Fig. 24. Low power TEM of a stage 3 embryo in vitro through the epiblast adjacent to the hypoblast (H). 145-170 hours post-insemination (original magnification x10,800). Note lipid droplets (L) and rough endoplasmic reticulum (RER). The RER is very long in the epiblast cells adjacent to the hypoblast generally running along the long axis of the mitochondria or bridging the cytoplasm between adjacent mitochondria. In some cells a cisternum of RER is closely apposed to the parallel membrane of the Golgi complex. In some regions the RER is continuous with annulate lamellae. Lipid globules are common. Some are closely associated with mitochondria.
(From: Lopata, Kohlman, and Kellow, 1982. Reproduced with permission of the publisher, John Wiley & Sons.)