SHEEP HEART DISSECTION
Introduction
Sheep have a four-chambered heart, just like humans. By studying the anatomy of a sheep's heart,
you can learn about how your own heart pumps blood through your body and keeps you alive!
Pre-Lab Questions
1) On the heart diagram, label the following structures:
a. Superior and Inferior Vena Cava
b. Right and Left Atria
c. Right and Left Ventricles
d. Right and Left Pulmonary
Arteries
e. Right and Left Pulmonary Veins
f.
g.
h.
i.
j.
Aorta
Tricuspid Valve
Mitral Valve
Pulmonary Valve
Aortic Valve
2) On the heart diagram, indicate which blood vessels send blood to the lungs and body, and
which blood vessels bring blood back to the heart from the lungs and body.
3) On the heart diagram, color the side of the heart that pumps oxygen poor blood blue and the
side that pumps oxygen rich blood red.
Checkpoint
1
DO NOT MOVE ON UNTIL INSTRUCTOR HAS CHECKED YOUR WORK!
Dissection Preparation
Complete the Dissection Set-up Checklist. Instructor will check your set-up and give you your preserved
sheep heart for the dissection.
Procedure
Orienting the Heart
1. Locate the right and left sides of the heart
a. Locate the ventral side of the heart. Find the diagonal
line on the front of the heart. This diagonal line is the
Coronary Artery.
b. Locate the Superior and Inferior sides of the heart. The
superior side will have several blood vessels coming
off of it. The inferior side will have the Apex.
c. Position the heart on your dissecting tray so that the
Coronary Artery is face up, and the Apex of the heart is
pointing generally toward the bottom of the dissecting
tray. Make sure that the Right Ventricle is on YOUR
LEFT and the Left Ventricle is on YOUR RIGHT. The
Left Ventricle will feel much firmer than the right
ventricle because it is more muscular than the right
ventricle.
Q1) Using your knowledge of the heart, think about where
the blood is going from each ventricle and hypothesize why the Left Ventricle is so much
more muscular than the Right Ventricle.
Checkpoint
DO NOT MOVE ON UNTIL INSTRUCTOR HAS CHECKED YOUR WORK!
External Anatomy
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USE ONLY PUSH PINS AND PROBES FOR THIS PART OF THE LAB! DO NOT CUT ANYTHING!
1. Locate and label with a push pin the following external structures. You may use the diagrams in the
dissection guide to help you locate the structures.
a. Auricles (flaps on the superior surface of the heart)
b. Superior Vena Cava (will be near the right auricle)
c. Inferior Vena Cava (below the Superior Vena Cava)
d. Pulmonary Vein (near the left auricle)
e. Aorta (on the top of the heart, with multiple arterial branches coming off of it)
Q2) Carefully put a probe about 1 inch into the Superior and Inferior Vena Cava. What chamber of
the heart will your probes enter?
Q3) Carefully put a probe about 1 inch into the Pulmonary Vein. What chamber of the heart will
your probe enter?
Checkpoint
DO NOT MOVE ON UNTIL INSTRUCTOR HAS CHECKED YOUR WORK!
3
Internal Anatomy
1. Using a scalpel or scissors, cut through the right atrium and right ventricle. Start at the Superior
Vena Cava and work downward to the bottom of the right ventricle.
2. Put a probe through the Pulmonary Artery so that you can see it enter the right ventricle. Leave it
there.
3. Label with push pins the following structures:
Checkpoint
a. Tricuspid Valve
b. Right Atrium
c. Right Ventricle
d. Pulmonary Valve
4
DO NOT MOVE ON UNTIL INSTRUCTOR HAS CHECKED YOUR WORK!
4. Now, cut through the left atrium and left ventricle.
5. Put a probe through the aortic valve and out one of the holes in the aorta. Leave it there.
6. Label with push pins the following structures:
a. Mitral Valve
b. Left Atrium
c. Left Ventricle
d. Aortic Valve
Q4) Examine the Tricuspid Valve and Mitral Valve. Move them around. Explain how the cordae
tendonae work and why they must be very strong.
Checkpoint
DO NOT MOVE ON UNTIL INSTRUCTOR HAS CHECKED YOUR WORK!
5
Dissection Clean-Up
Complete the Dissection Clean-up Checklist. Instructor will check your clean-up and collect your lab. If
you finish early, work on homework.
Checkpoint
DO NOT MOVE ON UNTIL INSTRUCTOR HAS CHECKED YOUR WORK!
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