Download Sheep Heart Dissection Lab

Sheep Heart Dissection Lab
Purpose of this lab: To examine the major features of a mammalian heart.
YOU WILL CREATE A DIGITAL SLIDE SHOW OF YOUR PICTURES THAT YOU WILL
SHARE WITH ME OR EMAIL AS AN ATTACHMENT AT THE END OF THIS LAB.
Dissection of a Sheep Heart.
1. Obtain a preserved sheet heart. Rinse it in water thoroughly to remove as much of the
preservative as possible. Also run water into the larger blood vessels to force any blood
clots out of the heart chambers.
2. Place the heart in a dissecting tray with its anterior surface up (See Figure 36.4 below).
Proceed as follows:
a. Locate the visceral pericardium, which appears as a thin, transparent layer
on the surface of the heart. Use a scalpel to remove a portion of this layer
and expose the myocardium beneath. Also note the abundance of fat along
the paths of various blood vessels. This adipose tissue occurs in the loose
connective tissue that underlies the visceral pericardium.
b. Identify the following:
right atrium, right ventricle, left atrium, left ventricle, coronary
arteries
PHOTO 1: TAKE A PHOTO AND LABEL: VISCERAL PERICARDIUM, ADIPOSE
TISSUE, MYOCARDIUM, RIGHT ATRIUM, LEFT ATRIUM, RIGHT VENTRICLE, & LEFT
VENTRICLE
3. Examine the posterior surface of the heart. Locate the stumps of two relatively thinwalled blood vessels that enter the right atrium. Demonstrate this connection by passing a
slender probe through them. The upper vessel is the superior vena cava, and the lower
one is the inferior vena cava.
4. Open the right atrium. To do this, follow these steps:
a. Insert a blade of the scissors into the superior vena cava and cut downward
through the atrial wall. DO NOT CUT INTO THE RIGHT VENTRICLE.
b. Open the chamber, locate the tricuspid valve and examine its cusps.
PHOTO 2: TAKE A PHOTO AND LABEL: RIGHT ATRIUM & TRICUSPID VALVE
5. Open the right ventricle as follows:
a. Continue cutting downward through the tricuspid valve and the right
ventricular wall until you reach the bottom of the heart.
b. Find the opening to the pulmonary trunk and use the scissors to cut upward
through the wall of the right ventricle. Follow the pulmonary trunk until you
have exposed the pulmonary valve.
c. Examine the valve and its cusps.
PHOTO 3: TAKE A PHOTO AND LABEL: RIGHT VENTRICLE & PULMONARY VALVE
6. Open the left side of the heart. To do this, follow these steps:
a. Insert the blade of the scissors through the wall of the left atrium and cut
downward to the bottom of the heart.
b. Open the left atrium and locate the openings of the pulmonary veins.
c. Examine the bicuspid valve (mitral valve) and its cusps.
d. Also examine the left ventricle and compare the thickness of its wall with
that of the right ventricle.
PHOTO 4: TAKE A PHOTO AND LABEL: LEFT ATRIUM, LEFT VENTRICLE, &
BICUSPID (MITRAL) VALVE
8. Use the scalpel to cut starting in the left atrium through the coronal plane (dividing
anterior and posterior portions equally), downward through the left ventricle to the apex of
the heart. (Note that the myocardium wall is very thick here.) The cut will continue back up
from the apex, through the right ventricle, and through the right atrium. YOU WILL NOT
CUT THROUGH THE BLOOD VESSELS.
9.
To fully open the heart, orient the heart with the apex upward and carefully continue
to cut through the myocardium from the apex toward the atria. Again, DO NOT CUT
THROUGH THE BLOOD VESSELS. The vessels will hold together the anterior and
posterior portions of the heart.
10.
Position the heart with the anterior side facing you. With the heart fully opened (still
attached at the blood vessels). Take a photo.
PHOTO 5: TAKE A PHOTO AND LABEL: INTERVENTRICULAR SEPTUM, RIGHT
ATRIUM, LEFT ATRIUM, RIGHT VENTRICLE, & LEFT VENTRICLE
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Analysis Questions
1. How many chambers are found in the mammalian heart? List these chambers.
2. Which chambers are the pumping chambers of the heart?
3. Which chambers are the receiving chambers of the heart?
4. How do the walls of the atria compare with the walls of the ventricles and why are they
different?
5. What is the purpose of heart valves?
6. Vessels that carry blood away from the heart are called __________, while __________
carry blood toward the heart.
7. What is the purpose of the coronary artery and what results if there is blockage in this
vessel?