HEART DISSECTION LAB

Procedure Obtain a dissection pan and dissecting kit.

Procedure Obtain a heart and rinse off the excess preservative with tap water. Pat the heart dry.

Place the heart in a dissection pan.

Observe the pericardium Observe the pericardium. 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

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.

RECORDERS- type your group response in your google doc. Question 1: What is the purpose of adipose tissue surrounding the heart? Question 2: What is the function of the pericardium?

Now you should be able to identify the apex (bottom left "point" of the heart) and the auricles (earlike flaps projecting from the atria).

Locate the pulmonary trunk and the aorta on the superior aspect of the heart. Clear the adipose away from these arteries. The pulmonary trunk divides into the left and right pulmonary arteries. The aorta will have a large branch coming from beneath the pulmonary trunk.

Recorders- Type your response Question 3: What are the functions of the coronary vessels seen on the surface of your heart? Take a picture and upload into your google doc. Label coronary vessels, apex, base.

Starting at the apex and moving towards the base, …….

Make a coronal (frontal) cut through the heart Make a coronal (frontal) cut through the heart. Stop cutting when your knife reaches the top portions of the atria.

Notice that the heart is made up of three histological layers: the epicardium, the myocardium and the endocardium

Locate the side with the thickest myocardial wall Locate the side with the thickest myocardial wall. This will orient you to the left side of the heart

You should see that there are spaces (or "chambers") on the left and right sides of the lower heart. These are the left and right ventricles

Question 4: Which side of the heart is thickest? Question 5: Why is this side of the heart thickest?

You should also see a thick structure dividing the two ventricles, the bulk of which is comprised of cardiac muscle. This is the interventricular septum.

Question 6: Why does the human heart need to be divided into two sides by the septum?

The ventricles are divided from the chambers directly above them by atrioventricular (or "AV") valves. These valves have flaps (or "cusps") to which "heart strings" attach.

The left AV valve has two cusps, so it can be referred to as being a "bicuspid" valve. The right valve has three cusps, so it can be referred to as being a "tricuspid" valve.

The strings that attach to the AV cusps are called chordae tendinea.

The chordae tendineae are anchored to the ventricular walls via papillary muscles.

Question 7: Why does the AV have strings attached to them?

Remove the right ventricular wall and cut into the pulmonary trunk in order to view the pulmonary semilunar valve.

Remove the left ventricular wall and cut into the aortic trunk in order to view the aortic semilunar valve.

Question 8: When the atria contract, what happens to the AV valves? Question 9: When the ventricles contract what happens to the AV valves? Question 10: When the ventricles contract what happens to the semi lunar valves?

POSTERIOR VIEW Find the great vessels on the base of the heart POSTERIOR VIEW Find the great vessels on the base of the heart. Insert a probe to identify vessels.

POSTERIOR VIEW Locate the position of the probe in the heart POSTERIOR VIEW Locate the position of the probe in the heart. Identify the aorta, vena cava and pulmonary artery.

FINAL QUESTION! Take a picture a showing the probe- in one of your vessels. Label the vessel. Label right atria, left atria, right ventricle, left ventricle, septum, av valve, chordae tendonae, aorta, vena cava, pulmonary vessel

Discard all heart materials in the trash. Clean all tools in the sink with soap. Clean your pan. Spray and wipe your desk.