The fine structure of the tubular glands in the isthmus of the oviduct of the hen
Khairallah, Lamia Haddad
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The histology, histochemistry and fine structure of the tubular glands of the isthmus region of the hen's oviduct were studied during various phases of the egg laying cycle. Numerous tubular glands were found in the lamina propria of the isthmus region. These glands consisted of a single layer of pyramidal epithelial cells. Histochemical studies showed the presence or large secretory granules in the apical region of the cytoplasm of the gland cells. These granules were composed of neutral mucopolysaccharides and sulfur-containing proteins and were especially abundant during active secretory phases of the egg laying cycle. Fine structural studies revealed the presence or an extensive and highly organized endoplasmic reticulum, a well developed Golgi complex, and numerous secretory gramles in the gland cells during an active secretory phase. Within the rough surfaced endoplasmic reticulum, finely granular material and discrete intracisternal granules, 400-800 Å in diameter, were seen. They represented the protein precursors or the definitive secretory granules of the cells. The presence or transitional elements between the endoplasmic reticulum and the small vesicles in the outer region or the Golgi complex indicated that the proteins are concentrated in this region. In addition, the Golgi complex seemed to play a role in the synthesis of the neutral mucopolysaccharides of the definitive secretory granules. This is suggested by the presence of discrete granules, 300 Å in diameter, within the cisternae of the Golgi, the blobs at their ends, and the small vesicles budding from the ends of the cisternae. As they leave the Golgi region, these secretory granules are composed of two components: an electron dense homogeneous component and a component of lower electron density which appeared either finely granular or fibrillar. In the cytoplasm, the granules undergo further elaboration as suggested by the appearance of a third component, the vermiform complex. Each individual complex consisted of a cylindrical structnre, 1000-1300 Å in diameter, of medium electron density, surroumed by an electron dense narrow bard, and having an electron dense core. The definitive secretory granules, consisting of these three components, were 0.5-2.0 micra in diameter. Their mode of discharge into the lumen is merocrine. It is suggested that the proteins and neutral mucopolysaccharides of the secretory granules of the tubular glands of the isthmus are implicated in the formation of the keratin and mucopolysaccharide fibers of the shell membranes of the egg.
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