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Every human tongue has circumvallate papillae, a series of circular bumps characterized by surrounding moats. The tongue is the major organ for taste, and these structures serve as its taste buds, making it an essential part of the gustatory system. They are also known as vallate papillae.
The circumvallate papillae, usually numbering between eight and 14, are located at the back of the tongue. The area is divided by the median sulcus, and the bumps lay on both halves. At the front are the concavity called the foramen cecum and the sulcus terminalis, named so because this is where the median sulcus ends. This means that there are two rows of papillae.
These tastebuds are usually described as truncated cones about 0.04 to 0.08 inches (1 or 2 millimeters) in size, with their larger ends exposed and the smaller ends attached to the tongue. At their base are circular ditches usually referred to as moats, each of which have walls called vallum. They are actually named after such a feature.
This particular set of circular bumps is considered a protrusion of mucous membrane. This is a lining that can be found in several parts of the body, including the eyelids, ears, mouth, lips and nostrils. The circumvallate papillae are covered by squamous epithelium, a layer of tissue characterized by squamous cells, which are shaped like scales.
The circumvallate papillae are usually associated with Von Ebner's glands, or gustatory glands. Named after 19th-century Austrian anatomist and histologist Anton Gilbert Victor von Ebner, Ritter von Rosenstein, these glands can be found surrounding the papillae. They are known to secrete a digestive enzyme called lingual lipase. When secreted, the lingual lipase enters the ditches and cleanses them to induce a more rapid stimuli response. The enzyme of Von Ebner's glands is also instrumental in the hydrolysis, or decomposition with water, of triglycerides into monoglycerides and free fatty acids.
The vallate papillae is one of the four types of papilla found in the tongue. At the sides of them are the foliate papillae, which resemble leaves in their folded appearance. Ungiform papillae are located at the tongue's tip and sides, and they are named for their distinctive mushroom shape. Although the filiform papillae do not have taste buds, they are the most abundant of the tongue's bumps, resembling V-shaped cones.