The vomeronasal organ of the rat.

The anatomical organization of the vomeronasal complex of the rat (vomeronasal organ blood vessels, cartilage and glands) and the structure of the vomeronasal organ were studied. This organ is a tubular formation that shows different characteristics along its longitudinal axis. In its rostral portion it has a lateral flattened shape but caudally the organ acquires a typical crescent shape and a greater size. The organ is rotated along its longitudinal axis, the medial wall becoming inferior and the lateral one, superior. In its most caudal portion the organ decreases in size and ends in glandular branches. Three histological segments were recognized in the vomeronasal organ. The rostral one shows a pseudostratified epithelium surrounding all the lumen. The middle segment presents in one of its walls a similar epithelium and, in the other wall, the vomeronasal epithelium. The caudalmost segment shows a simple columnar epithelium that continues with that of glandular ducts. The vomeronasal epithelial border is formed by three types of cellular processes which intermingle, each one showing particular features: (a) microvilli originating from dendrites of bipolar cells; (b) microvilli from supporting cells and (c) micro-processes of undetermined origin. The surface of the vomeronasal epithelium shows an irregular distribution and arrangement of these processes.