This document provides instructions for dissecting a sheep heart to observe its internal structures. The instructions include identifying the base and apex, locating the atria and ventricles, making cuts to view the valves between the chambers, and tracing the blood flow pathways from the ventricles to the arteries. The left ventricle is noted to have thicker walls than the right ventricle.

4.  Identify the base and apex of the heart
 Locate the auricles and identify the two atria

5.  Identify the two ventricles
 The right ventricle will have thinner walls
 The left ventricle will have thicker, more
muscular walls

6.  Cut through the wall
of the right atrium
and remove a
portion of the wall
 Be careful not to cut
the right ventricle
 Observe the tricuspid
valve

7.  Use a probe to push
through the tricuspid
valve into the right
ventricle
 Observe the number
of flaps

8.  Make an incision through the right ventricle
and remove the front portion of the wall

9.  Locate the aorta
 Cut through the wall of the aorta until you
see the aortic semilunar valve

10.  Locate the pulmonary trunk
 Cut through the vessel wall until you see the
pulmonic semilunar valve

11.  Note the
difference in the
diameters of the
aorta and
pulmonary trunk

12.  Cut through the wall
of the left atrium to
view the bicuspid
valve
 Observe the number
of flaps

13.  Make an incision through the left ventricle
inferior to the interventricular groove
 Remove the lower front portion of the wall

14.  Notice the difference in the size of the two
ventricles

15.  Observe the interventricular septum that
divides the two ventricles

16.  Observe the
bicuspid valve
and the
supporting
chordae
tendineae and
papillary
muscles

18.  Using a probe, trace the pathway of blood
from the left ventricle through the semilunar
valve to the aorta

19.  Repeat this action for the right ventricle,
tracing the pathway from the ventricle
through the pulmonic semilunar valve to the
pulmonary trunk