Human endometrial fluid kinetics as observed by scanning electron microscopy.

Segments of human endometrium, obtained during different stages of the menstrual cycle, were fixed in glutaraldehyde, processed by critical point drying, coated with carbon and gold, than observed with a scanning electron microscope under magnifications varying from 20 to 200,000. The endometrium was basically made of two different types of cells: secretory nonciliated cells and ciliated cells. Different types of secretory cells at different stages of secretory cycles were observed. The endometrial secretion is apocrine: the apical cell membrane of the endometrial cell ruptures, releasing secretory material. The rupture of cells within a given segment of the endometrium is asynchronous. Development of aptical microvilli, synthesis, storage, and release of endometrial secretory granules, and ciliogenesis are hormone dependent. The response of the ciliated and secretory cells of the endometrium varies throughout the menstrual cycle. This is particularly noted in cell specialization, the development of apical microcilli, and ciliogenesis.