FINE STRUCTURE OF SECRETORY CELLS OF UTERUS (SHELL GLAND) OF CHICKEN

The secretory processes in the shell gland of laying chickens were the subject of this study. Three cell types contribute secretory material to the forming egg: ciliated and non‐ciliated columnar cells of the uterine surface epithelium, and cells of tubular glands in the mucosa. The ciliated cells as well as the non‐ciliated cells have microvilli, which undergo changes in form and extent during the secretory cycle. At the final stages of shell formation they resemble stereocilia. It is postulated that the microvilli of both cells are active in the production of the cuticle of the shell. The ciliated cell which has both cilia and microvilli manufactures secretory granules which arise from the Golgi complex in varying amounts throughout the egg laying cycle. Granule production reaches its greatest intensity during the early stages of shell deposition. The ciliated cell probably supplies proteinaceous material to the matrix of the forming egg shell. The non‐ciliated cell has only microvilli. Secretory granules, containing an acid mucopolysaccharide, arise from the Golgi complex. Some granules are extruded into the uterine lumen where they supply the egg shell with organic matrix. Others migrate towards the supranuclear zone. Here a number of them disintegrate. This is accompanied by the formation of a large membraneless space, which is termed “vacuoloid.” Subsequently the vacuoloid regresses and during regression an extensive rough endoplasmic reticulum with numerous polyribosomes of spiral configuration appears. It is suggested that material in the vacuoloid originating from the disintegrating granules is resynthesized and utilized for the formation of secretory product. The uterine tubular gland cells have irregular, frondlike microvilli. During egg shell deposition, these microvilli form large blebs and are probably related to the elaboration of a watery, calcium‐containing fluid. Copyright © 1969 Wiley‐Liss, Inc.