Name ____________________________
Date _________________
Mammalian Heart Dissection – Part 2
Note: You are not required to hand in answers to the questions posed in this dissection guide,
but you will want to know the answers!
Materials
•
sheep heart
•
dissecting tray
•
dissection kit
•
gloves
Procedure
Part 2 – Internal Anatomy
1. Review the outer part of the heart and make sure you know where these structures
are: left and right ventricle, left and right atrium, pulmonary artery, pulmonary veins,
aorta, coronary artery, apex, superior and inferior vena cava.
2. Using your scissors, make a longitudinal cut along the lateral surface of the heart
from the top of the right atrium to the bottom of the right ventricle.
3. By prying open this side of the heart you should be able to see inside the right
atrium and right ventricle. Locate the tricuspid valve between the right atrium and
ventricle. The valve consists of leaflets (or flaps) and has long fibers of connective
tissue called chordae tendinae
Question: How many flaps does the tricuspid valve have?
4. Use your fingers to feel the thickness of the right ventricle and its smooth lining. Also
note the network of irregular muscular cords on the inner wall of this chamber.
5. Locate the vessels attached to the right side of the heart. In the atria, locate the
entry point for the vena cava. In the ventricle, locate the pulmonary artery that
carries blood away from this chamber. Find the one-way valve called the
pulmonary valve that controls blood flow away from the right ventricle at the
entrance to this blood vessel.
Question: Does the vena cava have a valve at the opening to the right atrium?
6. Using your scissors, make a longitudinal cut along the lateral surface of the heart
from the top of the left atrium to apex of the heart.
7. By prying open this side of the heart you should be able to see inside the left atrium
and left ventricle. Locate the bicuspid valve between the left atrium and ventricle.
Notice the chordae tendinae attaching to mounds of cardiac muscle protruding
from the inner surface of the ventricle. These are the papillary muscles. Papillary
muscles contract very early in the cardiac cycle and keep the valve flaps taut so
they cannot fall back into the atria.
Question: How many flaps does the bicuspid valve have?
What would happen if the chordae tendineae were ruptured?
8. Examine the left atrium. Find the openings of the pulmonary veins form the lungs.
Observe the one-way, semi-lunar valves at the entrance to these veins.
9. Find the septum, the thick muscular wall that separates the right and left chambers
of the heart. You will need to now cut along the septum to completely remove the
ventral surface of the heart.
10. Examine the thickness of the walls of different chambers of the heart
Question: Compare and contrast the thickness of the atrial and ventricular walls. As well
compare and contrast the right and left ventricular walls. Why are they different?
Observations
1. Prepare a formal drawing of the internal anatomy of your heart in this position.
a. Title: Internal Mammalian Heart (Sheep)
b. Lower Right subtitle: Ventral View, longitudinal cross section
c. You will need to determine the scale factor of your drawing (1x, 1.5x 2x?)
d. Labels all structures you identified in the lab!