Rat Respiratory System

            Earlier in this laboratory, you made an incision along the midline on the ventral side of the rat. If you have not already cut through the rib cage, do so at this time. Use your scissors and start at the base of the rib cage near the diaphragm and progress cranially to the lower jaw. Be careful, many glands, blood vessels, and organs lie just under the skin and may be damaged if you cut too deeply. Spread the rib cage and expose the organs of the thoracic cavity and the organs in the neck region. When this is completed, the heart will be visible in the center of the cavity. Locate the lungs located on each side of the heart. The membrane lining the wall of the thoracic cavity is the parietal pleura; the membrane covering the lungs is termed the visceral pleura.  There is one lobe to the left lung and four lobes on the right lung (cranial lobe, medial lobe, caudal lobe and accessory lobe) (Figure 16). Just caudal to the lungs, you should be able to see a diaphragm, a thin muscular sheet. 

              Locate the trachea, which is a long tube supported with cartilaginous rings to prevent collapse as the organism inhales. Follow the trachea posteriorly to the point at which it branches into a right and left bronchus.  These bronchi lead to the lungs where they branch further into bronchioles (Figure 16).

            Follow the trachea anteriorly and locate the larynx (the larynx is visible in Figure 22) ,. It should appear as an enlarged, square-shaped “box”. The larynx allows mammals to have a vast repertoire of sounds ranging from ultrasonic squeaks and chirps (in bats) to the highly complex sounds of human speech.

Figure 16: Diagram of the respiratory system.