Hermida, G.N. and Farías, A. 2009. Morphology and histology of the larynx of the common toad Rhinella arenarum (Hensel, 1867) (Anura, Bufonidae). -Acta Zoologica (Stockholm) 90: 326-338The structure of the larynx of the toad Rhinella arenarum was exhaustively studied. The laryngeal skeleton consists of three bilaterally symmetrical cartilages: the cricoid and two arytenoids. Internally, each half-larynx has an anterior and a posterior chamber. The first chamber is delimited by the epithelium covering the arytenoid cartilage and the anterior membrane. The latter consists of fibro-elastic tissue and contains blood capillaries that, judging by their location and distribution, might serve to maintain vocal cord turgidity. At the level of the cricoid cartilage, two structures are reported here for the first time: the posterodorsal and the anteroventral processes. Both processes are associated with the insertion of the posterior membrane. A cartilaginous rod is located at the free margin of the posterior membrane. This rod appears to support the membrane when the air flows. The distal portion of the larynx communicates with the proximal region of the lung. The epithelium of the laryngeal mucosa contains ciliated cells, goblet cells, secretory cells with short microvilli and neuroendocrine cells immunopositive to PGP 9.5. The results obtained in this study provide new information about the internal organization of the larynx in anurans, which could serve as additional morphological characters for phylogenetic relationships.
Electron microscopy of the lungs of Melanophryniscus stelzneri stelzneri (Anura) revealed the presence of a complex pattern of corpuscular cells (CCs). The respiratory surface over the septa presents small areas where the CCs are grouped forming neuroepithelial bodies (NEBs). These corpuscular structures can also be localized in the inner layer of the lung wall. Although in both cases NEBs protrude slightly into the airway lumen, they are separated from the airway lumen and the basal connective tissue by thin apical and basal cytoplasmic processes of neighbouring pneumocytes. Ultrastructurally, the CCs possess a large nucleus, clear cytoplasm and vesicles of variable morphology and size, containing an electron dense material surrounded by a lucent space in some cases. The size of these dense-core vesicles (DCVs) ranged from 40 to 100 nm. The NEBs are associated with afferent and efferent terminal nerves. These types of nerve endings are located between the CCs and in the basal part of the NEBs. The location of the NEBs in strategic positions on the septa and in the wall of the lung, the presence of the DCVs in the basolateral region of the CCs, the occurrence of synaptic contacts between nerve endings and the CCs and the occurrence of capillaries close to the NEBs, suggest a receptosecretory function for NEBs in the lung of M.s. stelzneri.
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