Sensory nerve endings in the hard palate and papilla incisiva of the rhesus monkey

The sensory innervation of the hard palate of the rhesus monkey was studied by light and electron microscopy, The mucosa of the hard palate is subject to a particularly heavy mechanical load requiring functional specialisatio n of the horny epithelium in the form of thickenings - the papilla incisiva and eight pairs of rugae palatinae, A thin layer of firm connective tissue (lamina propria) attaches the mucosa to the periost of the hard palate. Se nsory nerve fibres were found most abundantly in the papilla incisiva and f irst rugae palatinae. Their number decreases in an aboral direction. Five t ypes of sensory nerve endings were found. Free nerve endings were ubiquitou s in the epithelium and lamina propria. Merkel nerve endings were found in the basal layer of the epithelium of the papilla incisiva and rugae palatin ae. Meissner corpuscles were located in the connective tissue between epith elial pegs, while lamellated corpuscles were seen below the epithelial pegs . Ruffini corpuscles were found in the deeper layer of the lamina propria. Thus, a variety of sensory nerve endings were found in the hard palate, esp ecially in those areas that are in close contact with the tongue during che wing of food. This rich innervation suggests an important role in monitorin g the mechanical properties of food and the position of the tongue.