The circumvallate papillae (or vallate papillae) are dome-shaped structures on the human tongue that vary in number from eight to twelve.
They are situated on the dorsum of the tongue immediately in front of the foramen cecum and sulcus terminalis, forming a row on either side; the two rows run backward and medially, and meet in the midline.
Each papilla consists of a projection of mucous membrane from 1 to 2 mm. wide, attached to the bottom of a circular depression of the mucous membrane (some text referred to as moats); the margin of the depression is elevated to form a wall (vallum), and between this and the papilla is a circular sulcus termed the fossa. The papilla is shaped like a truncated cone, the smaller end being directed downward and attached to the tongue, the broader part or base projecting a little above the surface of the tongue and being studded with numerous small secondary papillÃ¦ and covered by stratified squamous epithelium.
Ducts of lingual salivary glands, referred to as Von Ebnerâ€™s glands empty serous secretion into the base of the circular depression (moats). The function of the secretion is presumed to flush materials from the base of circular depression to ensure that taste buds can respond to changing stimuli rapidly. (Michael H. Ross, Histology: A text and alas 5th edition)
The circumvallate papillae get SVA innervation from cranial nerve IX, the glossopharyngeal nerve, even though they are anterior to the sulcus terminalis. The rest of the anterior 2/3s of the tongue gets SVA innervation from the chorda tympani of cranial nerve VII, distributed with the lingual nerve of cranial nerve V.
The fungiform papillae are mushroom shaped papillae (projections) on the tongue. They are located on the top (dorsal) surface of the tongue, scattered throughout the filiform papilla but mainly at the tip and lateral margins of the tongue. They have taste buds on their superior (upper) surface which can distinguish the five tastes: sweet, sour, bitter, salty, and umami. They have a core of connective tissue. They are innervated by the seventh cranial nerve, more specifically via the submandibular ganglion, chorda tympani, and geniculate ganglion ascending to the solitary nucleus (the sensory component of the Vagus nerve in the brainstem).
Taste-buds, the end-organs of the gustatory sense, are scattered over the mucous membrane of the mouth and tongue at irregular intervals. They occur especially in the sides of the vallate papillae. There is a localized area at the side of the base of the tongue, the foliate papillae, in which they are especially abundant.
The causes of circumvallate papillae may include trauma, infections, lesions on the tongue and lacerations. Circumvallate papillae is a small bump that is on the tongue which is where the taste buds are located