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The tongue is an extremely sensitive organ that performs on a complex muscle background. The primary functions of the stomatognathic system, such as mastication, deglutition, and speech, require the active involvement of the tongue. Embryologically, the development of tongue is a very complicated process that starts around the fourth or fifth week of the gestation period, and its development has a marked influence on the oral cavity.

Developmental and structural abnormalities of the tongue are common features. The various morphological variations that may occur during the development of tongue are[5]: Aglossia Microglossia Macroglossia Ankyloglossia Cleft tongue Pentafid tongue Fissured tongue Geographic tongue Hairy tongue Median rhomboid glossitis Aglossia: Congenital absence of the tongue is extremely rare. Usually, the tongue is absent in cases of gross underdevelopment or maldevelopment of the first visceral arches. Microglossia: It is an uncommon developmental condition and is also known as hypoglossia. Its defining feature is a rudimentary or an abnormally small tongue. It leads to limited muscular movement and is associated with syndromes such as Hanhart syndrome. Macroglossia: Macroglossia is an infrequently encountered condition characterized by tongue enlargement, seen in association with other congenital defects leading to syndromes such as down syndrome (trisomy 21), Beckwith-Wiedemann syndrome. Ankyloglossia It occurs due to failure in cellular degeneration leading to a longer anchorage between the tongue and floor of the mouth; this is commonly known as "tongue-tied" and demonstrates an abnormally short lingual frenulum. Ankyloglossia can range in severity from mild to complete ankyloglossia in which the tongue gets fused to the floor of the mouth restricting its free movement.[6] A short lingual frenulum leading to tongue-tie is also associated with several genetic syndromes such as related Robinow syndrome, oral-facial-digital syndrome Type I, Opitz syndrome, and Van der Woude syndrome. Cleft tongue: It is also known as bifid tongue and occurs when the lateral swellings fail to merge. It can be partial or complete. The former is a more common entity and is manifested as a deep groove on the dorsal surface of the tongue in the midline. It occurs when the mesenchymal proliferation interferes with the merging leading to failure of the obliteration of the groove. There are reports of bifid tongue in syndromic cases like Opitz G BBB syndrome, oral-facial-digital syndrome type I, Klippel–Feil anomaly, and Larsen syndrome.[7] Pentafid tongue: Disturbance in the mesodermal penetration and mesenchymal fusion during the development of tongue development is responsible for this malformation.

Cleft tongue: It is also known as bifid tongue and occurs when the lateral swellings fail to merge. It can be partial or complete. The former is a more common entity and is manifested as a deep groove on the dorsal surface of the tongue in the midline. It occurs when the mesenchymal proliferation interferes with the merging leading to failure of the obliteration of the groove. There are reports of bifid tongue in syndromic cases like Opitz G BBB syndrome, oral-facial-digital syndrome type I, Klippel–Feil anomaly, and Larsen syndrome.[7] Pentafid tongue: Disturbance in the mesodermal penetration and mesenchymal fusion during the development of tongue development is responsible for this malformation. Fissured tongue: It is also known as scrotal tongue or lingua fissurata. It is congenital anomaly manifested as grooves oriented anteroposteriorly on the dorsal aspect of the tongue with multiple branches extending towards the lateral aspect. The grooves range from 2 to 6 mm in depth. In a severe form of the fissured tongue, when the grooves are extremely prominent and interconnected, the tongue may appear to be lobulated. It can also present in association with down syndrome or Melkerson-Rosenthal syndrome (a triad of fissure, granulomatous cheilitis, and cranial nerve VII paralysis). Geographic tongue: Geographic tongue, also known as lingua geographica or benign migratory glossitis is an inflammatory disorder caused by loss of filiform papillae. Hairy tongue: It is also known as a black hairy tongue and characteristically demonstrates the accumulation of excess keratin on the filiform papillae on the dorsal surface of the tongue leading to the formation of elongated strands resembling hair. This condition most commonly affects the midline just anterior to the circumvallate papillae, usually sparing the lateral and anterior borders. Median rhomboid glossitis: It is a condition that presents in the midline of the dorsal surface of the tongue, just in front of the circumvallate papillae. It presents as a well-demarcated, symmetric, depapillated area. However, it also occasionally appears in the paramedial location.