Human bilharzial ureters: I. Fine structure of eggs deposited in the submucosa and muscularis.

The internal fine structure of the partially calcified Schistosoma haematobium eggs in the lower ureteral segments of Saudi patients with chronic urinary schistosomiasis is described. The egg shell is penetrated by cribriform pores and consists of the three previously described layers: outer microspinous, middle intermediately dense, and inner dense layers. The space between the egg shell and the developing embryo is partitioned by three layers. An outer acellular Reynolds' layer of unknown origin and function consists of a fribrillar material mixed with a finely granular matrix extending to the egg-shell pores via racemose channels. The middle von Lichtenberg's envelope consists of a single layer of flattened epithelial cells containing several mitochondria as in other previously described Schistosoma eggs suggesting an active, and perhaps selective, transport in or out of the egg shell. The inner fluid filled cavity, or Lehman's lacuna, between the von Lichtenberg's envelope and the embryo contains numerous lipoid bodies suggesting a relation to vitelline cells. Four systems (out of eight previously described for the free, mature Schistosoma miracidium) have been recognized for the first time in the developing miracidium within S. haematobium eggs and include: (1) ciliated epidermal plates representing the epithelial system, (2) an outer circular and an inner longitudinal muscle layer forming the musculatures, (3) lateral penetration glands, and (4) ciliated flame cells representing the excretory system.