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The thoracic cavity lies dorsal to the pectoral muscles. To expose the thoracic cavity two incisions are made on either side of the sternum (Figures 1-2).
Reflect the ribs and note the membranous septum (arrow) that divides the cavity into right and left sides. The posterior region of the thoracic cavity is formed by the muscular diaphragm (arrow). The heart (arrow) lies in the fat filled septum. As seen in a ventral view the lungs fold ventrally toward the heart (Figures 3-4).
A closer look at the right lung reveals that is composed of three major lobes:
The left lung is also composed of three major lobes, but it lacks an accessory lobe.
Examine the relationship between the heart and lungs (Figures 17).
Examine the circulation on the right side of the heart (Figures 18-19). The right side of the heart receives blood low in oxygen from the:
The blood then travels toward the lungs through:
Examine the circulation on the left side of the heart (Figures
The white arrow indicates angle along which the right and left ventricle are seperated by a thick septum. Begin with the structures on the right side of the heart:
Blood is oxygenated in the lungs before returning to the heart in the pulmonary vein which is not clearly shown. Oxygenated blood flows through:
Also note the fat body (11) lying across the base of the aorta.
By reflecting the left lungs over the heart it is possible to see the trachea (white arrows), which splits before entering the left medial and accessory lobes of the lung.