Sheep Heart Dissection

SAFETY REMINDERS: *Scalpels are very sharp—always cut AWAY from yourself, with no fingers in the way *Putting on/taking off scalpels is just as dangerous—ask for help if you’re unsure! *When you have gloves on, don’t touch anything you can’t wash---if you touch your pencil and get formalin on it, then put that same pencil in your mouth tomorrow….

How are the parietal and visceral pericardial layers different? Gather your dissection equipment and a sheep heart. Rinse the sheep heart thoroughly with cold water to remove excess preservatives and to flush out blood clots. If the pericardial sac is intact, then remove the outer layer from its attachment points. Carefully pull the visceral pericardium (epicardium) away from the myocardium. How are the parietal and visceral pericardial layers different?

Examine the external surface of the heart Examine the external surface of the heart. Notice the accumulation of ADIPOSE tissue. This adipose usually accumulates along the boundaries of the heart chambers and along the coronary arteries. Remove as much adipose as possible. Now you should be able to identify the APEX (bottom left "point" of the heart) and the AURICLES (earlike flaps projecting from the atria). Carefully scrape away a little adipose tissue so you can see the coronary arteries.

Interventricular septum Anterior view Pulmonary trunk Right auricle Right atrium Left auricle Left atrium Right ventricle Interventricular septum Left ventricle

Superior view Superior vena cava Aorta Pulmonary trunk Pulmonary vein

Pumps blood to the entire body, through the systemic circuit 5. Squeeze each ventricle. Which is thicker? That’s the LEFT VENTRICLE—Why’s it thicker than the right? Pumps blood to the entire body, through the systemic circuit The right ventricle pumps only to the lungs through the pulmonary circuit.

Locate the PULMONARY TRUNK & AORTA on the superior aspect of the heart. The pulmonary trunk divides into the left and right pulmonary arteries. The aorta will be thicker walled and be just behind the pulmonary trunk. Clear the adipose away from these arteries.

LIGAMENTUM ARTERIOSUM (bypasses the lungs in fetus, ductus arteriosus, pulmonary trunk and aorta connection)

PULMONARY SEMILUNAR VALVE Pulmonary trunk—cut through anterior wall until you see WHICH valve? Extend the cut through pulm trunk into Rt ventricle PULMONARY SEMILUNAR VALVE

(RIGHT ATRIOVENTRICULAR VALVE) SCISSORS CUT down/around/up through AV valve—cut alongside the probe to see internal right atrium and WHICH valve? Probe into the superior vena cava through right atrium out the inferior vena cava TRICUSPID (RIGHT ATRIOVENTRICULAR VALVE)

Frontal section Pulmonary trunk via pulmonary SL valve Pulmonary veins into left atrium Right atrium Tricuspid AV valve (chordae tendinae, muscles Bicuspid AV valve w/chordae tendinae, papillary muscles Right ventricle w/thinner myocardium Aortic SL valve, out aorta Interventricular septum Left ventricle w/thicker myocardium

11. Pin back the cut edges of superior vena cava, right atrium, right ventricle

Right ventricle—papillary muscles, chordae tendineae, tricuspid valve

Dispose of solid matter in biohazard bag Wash ALL PINS, TRAYS, INSTRUMENTS, return to proper place. Gloves—dispose of in biohazard bag. WASH HANDS…

Sheep heart website http://www.gwc.maricopa.edu/class/bio202/heart/anthrt.htm