Scanning electron microscopy of ciliary muscle of monkey eye.

The three-dimensional structure of the ciliary muscles of the cynomolgus monkey eye was studied by scanning electron microscopy after the treatment of the muscle in 8 N hydrochloric acid. The meridional muscle bundles in the outer part of the ciliary body were closely arranged and multilayered, extending in a straight anteroposterior direction from its anterior tips to the distal terminal. The anterior part of the muscle bundles consisting of compactly associated small muscle bundles appeared to have a smooth surface and formed a broad belt partially covered by fibrocytes. The anterior tips of the muscle bundles were divided into slender bundles which were connected to the trabecular sheets. The distal terminal part of the muscle bundles tapered markedly in thickness and split into fine bundles resembling a brush, showing a firm fixation in the surrounding stroma of the ciliary body. In the anterior part of the ciliary muscle, the muscle bundles internally situated divided into two branches forming a Y-shape in their extension in the straight anteroposterior direction. The divided branches merged with the branches from other muscles of the same kind and formed muscle sheets with a reticular pattern separated by the stroma of the ciliary body. These adjacent muscle bundles were arranged occasionally like parquetry work, indicating that the sheets appeared to consist of oblique muscles in the meridionally sectioned specimen. In the present study paired tips of V-shape in the anterior part of both the meridional and oblique muscles were not observed. Beneath the obliquely extending muscle bundles, circumferentially arranged muscle bundles were observed, but the interconnection with the other two groups of the muscle bundles was not demonstrated.