The functional morphology of the human endometrium and decidua

The functional morphology of the human endometrium and decidua has been investigated with particular attention to all aspects of implantation and contraception. The postovulatory triad (of glandular epithelium), comprising subnuclear glycogen, giant mitochondria, and the NCS seems to be involved in both implantation and contraception and has been studied in detail. Initial stages of glycogen formation were found to be related to straight, uncoiled forms of polysomes which, by acting as acceptor molecules for glucose start glycogen synthesis. Discharge of glycogen from the glandular epithelium is achieved by a type of apocrine secretion. Computer-aided reconstruction of giant mitochondria, based on ultra-thin serial sections, revealed that giant mitochondria of the secretory phase of the cycle are not comprised of a single complex mitochondrion, but of numerous single mitochondria. Towards the end of the cycle, these mitochondria either reduce their size to normal by means of budding of protrusions or they are degraded in autophagic vacuoles. The NCS was studied for the first time from the initial stages of formation to the final stages of intracellular degradation. Based on ultra-thin serial sections the NCS was reconstructed with manual and computer-aided reconstruction. It was found to consist of seven sets of tubules, each containing three rows of coiled tubules which are wound in one-and-a-half turns from the site of origin at the nuclear membrane to the karyoplasmic pole. The individual tubules are interconnected by means of lacunae or connecting tubules. The formation of the NCS is suppressed by progesterone IUDs, but not by copper IUDs, and it is not formed in anovulatory cycles or under low-dose gestagen therapy (Minipill). The NCS is believed to participate in regulatory mechanisms of the glandular epithelium. Thus, the contraceptive action of the progesteroneIUD may in part be due to the suppression of the NCS and not only due to decidualization of the endometrial stroma. From the middle to late secretory phase K cells (endometrial granulocytes) and predecidual cells are formed. Their development and ultimate fate was studied during the normal physiological cycle, under a progesterone IUD, and also during pregnancy. K cells do not develop from stromal fibrocytes, as has been postulated in the past, but from lymphocyte-like cells which are present in the endometrium after ovulation. These cells multiply through mitotic division within the endometrial stroma. Under a progesterone IUD and during pregnancy they discharge their secretory granules and reduce their size drastically by giving off glycogen-containing cytoplasmic patches.(ABSTRACT TRUNCATED AT 400 WORDS)