Download Heart Dissection Guide_IGCSE

IGCSE Coordinated Sci. Y2
Mammalian Heart Dissection
Objective
Using a pig, sheep or cow heart, students will observe the major chambers, valves, and
vessels of the heart and be able to describe the circulation of blood through the heart to the
lungs and back and out to the rest of the body. (The pig, sheep, or cow heart is used because
it is very similar to the human heart in structure, size, & function.)
Materials
Dissecting pan,
dissecting kit,
safety glasses,
gloves,
mammalian heart,
lab apron
Procedure - External Structure
1. Place a heart in a dissecting pan & rinse off the excess preservative with tap water. Pat
the heart dry.
2. Locate the tip of the heart or the apex. Inside, only the left ventricle goes all the way to
the apex.
3. Place the heart in the dissecting pan so that the front or ventral side is towards you (the
major blood vessels are on the top and the apex is down). The front of the heart is
recognized by a groove that extends from the right side of the broad end of the heart
diagonally to a point above & to your left of the apex.
a) Sketch an external diagram of the heart
in your science journal. Label the apex.
b) label the approximate location
of each of the major chambers.
- right atrium
- right ventricle
- left atrium
- left ventricle
Figure 1
IGCSE Coordinated Sci. Y2
4. The heart is now in the pan in the position it would be in a body as you face the body.
Locate the following chambers of the heart from this surface:
Left atria - upper chamber to your right
Left ventricle - lower chamber to your right
Right atria - upper chamber to your left
Right ventricle - lower chamber to your left
5. While the heart is still in this position in the dissecting pan, locate these blood vessels at
the broad end of the heart:
Coronary artery – (very hard to see) this blood vessel lies in the groove on the front of the
heart & it branches over the front & the backside of the heart to supply fresh blood with
oxygen & nutrients to the heart muscle itself.
Pulmonary artery - this blood vessel branches & carries blood to the lungs to receive
oxygen & can be found curving out of the right ventricle (upper chamber to your left)
Aorta - major vessel located near the right atria & just behind the pulmonary arteries to the
lungs. Your aorta might have a curved part of this vessel known as the aortic arch.
Branching from the aortic arch is a large artery that supplies blood to the upper body.
Pulmonary veins - these vessels return oxygenated blood from the right & left lungs to the
left atrium (upper chamber on your right)
Inferior & Superior Vena Cava - these two blood vessels are located on your left of the
heart and connect to the right atrium (upper chamber on your left). Deoxygenated blood
enters the body through these vessels into the right receiving chamber.
a. Examine the dorsal (back) surface of the heart (Figure 2) Locate the stumps of two
relatively thin-walled blood vessels that enter the right atrium. The upper vessel is
the superior vena cava, and the lower one is the inferior vena cava.
b. Use your blunt probe to feel down through the superior vena cava into the right
atrium and then try to pass the probe out the inferior vena cava.
IGCSE Coordinated Sci. Y2
Procedure - Internal Anatomy: Right Side
6. Open the right atrium. To do this, follow these steps:
a. Make a long cut through the right atrium.
b. Lift the edges of the flaps and observe the wide openings where the inferior
& superior vena cava enter this chamber & notice the lack of valves.
c. Notice the thinner muscular wall of this receiving chamber.
7. Locate the valve between the right atrium and ventricle. This is called the right
atrioventricular valve, or tricuspid valve. The valve consists of three leaflets & has long
fibers of connective tissue called chordae tendinae (“tendons”) that attach it to papillary
muscles of the heart. This valve allows blood flow from the right atrium into the right
ventricle. It closes when the ventricle contracts.
8. Open the right ventricle as follows:
a. Continue cutting downward through the atrioventricular valve and the right
ventricular wall until you reach the apex of the heart.
b. Find the opening to the pulmonary artery and use the scissors to cut upward
through the wall of the right ventricle. Follow the pulmonary trunk until you have
exposed the right semi-lunar valve.
c. Examine the valve and its cusps.
9. 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.
10. Find the septum on the right side of the right ventricle. This thick muscular wall
separates the right & left pumping ventricles from each other.
11. Inside the right ventricle, locate the pulmonary artery that carries blood away from
this chamber. Find the one-way valve called the right semi-lunar valve that controls blood
flow away from the right ventricle at the entrance to this blood vessel.
IGCSE Coordinated Sci. Y2
Internal Anatomy: Left Side
12. Open the left atrium by cutting from the top of the atria down toward the ventricle
along the side ridge of the left ventricle:
a. Determine the number of blood vessel openings draining into the left atrium.
These openings belong to pulmonary veins that drain blood from the lungs. How does the
wall of the left atrium differ from that of the right atrium?
13. Start a cut on the outside of the left atrium downward into the left ventricle cutting
toward the apex until you reach the septum . Push open the heart at this cut with your
fingers & rinse out any dried blood with water. Your heart should now be completely divided
in half.
14. Inside the left chambers look for the valve that controls blood flow between the upper
left atrium and lower left ventricle. This valve is called the left atrioventricular valve, or
bicuspid valve.
15. Examine the left ventricle. Notice the thickness of the ventricular wall. This heart
chamber is responsible for pumping blood throughout the body.
16. Using your scissors, cut from the apex through the septum toward the aorta & continue
cutting to expose the valve.
17. Count the three flaps or leaflets on this valve leading from the left ventricle into the
aorta and note their half-moon shape. This is called the left semi-lunar or aortic valve.
18. Using your paper heart model, practice describing the flow of blood through the heart
with a partner in your group.
When you have finished dissecting the heart, dispose of the heart as your teacher
advises (NOT in the trash). Clean, dry, and return all dissecting equipment to the lab
cart. Wash your hands thoroughly with soap.
IGCSE Coordinated Sci. Y2
Conclusion Questions:
1. How can you tell which side of the heart is the ventral surface?
2. How many chambers are found in the mammalian heart? List these chambers.
3. Which chambers are the pumping chambers of the heart?
4. Which chambers are the receiving chambers of the heart?
5. Compare the structure of the tricuspid valve with that of the pulmonary valve.
6. How do the walls of the atria compare with the walls of the ventricles and why are they
different?
8. What is the purpose of heart valves?
8. Name & compare the heart valves found between the upper & lower chambers of the
right and left sides of the heart.
IGCSE Coordinated Sci. Y2
9. Vessels that carry blood away from the heart are called __________, while __________ carry
blood toward the heart.
10. Which artery is the largest and why?
11. What is the purpose of the coronary artery and what results if there is blockage in this
vessel?
12. Can an artery carry deoxygenated blood? Explain.
Supplementary Web Resources:
Interactive anatomy of sheep heart (Gateway Community College, AZ):
http://www.gwc.maricopa.edu/class/bio202/heart/anthrt.htm
Images of sheep heart dissection (Penn State Univ.):
http://www.bio.psu.edu/faculty/strauss/anatomy/circ/circulat.htm
Images of the human heart (University of Utah Health Sciences Center):
http://www-medlib.med.utah.edu/WebPath/CVHTML/CVIDX.html#1
This lab manual was adapted from: http://www.cohs.com/teachers/docs/155_bisc104-lab_08.pdf &
http://www.nsummit.k12.ut.us/highschool_root/html/Teacherpages/Marsh/BiologyFolders/StandardIII/ObjectiveIII/Pdf/Heart%20Dissection%20Lab.pd
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