Download Heart Dissection

Biology 212 – Heart Dissection
Heart Dissection
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Hold the heart in your hands. Identify anterior, posterior, superior, and lateral surfaces of
the heart. This can be difficult.
1.
Observe and describe the texture of the pericardium.
2.
Where is pericardium attached to the heart?
3.
What is the purpose of the pericardium?
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4.
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5.
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6.
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7.
If the pericardial sac is still intact, slit open the pericardium and remove it from the heart.
Observe the visceral pericardium (epicardium). Using a sharp probe, carefully prick a little
of this serous membrane away from the myocardium.
How does the visceral pericardium differ from that of the parietal pericardium?
Examine the external surface of the heart. Notice the accumulation of adipose tissue, which
in many cases marks the separation of the chambers and the location of the coronary arteries
that nourish the myocardium. Carefully scrape away some of the fat with a probe or scalpel
to expose the coronary blood vessels.
Where is the greatest accumulation of fat?
Identify the base and apex of the heart, and then identify the two wrinkled auricles, earlike
flaps of tissue projecting from the atrial chambers. The balance of the heart muscle is
ventricular tissue. To identify the left ventricle, compress the ventricular chambers on each
side of the longitudinal fissures carrying the coronary blood vessels. The side that feels
thicker and more solid is the left ventricle. The right ventricle feels much thinner and
somewhat flabby when compressed.
Why is the myocardium of the left ventricle thicker then that of the right?
Identify the vessels at the base of the heart. Identify the superior vena cava, inferior vena
cava, pulmonary trunk (dividing into pulmonary arteries), pulmonary veins, and the aorta.
Where do the superior and inferior vena cavas take blood? What other structure delivers
blood to the same area as the vena cavas? Is it oxygenated or deoxygenated blood?
Biology 212 – Heart Dissection
8.
How many pulmonary arteries do we have on our heart? Where do the pulmonary
arteries take blood? Is it oxygenated or deoxygenated blood?
9.
How many pulmonary veins do we have? Where do the pulmonary veins take blood? Is
it oxygenated or deoxygenated blood?
10.
Where is the aorta taking the blood? Is it oxygenated or deoxygenated blood? What are
the first five branches off of the aorta?
11.
Which has thicker walls, the aorta or the vena cavas? Why?
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12.
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13.
Carefully clear away some of the fat between the pulmonary trunk and the aorta to expose
the ligamentum arteriosum, a cordlike remnant of the ductus arteriosus.
What is the purpose of the ductus arteriosus in the fetus?
This particular ligament plays an important role in “deceleration” injuries (an injury
incurred when your body slows down very quickly, like in a car accident). Many people die
from these injuries. Why?
What do you suppose might happen to the ligamentum arteriosum in a deceleration
injury?
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Cut through the wall of the aorta until you see the aortic semilunar valve. Identify the two
openings to the coronary arteries which supply the heart.
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Insert a probe into the superior vena cava and use scissors to cut through its wall so that you
can view the interior of the right atrium. Do not extend your cut entirely through the right
atrium or into the ventricle. Observe the right atrioventricular valve.
14.
How many flaps/cusps does the right atrioventricular valve have?

Pour some water into the right atrium and allow it to flow into the ventricle. Slowly and
gently squeeze the right ventricle to watch the closing action of this valve. (If you squeeze
too vigorously, you’ll get a face full of water!) Drain the water from the heart before
continuing.
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Return to the pulmonary trunk and cut through its anterior wall until you can see the
pulmonary semilunar valve. Pour some water into the base of the pulmonary trunk to
observe the closing action of this valve.
Biology 212 – Heart Dissection
15.
How does the action of the atrioventricular valves differ from that of the semilunar
valves (hint…What is the purpose of these valves? What direction does blood flow
through these valves?)
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After observing the semilunar valve action, drain the heart once again. Return to the
superior vena cava, and continue the cut made in its wall through the right atrium and right
atrioventricular valve into the right ventricle. Parallel the anterior border of the
interventricular septum until you “round the corner” to the dorsal aspect of the heart.

Reflect the cut edges of the superior vena cava, right atrium, and right ventricle. Observe
the comb-like ridges of muscle throughout most of the right atrium. This is called pectinate
muscle (pectin means “comb”).
16.
This muscle is covered in a layer of endothelium that makes it extremely smooth. Why is
it important that this muscle be extremely smooth, smoother then other muscles in the
body?
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Identify, on the ventral atrial wall, the large opening of the inferior vena cava and follow it
to its external opening with a probe. Notice that the atrial walls in the vicinity of the vena
cava are smooth and lack the roughened appearance (pectinate musculature) of the other
regions of the atrial walls.
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Just below the inferior vena caval opening, identify the opening of the coronary sinus, which
returns venous blood of the coronary circulation to the right atrium. Nearby, locate the oval
depression, the fossa ovalis, in the interatrial septum. This depression marks the site of an
opening in the fetal heart, the foramen ovale, which allows blood to pass from the right to
the left atrium, thus bypassing the fetal lungs.
17.
What would be the consequence to a child if the foramen ovale failed to close?
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Identify the papillary muscle in the right ventricle, and follow their attached chordae
tendineae to the flaps of the tricuspid valve. Notice the pitted and ridged appearance
(trabeculae carneae) of the inner ventricular muscle.
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Make a longitudinal incision through the aorta and continue it into the left ventricle. Notice
how much thicker the myocardium of the left ventricle is than that of the right ventricle.
Compare the shape of the left ventricular cavity to the shape of the right ventricular cavity.
18.
Are the papillary muscle and chordae tendineae observed in the right ventricle also
present in the left ventricle?
Biology 212 – Heart Dissection
19.
How many flaps/cusps are found on the left atrioventricular valve?

Continue your incision from the left ventricle superiorly into the left atrium. Reflect the cut
edges of the atrial wall, and attempt to locate the entry points of the pulmonary veins into
the left atrium. Follow the pulmonary veins to the heart exterior with a probe. Notice how
thin-walled these vessels are.
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Properly dispose of the organic debris, and clean the dissecting tray and instruments with
warm, soapy water before leaving the laboratory.