Caption: Contracted heart muscle fibers (ventricle) with partial overlying pericardium and collagen fibers. The heart muscle produces regular electrical impulses causing the muscle myofibrils (actin and myosin) to slide over one another and contract the cardiac muscle. The pericardium is a double-walled, membranous sac surrounding the heart. The pericardium has a tough outer fibrous layer (fibrous pericardium) and a delicate serous layer (serous pericardium). The inner serous pericardial layer is the wall adjacent to the heart (partially seen here). It is split into two layers, the epicardium (just above the heart) and the parietal layer. Between the two layers is the pericardial cavity, which contains serous fluid. Both layers consist of flattened squamous epithelial cells and connective tissue. The serous pericardium lubricates the heart, preventing friction. Pericarditis is an inflammation of the pericardium.
Magnification*: x440
Type: SEM
Copyright 2009 Dennis Kunkel Microscopy, Inc.
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