Silicone Modeling of the Interior Spaces of Hollow Organs: Use in Dog and Manatee Respiratory Tract and in a Beef Heart

Abstract

Problem statement: The mechanism, by which the Florida manatee (Trichechus manatus latirostris) vocalizes, remains unknown because the manatee larynx does not contain true vocal cords. Since sound can be generated when air passes through a narrow respiratory structure we needed to visualize the internal anatomy of manatee respiratory tract to locate any candidate regions for study. Approach: To visualize the internal anatomy of upper and lower manatee respiratory tract we have developed a rapid but accurate method of modeling these structures using liquid silicone. We first tested this technique on the respiratory structure of a cadaver dog and then applied it to two small manatees which had died through natural causes. Incisions were made in the trachea of both dog and manatees and commercially available liquid silicone was then forced into the upper and lower respiratory tracts used a slightly modified common automobile grease gun. The animals were then refrigerated overnight and the silicone was allowed to cure for a period of 24 h. Results: In dog, we removed cured silicone model by applying mild force to it after surgically opening the nasal cavity. In the manatees some dissection was necessary for release of mold from the upper nasal cavity, but only mild force was necessary with no dissection to release silicone model from the lower tract. Because the models created exhibited great accuracy and fine structure, including presence of tertiary bronchi in the manatee respiratory tract, we realized that the technique was applicable for use in other hollow organs. We applied this method to the visualization of internal structure of a fresh beef heart and were pleased with the accuracy and detail of model produced. Conclusion: We suggest that this technique can be adopted for three-dimensional visualization of the internal structure and volume estimation of many hollow organs in a wide variety of organisms with both minimal effort and cost.