Comparative Morphological Features of Syrinx in Male Domestic FowlGallus gallus domesticusand Male Domestic PigeonColumba livia domestica: A Histochemical, Ultrastructural, Scanning Electron Microscopic and Morphometrical Study

Abstract

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.

Anatomical, Histological, and Electron Microscopic Structures of Syrinx in Male Budgerigars (Melopsittacus undulatus)

“…For example, mast cells are observed along the lamina propria–submucosa under the tympanum epithelium. Also, the mast cells are recorded in fowls syrinx in our previous study (Ibrahim et al, 2020). Marshall & Dawicki (2007) found that these cells play an important role in tissue microenvironment as they released several mediators.…”

“…The histological features of the syrinx have been described in several bird species by many authors (Yildiz et al, 2003(Yildiz et al, , 2005Frank et al, 2007;Yilmaz et al, 2012;Keskin & Ili, 2013;Ibrahim et al, 2020). However, the cellular elements and the fine structure of the budgerigar syrinx are not fully understood.…”

An investigation of syrinx morphometry and sound frequency correlation during the chirping period in lovebirds (Agapornis fischeri)

“…Tympaniform membranes lateral are functional membranes that produce melodic sounds in the Psittacidae family. 29 The development of the tympaniform membranes lateral is triggered by the development of the chirping sound. The rapid development that occurs in pubertal birds will then decrease gradually at aged 9 mo.…”

Telocytes and their structural relationships with surrounding cell types in the skin of silky fowl by immunohistochemistrical, transmission electron microscopical and morphometric analysis

“…In previous studies, TCs were identified as a novel type of interstitial cells and have been described in various organs of different vertebrates, especially in the human and rodents ( Cretoiu and Popescu, 2014 ). In birds, TCs were also observed in several organs, such as ileum, spleen, trachea, oviduct, and syrinx ( Yang et al., 2015 , 2017 ; Ibrahim et al., 2020 ; Mokhtar and Hussien, 2020 ; Mustafa and El-Desoky, 2020 ). These studies have demonstrated that the morphological characteristics of avian TCs are similar to those of other animal organs.…”

“…Avian TCs made up frequently close contacts with neighboring cell types/structures, such as immune cells (including mast cells and macrophages), smooth muscle cells, nerve fibers and blood vessels. Based on the appearance of direct homocellular contacts between Tps (Tps with Tps, Tps with cell bodies), heterocellular contacts between Tps and neighboring cell types/structures, and the release of shedding vesicles (including exosomes), which act as molecular complex intercellular signaling organelles, avian TCs may be implicated in intercellular signaling ( Ibrahim et al., 2020 ). Subsequently, avian TCs were suggested to regulate the physiological functions of surrounding cell types by direct/indirect contacts and shedding vesicles.…”