Download click - Uplift North Hills Prep

Sheep Heart Dissection
Overview
You will work in small groups to dissect a preserved sheep heart. Your group will present your dissection to your teacher
by identifying major blood vessel, valve, and chamber of the heart and explaining the structural differences between the
left and right side of the heart. You should also describe the path blood takes as it moves through the heart. Everyone
in the group should participate in the presentation, and you should use your notes as little as possible during the
presentation.
Pre-lab
To prepare for the lab, label the diagram of the heart and add arrows that demonstrate how blood flows through the
heart.
Dissection instructions
1. Obtain a sheep heart, a dissecting tray, a scalpel, dissection scissors, a probe, and a few pencils.
2. Carefully examine the heart to determine which sides are the anterior and posterior sides, and which
are sides are the left and right. The anterior side is smooth, and round, and has a large blood vessel
moving from the upper right side of the heart to lower left. The apex points towards the left side of
the heart. The left side will also feel much firmer if you squeeze it than the right side, due to the
greater musculature of the left ventricle. (Refer to the diagrams below)
3. Identify the major blood vessels that leave the heart. Stick a probe or your finger through each vessel
to determine from which chamber it leaves or enters. You may want to place marked pencils in each
vessel to indicate which is which.
a. Superior vena cava – Turn the heart so that its posterior side is facing you. Find the large
opening at the top of the heart next to the right auricle (the auricles are dark flaps of tissues
that are extensions of the atria). This is the superior vena cava. Stick a probe through the
superior vena cava; you should be able to feel the probe inside the right atrium.
b. Inferior vena cava – You will find the inferior vena cava just inferior and to the left of the
superior vena cava. Stick a probe through the inferior vena cava; you should be able to feel the
probe inside the right atrium.
c. Pulmonary vein – The pulmonary vein is next to the left auricle. Stick a probe through the
pulmonary vein; you should be able to feel the probe inside the left atrium.
d. Aorta – The large vessel on the top of the heart towards the anterior side is the aorta. Stick a
probe through the aorta; you should be able to feel the probe inside left atrium.
e. Pulmonary arteries – You will find the pulmonary arteries anterior and towards the left of the
atria. Depending on where the artery was cut, you may see this as one big opening (the
pulmonary trunk) or as two openings (left and right pulmonary artery). Stick a probe through
the pulmonary artery; you should be able to feel it within the right ventricle.
Stop and present the major
blood vessels and the flow of
blood through the heart to your
teacher before starting the
dissection!
Heart dissection
4. Put your scissors into the pulmonary artery and cut down into the right ventricle, cutting parallel to
the coronary artery. Stop cutting when you reach the end of the ventricle.
Peel back the wall of the heart along your cut to observe
the two valves of the right ventricle.
The valve between the pulmonary artery and the right
ventricle is the pulmonary semilunar valve. Notice how
the structure of the pulmonary semilunar valves
prevents blood from flowing back into ventricle.
The valve between the right atrium and the right
ventricle is the right atrioventricular valve, also called
the tricuspid valve. Notice the chordae tendinae (aka
heart strings) which anchor the valve the papillary
muscles of the ventricle. This valve prevents the blood
from moving back into the atrium.
5. Put your scissors into the superior vena cava and cut down into the right atrium. Stop when you reach
the right atrioventricular valve.
With this cut, we can see into the right
atrium and we can see the right
atrioventricular valve from the other
side.
Notice how thin the walls of the atrium
are compared to the ventricle.
6. Put your scissors into the aorta and cut down until you reach the aortic semilunar valve. Notice that
the aortic semilunar valve prevents blood from flowing back into the left ventricle.
7. Continue cutting into the wall of the left ventricle. Stop when you reach the end of the ventricle.
Peel back the wall of the left ventricle to observe the left atrioventricular valve, also called the mitral
valve. Notice the chordae tendinae (aka heart strings) which anchor the valve the papillary muscles of the
ventricle. This valve prevents the blood from moving back into the atrium.
Compare the thickness the wall of the left ventricle with that of the right ventricle. What is the explanation for
this difference?
8. Place your probe through the left atrioventricular valve into the left atrium.
Stop and present the valves and chambers to your teacher. Also be sure to discuss the differences
between the right and left sides of the heart.
Rubric
Pre-Lab Questions
Achievement Descriptor
Level
0
The pre-lab questions were not completed before the lab began or little attempt has been
made to accurately answer the questions.
1
The answers to the pre-lab questions partially accurate.
2
The answers to the pre-lab questions were mostly accurate.
3
The answers to the pre-lab questions were completely accurate.
Group Work & Lab Skills
Achievement Descriptor
Level
0
Group members did not follow safe lab procedures.
1
Group members had difficulty working together. Scholars used equipment carefully and
followed proper clean up and disposal procedures.
2
Group members mostly worked together effectively during the dissection and presentation.
Scholars used equipment carefully and followed proper clean up and disposal procedures.
3
All group members worked together safely and effectively during the dissection and
presentation. Scholars used equipment carefully and followed proper clean up and disposal
procedures.
Presentation
Scholars should identify the following structures: superior vena cava, inferior vena cava, pulmonary arteries,
pulmonary veins, aorta, right atrium, left atrium, right ventricle, left ventricle, aortic semilunar valve,
pulmonary semilunar valve, right atrioventricular valve, left atrioventricular valve.
Scholars should describe the flow of blood through the heart.
Scholars should describe and explain the structural differences of the left and the right side of the heart.
Achievement Descriptor
Level
0
Scholars showed little address the points of the presentation.
1
Scholars correctly addressed some points of the presentation (listed above) while using
notes and/or some prompting from the teacher or other group members.
2-3
Scholars correctly addressed most points of the presentation (listed above) with some use of
notes and/or some prompting from the teacher or other group members.
4-5
Scholars correctly addressed all points of the presentation (listed above) with minimal use of
notes .
Achievement
Level
11
10
9
8
Grade
100
95
85
80
Achievement
Level
7
6
5
4
Grade
75
70
65
60