The Study of Histogenesis of Sheep Fetus Iris

Abstract

In this study, for determination of histogenesis of iris in sheep, 32 samples of sheep fetuses at different and certain ages were used. After sample preparation and fixation, their age were determined and histological and anatomical studies were done. In histological studies, the H&E staining and two other specific staining (verhoeff and Masson's Trichrome) were used. Obtained results demonstrated that a two-layered cup formed in first month but iris separation from the anterior and ceca part of retina occurred in second month. The separation of iris from ciliary body was completed in third month. From the beginning of third month, the iris formed changes and its circular shape changed to oval form so that its internal angle was larger than its external angle and this condition was retained until the end of pregnancy. General shape of pupil conformed to general shape of iris. It was histologically revealed that iris was formed from the anterior part of the optic cup just at the connection place of outer and inner layers in second month and thereafter a part of superficial ectoderm and choroid was added to it. The first signs of elastic fibers in iris as well as smooth muscles appearance were significant in second month. The posterior cells are pigmented from the beginning of the iris cell formation. Anterior epithelial tissue of the iris was simple squamous and two layer cuboidal cells formed its posterior epithelium which were stabilized in third month. The number of collagen and elastic fibers and smooth muscles and their size increase with age.