New Findings in Developmental Studies of Laryngeal Mound With a Reference to Its Attached Structures in Japanese Quail (Coturnix coturnix Japonica).

The laryngeal mound (LM) formed the caudal part of the pharyngeal floor, which varied in position, shape, and length at different ages. This work aimed to study the morphogenesis of the LM in the embryonic and post hatching periods grossly, histologically, and by scanning electron microscopy using forty-eight Japanese quails. The LM primordia appeared on the 8th day of incubation as a raised elevation carried on a deep median symmetrical sulcus (glottis primordium). As a result of rapid differential LM parts growth, LM took different shapes with advanced ages, finally ending in a heart shape. Internally, LM was supported by hyaline laryngeal cartilages; a C-shaped cricoid cartilage that had two wings, paired fork-like two arytenoids, and a comma-shaped procricoid that had four articulations. The glottis appeared as a central longitudinal opening on the 13th day of incubation. With age advancing, it was characterized as a wide rostral commissure and a caudal narrow one that was supported on either side by arytenoid cartilages. Additionally, on the 13th day, a bilateral sagittal row to the glottis developed, consisting of 8-9 small caudally directed papillae. At that time, rostral and caudal transverse laryngeal papillary rows appeared. LM had compound tubuloalveolar submucosal laryngeal glands that were situated between M. dilator glottidis and cricohyoideus and opened on the dorsal surface of LM. Histochemically, the early post-hatching stages of the glandular secretion were PAS-positive while late post-hatching ages had alcinophilic reactions. In conclusion, the LM had rapid morphological developmental events in the early ages other than the adult ages.