Download Rat Dissection-Circulation

Rat Dissection Guide – Circulatory system
1. Open the thoracic cavity by extending your original cut up the midline from the abdomen to the thorax up to
the base of the neck. Make a second cut along the base of the neck. Pull the skin out to the sides and pin if
necessary.
2. Cut through the rib cage just lateral to the sternum. Keep the cut superficial to avoid injuring the major
vessels. You have just cut into the pleural cavity, yet another body cavity or coelom. This body cavity houses
the heart and lungs.
3. Spread open the chest cavity and look at the diaphragm muscle that separates the thoracic and abdominal
cavities.
4. Find the heart in the center of the thoracic cavity. Determine the apex (the pointed, ventral end) and the base
(the broad, dorsal end). The apex is usually free within the pericardium, and the base contains the great vessels
and the attachment of the pericardium. The pericardium or pericardial sac is a double-layered closed sac that
surrounds the heart and anchors it.
5. The aorta and pulmonary artery are the two largest vessels at the base of the heart. Both have rubbery
white gray walls a few millimeters thick. Both are fastened to each other near the middle and both curve
sharply. The aorta emerges from the center of the base of the heart (from the left ventricle) and is whiter than
the pulmonary artery. The pulmonary artery emerges at the edge of the heart, from the right ventricle.
6. The vena cava and the pulmonary veins are also embedded within the fibrous tissue, but they are thinner
and often are collapsed, so they are more difficult to see. Look for the vena cava as a thin-walled, but large
diameter, bluish or dark red tube.
7. On either side of the base of the heart are thin, wrinkled, darker red chambers that extend into loose flaps.
These are the left atrium and right atrium.
8. Use the diagrams below to help you locate the following structures in your rat:
Arteries: aortic arch, R & L common carotid, subclavian, brachio-cephalic (innominate), thoracic aorta,
abdominal aorta, , renal, R & L common iliac
Veins: posterior & anterior vena cava, R & L external and internal jugular vein, hepatic portal vein, R & L renal
vein
Notes:
a) You will now be able to locate the esophagus, which lies dorsal to the trachea in the thoracic cavity.
b) In order to locate many of these structures, you will need to move other organs in the abdominal cavity out of
the way. Take a few minutes to refresh your memory of the organs of the digestive system while you are
moving them.