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Investigation: Heart Structure and Function
Problem: How is the structure of the heart related to its function?
Background Information: The heart is essentially a muscular pump that
keeps blood moving in a continuous, one way flow around the body. Like
human-made pumps, it contains valves and can alter the volume of fluid
holding cavities within it. In this activity, you will study and compare the
different areas of the heart and investigate the relationship between
structure and the function of each part.
Experimental Design: You will investigate the anatomy of the heart by
dissecting a real heart. As you explore and sketch different parts of this
vital organ, consider how their characteristics help the heart to function.
Questions throughout the procedure will direct your attention to significant
features.
Materials: gloves, dissecting tray, fresh animal heart, scalpel, paper
towels.
CAUTION: USE CARE WITH SHARP CUTTING TOOLS AND
NEEDLES!
Procedure: Part A: Opening the Heart
1. Obtain a dissecting tray and scalpel. If you are doing the cutting,
obtain a pair of rubber gloves and a fresh heart. When you are
finished with the animal tissue, dispose of it as instructed by your
teacher. Wash the lab bench and your
hands well at the end of the lab.
Wash the dissecting tray and put a
paper towel on top.
2. Locate the right atrium with
your thumb by squeezing the heart
and feeling for the thin walled
chamber. Before you cut, ask me!
3. Trace a shallow incision, not
more than 5mm deep, from the atrium
down to the right ventricle and up to
the apex of the heart. Watch your teacher as they demonstrate
this!
4. Continue the shallow cut around the apex and up the left ventricle
so that you have a line dividing the ventricles into 2 equal halves.
Cut along the shallow line to divide the ventricles in half. DO NOT
cut the heart completely in half!
Part B: Exploring the Ventricles
5. Are the walls the same thickness in both ventricles?
_______________________________
Where (what organ) is blood pumped to from the right ventricle?
_____________________________
Compare and Contrast the appearance of each ventricle as
related to it’s function! (Hint: Why is it thicker?)
6. In the living body, one ventricle contains oxygenated blood (with
high oxygen content) and the other contains deoxygenated blood
(with low oxygen content). Based on the direction of flow to and
from the heart:
Which ventricle contains oxygenated blood? ___________
Which ventricle contains deoxygenated blood? _________
Part C: Exploring the Atria
7. Externally, the atria resemble small, ear-like flaps on the top of the
heart. Label the locations of the left and right ventricles and the
left and right atria on the diagram.
8. On the diagram, add arrows to
show the direction of blood flow
between the body and atria and the
body and the ventricles. What prevents
blood from flowing in the opposite
direction between the atria and
ventricles?
pressure of the blood pushes the flaps of the AV valve together,
closing the passage between the ventricle and the atrium. The
blood, under high pressure, is forced out of the left ventricle into a
large artery called the aorta. What might happen, over time, if the
left AV valve fails to close properly?
12. After the blood passed into the aorta, the left ventricle relaxes.
What happens to the left valve when this occurs? _____________
What happens to the blood in the left atrium when this occurs?
____________________
Part D: Exploring the Left Side of the Heart
9. Make an incision in the wall of the left atrium. Gently push the
handle of the probe into this incision and feel the atrioventricular
valve, which divides the left atrium and the left ventricle. Does the
left atrium in the living body contain oxygenated blood or
deoxygenated blood? _________________
10. The AV valve has 2 thin, sail like transparent structures that are
held by strong, white, cord-like structures. Carefully push the
handle of your probe through the valve into the left ventricle. What
is the structure and operation of this valve?
13. The left atrium is refilled with blood from the pulmonary veins. 2
Pulmonary veins enter it from the left lung and 2 from the right.
The thin walls of these veins may make them difficult to find. Use
the handle of the probe inside the left atrium to find the pulmonary
veins.
Why do they have thin walls compared to the aorta?
_________________________________
14. Find where the aorta leaves the left ventricle and carefully push
the handle of your probe into it. Note the location where the probe
exits the heart. Remove the probe and gently push the handle in
the reverse direction, from the exit of the aorta to the left ventricle.
At a point close to the left ventricle, the probe may be stopped by
a valve called the aortic semilunar valve. Leave the probe in place
and make an incision to find the valve.
What is the function of this valve? ________________________
11.
Imagine the blood followed
the path of your probe from
the left atrium into the left
ventricle. Now full of blood, the left ventricle contracts! The
Part E: Exploring the Right side of the heart
15. The heart is actually 2 pumps. The left side receives the blood
from the lungs and pumps it to the rest of the body. The right side
receives blood from the body and pumps it to the lungs. Locate
the AV valve, which separates the right atrium from the right
ventricle.
Does the right atrium in the living body contain oxygenated blood
or deoxygenated blood? ______________
16. The right AV valve is similar to the left AV valve except that it has
3 sail like flaps instead of 2. Explore the working of this valve with
your probe.
What happens to the valve when the right ventricle contracts?
_______________________
Where does the blood go when the right ventricle contracts?
________________________
17. After the blood has passed out of the right ventricle, the ventricle
relaxes.
What happens to the AV valve when this occurs?
________________
What happens to the blood in the right atrium when this occurs?
18. The right atrium is refilled with blood from the body through 2 large
veins, called the superior and inferior vena cave. Use the Handle
of your probe inside the right atrium to find these thin walled veins.
The superior vena cava enters near the top of the right atrium and
the inferior vena cava enters from the bottom of the right atrium.
19. Find where the blood leaves the right ventricle through the
pulmonary artery. How does the appearance of this artery
(thickness, etc.) compare with that of the aorta?
____________________________________________________
___________________
Suggest a reason for any differences you notice.
20. Carefully push the probe into the pulmonary artery and notice the
location where the probe exits the heart. Remove the probe,
gently push the handle in the reverse direction (towards the right
ventricle). The probe may be stopped by the pulmonary semilunar
valve. Leave the probe in place and make an incision to find the
valve.
What is the function of this valve?
____________________________________________________
Analysis:
21. Complete the following table, choosing open or closed for the
valves and yes or no for blood movement:
22. Complete the following table and place check marks in the correct
place in each column:
Chamber or
Vessel
Right Atrium
Left Atrium
Right ventricle
Left ventricle
Aorta
Pulmonary Artery
Pulmonary vein
Vena Cava
Ventricles contract
Valve/ Blood
Movement
Semilunar valves
AV valves
Blood moves into
arteries
Blood moves into
atria
Blood moves into
ventricles
Ventricles Contracted
Ventricles relax
Ventricles relaxed
Contains Oxygenated
Blood
Contains Deoxygenated
Blood
Extension:
23. The living heart makes a 2 beat sound described as “lub-dubb”.
Both beats are produced by a pair of valves closing in the heart.
The “ lub” sound is loud, where as the “dub” sound is softer.
Which valves close on the “lub” beat?
_______________________
Which valves close on the “dub” beat?
______________________