2. The LINGUAL PAPILLAE are elevations of the tongue’s mucous membrane that assume various forms and functions. There are four types (filiform, fungiform, foliate, and vallate). Two of which are found in the illustration above.

FILIFORM papillae – are plenty, elongated and conical in shape, and heavily keratinized. This gives their surface a gray or whitish appearance. Additionally, they provide a rough surface that enables the movement of food when chewing. Moreover, among the four types, this type does not have taste buds.

FUNGIFORM papillae – are much less numerous, lightly keratinized, and interspersed among the filiform papillae. They have a mushroom-like shape with well-vascularized and innervated cores of lamina propria. In addition, they have a few taste buds.

Both filiform and fungiform types are elevations of the connective tissue covered by stratified squamous epithelium. The filiform type is pointed while the fungiform is mushroom-shaped.

The other 2 types not seen in the drawing are:

FOLIATE papillae – consist of several parallel ridges on each side of the tongue but are rudimentary (missing) in humans, especially older individuals.

VALLATE papillae – are the largest papillae, with diameters of 1-3 mm. Eight to 12 vallate papillae are normally aligned just in front of the terminal sulcus. Ducts of several small, serous salivary (von Ebner) glands empty into the deep, moatlike groove surrounding each vallate papilla.

3. The ESOPHAGUS is a muscular tube, about 25-cm long in adults, which transports swallowed material from the pharynx to the stomach. The esophageal mucosa has nonkeratinized stratified squamous epithelium, and the submucosa contains small mucus-secreting glands, the esophageal glands, which lubricate and protect the mucosa.