Many studies have been carried out to investigate the morphological structure of the syrinx in many bird species. However, the cellular
organization of the syrinx in the fowls and pigeons is still unclear. The current study revealed that in fowl and pigeon, the syrinx is formed
of three main parts including tympanum (cranial) part, intermediate syringeal part, and bronchosyringeal (caudal) part, in addition to pessulus and tympaniform membranes. A great variation in the structural characteristics of syrinx of fowl and pigeon was recorded. In fowl, the
tympaniform membranes showed a characteristic distribution of elastic and collagen fibers which increase the elasticity of tympaniform
membranes. Moreover, the bony pessulus helps the medial tympaniform membranes to be stiffer, vibrate more strongly so that louder
sound will be generated. In pigeon, the lateral tympaniform membrane is of greater thickness so that the oscillation of this membrane
is reduced and the amplitude is lower. Moreover, the pessulus is smaller in size and is formed mainly of connective tissue core (devoid
of cartilaginous or bony plates), resulting in the failure of stretching and vibrating of the medial tympaniform membranes, that leads to
the generation of deeper sound. Electron microscopic examination of the syringes of fowls and pigeons revealed numerous immune
cells including dendritic cells, plasma cells, mast cells, and lymphocytes distributed within syringeal mucosa and invading the syringeal
epithelium. Telocytes were first recorded in the syrinx of fowls and pigeons in this study. They presented two long telopodes that made
up frequent close contacts with other neighboring telocytes, immune cells, and blood capillaries.