Three dimensional organization of collagen fibril network of the guinea pig tympanic membrane : Scanning electron microscopic study of the alkali/water treated samples

Three dimensional organization of the collagen fibril network of the guinea pig tympanic membrane was studied by a modified alkali/water maceration method and scanning electron microscopy. The collagen fibril network of the tympanic membrane is formed of the outer radial fibril bundles and inner circular fibril bundles and additional oblique and parabolic fibril bundles. In the lower half of the tympanic membrane, long radial bundles arising from the umbo and the lower two-fifths of the malleus handle spread radially to blend into the fibrocartilageous tympanic ring. In the upper half portion of the tympanic membrane, short radial bundles run antero- or posterosuperiorly almost paralled with each other connecting the upper three-fifths of the handle of the malleus and the tymanic ring. Oblique bundles running oblique against circular bundles were found only in the inferior portion of the tympanic membrane and the parabolic bundles running parabolically aganinst the circular bundles were observed in the antero- and posterosuperior, anterior and posterior portion of the tympanic membrane. The oblique and parabolic bundles merge with the circular bundles in places but with only a few connections with the radial bundles in the outer layer. At the periphery of the tympanic membrane, circular bundles increase in number to form a thick band of collagen fibrils, annular ligament. Beneath the annular ligament, the radial bundles blend with these special circular bundles. The radial and circular bundles are considered to be the main bundles of the tympanic membrane responsible for the mechanical property to the tympanic membrane. The oblique and parabolic bundles seem to strenghen the connection of the radial and circular fibrils forming a collagen network in the connective layer of the tympanic membrane.