Light and Scanning Electron Microscopic Examination of the Chicken Oviduct during the Embryonic and Posthatching Stages

The present study aimed to study the sequence of developing the oviduct of the Alexandria chicken during the embryonic and posthatching period by using the light and scanning electron microscopic (SEM) examination. The Mullerian duct began to appear as left and right urogenital ridges composed of stratified cuboidal epithelium at the ventrolateral aspect of the mesonephros at the 5-day-old embryo. At the 6-day-old embryo, the left urogenital ridge canalized and the tubal wall surrounded a circular lumen composed of three cellular components; inner simple columnar epithelium, multilayers of mesenchymal cells, and outer stratified cuboidal epithelium. At the 8-day-old embryo, the inner tubal layer became composed of simple-to-pseudostratified ciliated columnar epithelium, the density of the mesenchymal cells increased, and the outer layer became simple squamous epithelium at the medial aspect of the duct and stratified epithelium at the lateral aspect of the duct. The left oviduct of the 1-day-old chick resembled the oviduct of 8-day-old embryo except the SEM observations of the tunica mucosa of the 1-day-old chick which showed extensive mucosal folds with many straight cilia. At the 1-week-old chick, the left oviduct showed a folded lumen surrounded by simple columnar ciliated epithelial layer followed by a layer of mesenchymal cells, many layers of smooth muscles surrounded the mesenchymal cells layer and outer simple squamous epithelium layer. At the 1-month-old chick, the left oviduct wall was composed of five layers surrounded by a star-shaped lumen.