The normal shape of the trachea is variable and can have different configurations at multiple levels. In a study by Gamsu and Webb,1 looking at different tracheal shapes by computed tomography, it was documented that the most common configuration was round or oval. Less common shapes were horseshoe with flat posterior tracheal membrane, inverted pear, and almost a square. Many abnormal deformities can also exist, one of which is "saber-sheath" trachea."Saber," literally, as stated in Encarta 2001, is "a heavy cavalry sword with a slightly curved blade that is sharp on one edge." This term was first used in late 17th century, from the French sabre, from obsolete German Sabel, of uncertain origin: perhaps from Slavic or Polish szabla, Russian sablya, or from Hungarian szablya. "Sheath" is "a close-fitting covering or a case for the sward."
展开▼
