Fine structure of oviducal epithelium ofXenopus laevis in relation to its role in secreting egg envelopes

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Abstract
During passage through the oviduct, the egg of Xenopus laevis acquires the following substances or envelopes: electron-dense particles in the vitelline coat, the prefertilization layer in and around the vitelline coat, and four layers of jelly. Both gross anatomical observation and light and scanning or transmission electron microscopic observations of various levels of oviduct revealed that the first two are produced in the pars recta 1 and 2 portions, and that jelly layers 1–4 are added in the pars convoluta 1–4 respectively. The relative lengths of these portions were 0–0.044, 0.044–0,055, 0.055–0.52, 0.52–0.70, 0.70–0.87 and 0.87–1.00 from anterior to posterior. Along the whole length of the oviduct, the epithelium was comprised of ciliated cells and various types of secretory cells. Except for the pars recta 1 portion, there were two or three types of secretory cells in each portion of the oviduct, indicating that the structure of each stratum of the egg envelope is formed by an interaction of products from the specific types of secretory cells in each portion of the oviduct.