Fig. 10
From: Functional morphological study of the choana in different bird species
Photomicrograph of a transverse section of kestrel shows the epithelium roof is keratinized (double arrows) which covers the choanal ridges (Chr), then extends dorsally and changes gradually into pseudostratified ciliated columnar epithelium (arrow). Upper left shows pseudostratified columnar epithelium (Psc) with cilia (head arrow), goblet cell (Gc), and simple alveolar gland (star). (H& E)