BIOL&242
Lab 30
For this lab you will: look at cardiac muscle tissue and do a sheep heart dissection.
Activity 4- Please sketch and clearly label cardiac muscle tissue. Be sure to label: nuclei, striations,
intercalated discs (but don’t spend more than 5 minutes looking for one!), and any obvious branching
points.
A. Name the two different types of membrane proteins that are found at an
intercalated disc. State the FUNCTION of each.
B. State three differences between cardiac muscle and skeletal muscle.
Dissect a calf heart. You do not need to turn in any sketches from the heart dissection. Use the
instructions from pages 449-452 to guide your dissection. Note that there may be small differences
(sheep versus calf). ALSO, you should work on page 456 of our lab manual during the dissection.
Here is a list of external and internal anatomical features to look for.
External anatomy- identify the right atrium, auricle of right auricle, right ventricle, left atrium, auricle
of left atrium, left ventricle, pulmonary trunk, aorta, coronary sulcus (note fat), anterior interventricular
sulcus, posterior interventricular sulcus.
When you have completed this, you should next perform a cut into the wall of the heart. PLEASE
CHECK WITH ME BEFORE CUTTING! I NEED TO CHECK THAT YOU KNOW ANTERIOR
FROM POSTERIOR!
One option is to insert your dissecting scissors into the superior vena cava and make an incision down
through the wall of the right atrium and ventricle. Pull the two sides apart and look for three flaps of
membrane. These membranes form the tricuspid valve between the right atrium and the right
ventricle. The membranes are connected to flaps of muscle called the papillary muscles by tendons
called the chordae tendinae or "heartstrings."
Next, insert your probe into the pulmonary artery and see it come through to the right ventricle. Make
an incision down through this artery and look inside it for three small membranous pockets. These
form the pulmonary semilunar valve which prevents blood from flowing back into the right ventricle.
From this point, you can repeat similar cuts on the left side of the heart to find the mitral valve, and
aortic seminlunar valve. Or, you can try to cut the rest of the heart in a “frontal” cut, to open it up,
like a book. This cut will best allow you to view the interventricular septum, to appreciate the sizes of
the different chambers, and to view, again, the above structures.
Internal anatomy- chordae tendinae, right and left AV valves (also called the tricuspid and bicuspid,
respectively), right and left semilunar valves (called the pulmonary semilunar, and aortic semilunar
valves, respectively), papillary muscle, trabeculae carnae.
Be able to explain BLOOD flow through the heart and major vessels!!
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Written by Heidi Iverson, Ph.D.