Anatomy & Physiology II

Spring 2007

Lab 2: Sheep Heart Dissection Procedure

Instructions:

For diagrams of the human heart see textbook pp. 719- 725

  1. Remove the outer parietal pericardium (if present) by cutting from the apex of the heart to the base and gently peeling the parietal pericardium over the heart mass towards the base (top and widest part) of the heart. You will need to use your scalpel to separate the parietal pericardium from the blood vessels at the base of the heart.
  2. Identify the front of the heart, easily seen by the interventricular sulcus between the ventricles. The pulmonary trunk runs across the base of the heart in the front.
  3. Identify the location of the left and right ventricles by squeezing the apical walls of the heart. You will be able to feel the hollow ventricular chambers as you squeeze. The aorta comes from the left ventricle (the biggest chamber), and is often easy to identify.
  4. Locate the following blood vessels at the base of the heart:

aorta

pulmonary trunk (some hearts may have the right and left pulmonary arteries)

pulmonary veins

vena cava

 

First Cut: Dissection of right atrium and right ventricle

4. Cut through the vena cava into the right atrium to expose the right AV valve (tricuspid valve). Note the opening of the coronary sinus in between the inferior vena cava and the right AV valve. Fill the right ventricle with water, pouring it in through the right AV valve. Gently squeeze the walls of the ventricle to note the closing action of the valve’s cusps.

5. Drain the water from the right ventricle and continue the cut with scissors from the right atrium through the right AV valve down to the apex of the heart. Expose the right ventricle and locate the papillary muscles and chordae tendineae in the right ventricle. Cut upwards along the interventricular and interatrial septa towards the base of the heart to expose the pulmonary semilunar valve.

 

Second Cut: Dissection of left atrium and left ventricle

6. Insert one blade of your scissors into the left atrium. Cut through the left atrium into the left ventricle to the apex of the heart. Also cut upwards from the left ventricle into the aortic arch to expose the aortic semilunar valve and the two openings to the coronary arteries.