Download Pig Heart Dissection Lab Safety Follow safe laboratory practices

Pig Heart Dissection Lab
Safety
Follow safe laboratory practices when performing any dissection. Wear safety glasses or goggles,
gloves, and lab aprons when dissecting. Perform dissections on a dissecting tray or pan to contain
specimens and fluids. Be careful when using sharp instruments, such as scalpels & blades, forceps,
dissecting needles, and scissors.
Assignment
As you go through this dissection, you will be expected to make sketches and observation notes in
your lab notebook. There is an external heart anatomy diagram (Figure 1) included that you should
attach to your lab notebook and you will be expected to identify the parts. You should also make
additional detailed sketches of the internal anatomy of the heart, labelling each identifiable part
clearly. So as not to contaminate your notebook or pencil, you may take photos of the heart you are
dissecting to refer to later on. You will also be expected to answer the analysis questions in your lab
notebook in complete sentences.
Procedure
1. Review the definitions you sheet you completed before the dissection, as well as any homework
or class notes to guide you. Refer to the diagram of the heart as a general reference as you
observe and identify external and internal structures.
2. Identify the base and apex of the heart. At the base are two ear-like auricles. These are the two
atria. The rest of the heart is composed of the two ventricles. To identify the right ventricle
from the left, gently squeeze the chambers on each side of the heart. The right ventricle has
thinner walls and will compress more easily. The left ventricle has thick muscular walls due to its
function of pumping blood to the systemic circuit.
3. 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.
4. Run some water through the tricuspid valve to fill the chamber of the right ventricle. Gently
squeeze the ventricles and watch the cusps of the valve as the water moves up against them.
5. Use a probe to push through the opening of the valve into the right ventricle. Observe the
number of flaps, or cusps, that make up this valve.
6. Refer to the dissected mammal heart image to the right. Make an incision through the right
ventricle and remove the front portion of the wall.
7. Locate the aorta. This vessel has a larger diameter than the pulmonary trunk and will branch
immediately after leaving the left ventricle. Cut through the wall of the aorta until you see the
aortic semilunar valve, which prevents blood from entering the left ventricle.
8. Locate the pulmonary trunk, which is located anterior to the aorta. Cut through the wall of this
vessel until you see the pulmonic semilunar valve, which prevents blood from entering the right
ventricle.
9. Observe the difference in the diameter of these two blood vessels.
10. Cut through the wall of the left atrium to view the bicuspid valve. Observe the number of cusps
that make up this valve.
Figure 1 – External heart anatomy
Analysis Questions
1. Describe (in order) the path of blood through the major blood vessels, chambers, and valves
from vena cava to aorta.
2. Describe the structure of the tricuspid valve and compare it to the structure of the pulmonary
valve. What similarities and differences exist, and why might this be?
3. Describe the action of the tricuspid valve when you squeezed the water-filled right ventricle.
4. Describe the function of the chordae tendinae and the papillary muscles, and explain how their
structure relates to their function.
5. What is the significance of the difference between the difference in thickness between the atria
and the ventricles?
6. What is the significance of the difference in thickness between the walls of the aorta and the
walls of the pulmonary trunk?
7. What is the significance of the difference in thickness of the ventricular walls (right versus left)?