. See sketch on next page for location of Purkinje fibers.