[Ultramicroscopic studies on the human corpus luteum menstruationis and graviditatis]

In high active steroid producing cells of the human corpus luteum we can find in the cytoplasm a well developed smooth endoplasmic reticulum in form of smooth tubules and homogenously spread vesicles resulting from an active metabolic process. We also find specific concertinalike folded membrane complexes which too belong to the endoplasmic reticulum. Numerous mainly tubular mitochondria contain dense lipoid inclusions. Their close conection with the endoplasmic vesicles is expression of a direct interaction of both cell organelles in progesterone production. The transport of the intracellular formed steroid hormones to the capillary takes place via locally enlarged intercellular spaces which communicate with the pericapillary space. On the other hand there are pericellular canaliculi which are coated with a membrane. They have no direct connection to the pericapillar space.