DEVELOPMENT OF THE THYROID-GLAND IN THE RAT FETUS INVIVO - AN ULTRASTRUCTURAL AND AUTORADIOGRAPHIC STUDY

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  • 1 January 1980
    • journal article
    • research article
    • Vol. 69  (2) , 91-108
Abstract
A study of the differentiation of the thyroid follicles was carried out in rat fetuses between day 14 of pregnancy, when cellular polarization begins, and day 18, when completely formed follicular lumina are differentiated. After day 18, only the shape and the size of the lumina undergo modifications. The mechanism of folliculogenesis involves the participation of several structures. At 14 days of pregnancy, adherens-type contact zones with membrane densification appear between the cells. These junctional zones spread out and form infoldings which deeply penetrate the cytoplasm. Golgi vesicles migrate to these zones, and fuse among themselves and with the contact membranes: follicular cavities result which can be recognized as soon as day 16 of pregnancy. A radioautographic study showed the beginning of iodide organification at 17 days 11 h of pregnancy. From this time onward Ag grains were seen over the follicular cavity, even if it is still incompletely formed.