Laboratory Exercise: Ch. 18 Cardiovascular System Part I 1 of 6 Date: Read all sections and label all figures for practice 442 EXERCISE 27 HEART STRUCTURE AND FUNCTION F. Pericardium and Layers of the Heart Wall In the mediastinum, the heart is surrounded and protected by the pericardium (peri- = around). The pericardium con- sists of an outer, tough, fibrous pericardium and an inner. delicate, serous pericardium. The fibrous pericardium attaches to the diaphragm and also to the great vessels of the heart, securing the heart in the mediastinum. Like all serous membranes, the serous pericardium is a double membrane composed of an outer parietal layer and an inner visceral layer. Between these two layers is the pericardial cavity filled with serous fluid. The serous fluid reduces friction as the heart moves. The outer parietal (paries= wall) pericardium is attached to the fibrous pericardium, and the inner visceral (viscera internal organs) pericar- dium covers the cardiac muscle. The wall of the heart has three layers: the outer epicar- dium (epi-= on, upon; cardia= heart), the middle myo- cardium (myo-muscle), and the inner endocardium (endo-= within, inward). The epicardium is the visceral layer of the pericardium. The majority of the heart is the (a) Heart in the mediastinum, anterior view diaphragm fibrous pericardium (peri-CAR-dee-um) 2 FIGURE 377 Pericardium and layers of the heart wall myocardium or cardiac muscle tissue. The endocardium is a thin layer of endothelium deep to the myocardium that lines the inside chambers of the heart and the valves. Before Going to Lab 1 Label the structures in Figures 27.7(a) and (b). LAB ACTIVITY 6 Pericardium and Layers of the Heart Wall of the pericardium using a 1-gallon 1 Simulate the formation zippered plastic bag. . Figure 27.8 shows the heart and its relationship to the pericardium. In this activity, your fist represents the heart, and the plastic bag represents the pericardium. Add a small amount of water to the bag and push out the extra air before sealing the bag. Have a lab partner place a fist (simulating the heart) at the bottom of the bag and push the fist into the bag so the bag surrounds the fist. Discuss with your lab group what the outer layer of 1 (write out the bag and the water represent. answer) (space) PERICARDIUM Heart wall endocardium fibrous pericardium myocardium parietal layer of serous pericardium Trabeculae cameae (b) Pericardium and layers of heart wall pericardial cavity visceral layer of serous pericardium (epicardium) Coronary blood vessels