Editing Tongue (section)

===Development===
[[File:Gray979.png|thumb|Floor of pharynx at about 26 days showing lateral swellings at first pharyngeal arch (mandibular arch).]]
The tongue begins to develop in the fourth week of [[human embryonic development|embryonic development]] from a median swelling – the [[median tongue bud]] (tuberculum impar) of the [[first pharyngeal arch]].<ref name=Larsen />

In the fifth week a pair of '''lateral lingual swellings''', one on the right side and one on the left, form on the first pharyngeal arch. These lingual swellings quickly expand and cover the median tongue bud. They form the anterior part of the tongue that makes up two-thirds of the length of the tongue, and continue to develop through [[prenatal development]]. The line of their fusion is marked by the [[Tongue#Upper surface of the tongue|median sulcus]].<ref name=Larsen/>

In the fourth week, a swelling appears from the second [[pharyngeal arch]], in the midline, called the [[copula linguae|copula]]. During the fifth and sixth weeks, the copula is overgrown by a swelling from the third and fourth arches (mainly from the third arch) called the [[hypopharyngeal eminence]], and this develops into the posterior part of the tongue (the other third and the posterior most part of the tongue is developed from the fourth pharyngeal arch). The hypopharyngeal eminence develops mainly by the growth of [[endoderm]] from the third pharyngeal arch. The boundary between the two parts of the tongue, the anterior from the first arch and the posterior from the third arch is marked by the terminal sulcus.<ref name="Larsen">{{cite book|last1=Larsen|first1=William J.|title=Human embryology|url=https://archive.org/details/humanembryology0003lars|url-access=registration|date=2001|publisher=Churchill Livingstone|location=Philadelphia, Pennsylvania|isbn=0-443-06583-7|pages=[https://archive.org/details/humanembryology0003lars/page/372 372]–374|edition=Third}}</ref> The terminal sulcus is shaped like a ''V'' with the tip of the V situated posteriorly. At the tip of the terminal sulcus is the [[Tongue#Upper surface of the tongue|foramen cecum]], which is the point of attachment of the [[thyroglossal duct]] where the embryonic [[thyroid]] begins to descend.<ref name=GRAYS2005 />