Download Lab-SheepHeartDissectionLabKD10

Sheep heart
Dissection Lab
Anatomy & Physiology
Purpose of this lab: To review the structural characteristics of the human heart and
to examine the major features of a mammalian heart.
Procedure A—External Observations of a Sheep Heart
Anterior/Ventral View
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. You may put your
finger into the blood vessels to clear them.
2. Place the heart in a dissecting tray with its anterior (ventral) surface up (See
Figure 1).
3. Most heart diagrams show the left atrium and ventricle on the right side of the
diagram. Imagine the heart in the body of a person facing you. The left side of
their heart is on their left, but since you are facing them, it is on your right.
4. Identify the right and left sides of the heart. Look closely and on one side you
will see a diagonal line of blood vessels (this may be under the layer of fat). The
half below the coronary blood vessels includes all of the apex (pointed end) of
the heart is the left side. Confirm this
by squeezing each half of the
heart. The left half will feel much
firmer and more muscular
than the right side. (The left
side of the heart is
stronger because it has
to pump blood to
the whole body. The
right side only
pumps blood to the
lungs.)
5. Locate the visceral pericardium, which appears as a thin, transparent layer
on the surface of the heart. You may use a scalpel to make a shallow
incision to examine a portion of this layer and expose the myocardium
beneath. You do NOT need to remove the pericardium.
6. 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, helping to cushion the heart.
7. Identify the following by inserting the appropriately marked pin: right atrium,
right ventricle, left atrium, left ventricle, coronary artery, apex
8. For your reference, use your scalpel to carve a small “A” or triangle shape
into the fat on the anterior side of the heart.
9. CHECK #1: Have the teacher check your pins for credit.
Posterior/Dorsal View & Blood Vessels
1. Examine the dorsal surface of the heart (Figure 2). Identify the auricles
(pouch-like extensions of the atria.)
2. Identify each of the blood vessels: aorta, vena cava, pulmonary artery,
pulmonary vein. This can be tricky, as they are cut off close to the heart and
do not appear as they do in the diagrams with which you have become
familiar. Use Figures 2 and 3 for reference. Perhaps the best way to identify
the vessels is to see where they lead. To do this, you may insert the probe or
your finger down the vessel to approximate where the vessel leads.
3. CHECK #2: When your group has identified a vessel, use one of the labeled
pins to mark it. When all vessels have been identified and pinned, have the
teacher check your pins for credit.
Procedure B: Internal Observations of
the Sheep Heart

WARNINGS:
o BE VERY CAREFUL USING THE SCALPLES. THEY ARE VERY SHARP.
o YOU WILL ONLY GET ONE CHANCE TO MAKE THE APPROPRIATE CUT.
o FAILURE TO FOLLOW THIS SET OF DIRECTIONS WILL RESULT IN THE YOUR
ENTIRE LAB GROUP’S FAILRUE OF THE LAB.
o BEFORE MAKING ANY CUT, HAVE THE WHOLE LAB GROUP AGREE.
PART 1B: DISSECTION:
1. Hold the heart with the anterior/ventral side facing the surgeon and the
superior end up. Before you make your cut, trace the path that you will cut
using the probe by carefully reading step 2 below.
2. 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.
3. 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.
4. CHECK #3: Have the teacher verify that you cut open the heart properly.
PART 2B: INTERNAL OBSERVATIONS
Heart Chambers & Valves
1. Identify and label with pins the heart chambers using the posterior half of the
heart. (Remember you carved an “A” into the anterior external surface of
the heart for reference.)
2. Also identify the following structures: tricuspid valve, bicuspid valve,
interventricular septum, chordae tendinae, and papillary muscle.
3. CHECK #4: Have the teacher verify the placement of your pins and be ready
to point out the other structures.
Blood Vessels & Path of Blood
1. Now that the heart chambers are visible, you will be able to verify whether
your identification of the blood vessels from Procedure A is correct.
2. Use the probe to insert it into each vessel and verify that it leads to the
correct locations.
a. The pulmonary vein leads to the left atria.
b. The aorta leads to the left ventricle
c. The vena cava leads to the right atria.
d. The pulmonary artery leads to the right ventricle.
3. Once you have verified the location of each valve, start at the vena cava.
Trace the path of blood through the heart chambers and vessels, ending at
the aorta. Use your notes for reference.
4. CHECK #5: Have your group (without notes) explain the path of blood flow
through the heart to the teacher.
Procedure C: Clean-up
1. Your heart and gloves will be disposed of in the trashcan near the door.
2. Your lab table must be sprayed with cleaner and wiped down.
3. Each piece of equipment must be thoroughly washed, dried, and placed on
your equipment template sheet.
4. The dissecting tray should be free of any heart materials and any fat should
be washed out using dish soap and then dried.
5. CHECK #6: Have the teacher sign your Checklist. You will be dismissed as a
group. No one may leave until the Checklist is signed. Leaving prior to this
will result in a zero on the lab.