The dorsum is divided into anterior oral and posterior pharyngeal regions by a V-shaped line, or sulcus terminalis. Īnatomically, the tongue consists of a root, an inferior surface and a dorsum, and is divided into bilateral halves through the presence of a midline fibrous septum. The significant morphological variation seen in the tongues of vertebrates is reflective of multiple adaptive responses to different environmental conditions experienced by these organisms. In some species, it also plays important secondary roles in the capture of prey, regulation of body temperature and grooming. It performs a number of functions that make it an essential contributor for normal mastication, deglutition, general sensation, taste, oral cleansing and vocalization. The mammalian tongue is a large and highly mobile muscular organ that occupies the oral cavity and upper pharynx in most vertebrates. We also survey the clinical presentation of tongue anomalies seen in human populations, whilst considering their developmental and genetic etiology. Here, we present an overview of the gross anatomy and embryology of mammalian tongue development, focusing on the molecular processes underlying formation of the musculature and connective tissues within this organ. These anomalies can range from an absence of tongue formation (aglossia) through to diminutive (microglossia), enlarged (macroglossia) or bifid tongue. In humans, a number of congenital abnormalities that affect gross morphology of the tongue have also been described, occurring in isolation or as part of a developmental syndrome, which can greatly impact on the health and well-being of affected individuals. In particular, there is now evidence that the Hedgehog, TGF-Beta, Wnt and Notch signaling pathways all play an important role in mediating appropriate signaling interactions between the epithelial, cranial neural crest and mesodermal cell populations that are required to form the tongue. Although the gross embryological contributions to tongue formation have been known for many years, it is only relatively recently that the molecular pathways regulating these processes have begun to be discovered. The vertebrate tongue is a complex muscular organ situated in the oral cavity and involved in multiple functions including mastication, taste sensation, articulation and the maintenance of oral health.
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