Origin and development of Bruch's membrane in monkey fetuses: an electron microscopic study.

The appearance of the components of Bruch's membrane in staged monkey fetuses was investigated with the electron microscope. The formation of this structure is closely associated with the morphological and cytological changes of the adjoining tissues. The sequence of events in the primate is as follows: (1) establishment of basal lamina of the pigment epithelium on the twenty-seventh day of gestation (optic cup stage); (2) appearance of some aggregated collagen fibers with nodosities on the thirty-eighth day of gestation; (3) layering of some collagen fibers with striations on the forty-sixth day of gestation; (4) appearance of the first immature elastic fibrils on the forty-ninth day of gestation; and (5) incomplete formation of basal lamina of the choriocapillary endothelium on the fifty-fourth day of gestation. The observations are discussed in relation to published work which has a bearing on Bruch's membrane formation.