In vivo production of nucleolar channel system in human endocervical secretory cells.

Human endocervical mucosa taken from the proliferative, ovulatory and secretory phases of the menstrual cycle in normal fertile women and those after administration of norethiosterone acetate for contraception was studied by electron microscopy. The fine structure of secretory cells, with special reference to the secretory granules and nucleolar differentiation, has been described and discussed. The 'nucleolar channel system' has been observed for the first time in the endocervical nucleolus in the proliferative phase of the menstrual cycle.