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frenulum of tongue
The frenulum of tongue or tongue web (also lingual frenulum or frenulum linguæ) is a small fold of mucous membrane extending from the floor of the mouth to the midline of the underside of the tongue.
==Development==
The tongue starts to develop at about 4 weeks. The tongue originates from the first, second, and third pharyngeal arches which induces the migration of muscles from the occipital myotomes. A U-shaped sulcus develops in front of and on both sides of the oral part of the tongue. This allows the tongue to be free and highly mobile, except at the region of the lingual frenulum, where it remains attached. Disturbances during this stage cause tongue tie or ankyloglossia. During the sixth week of gestation, the medial nasal processes approach each other to form a single globular process that in time gives rise to the nasal tip, columella, prolabium, frenulum of the upper lip, and the primary palate. As the tongue continues to develop, frenulum cells undergo apoptosis, retracting away from the tip of the tongue, and increasing the tongue's mobility.
During early gestation (as early as 4 weeks) the lingual frenulum serves as a guide for the forward growth of the tongue. After birth the tip of the tongue continues to elongate, giving the impression of the frenulum retracting, though in reality this has been going on for some time before birth. This is what gives the impression that the frenulums of some previously tongue-tied infants will "stretch" with age and growth. In reality the tongue often just grows beyond the frenulum, although some do also stretch and/or rupture after mild accidents. Many others continue to cause problems throughout life, unless corrected.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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