File:Bailey250.jpg

Fig. 250. Floor of pharyngeal region of a human embryo of 12.5 mm

His.

The tongue develops from three separate anlagen which unite secondarily.

In embryos of about 3 mm. a slight elevation appears on the floor of the pharynx in the region of the first branchial arch. This is the tuberculum impar, being, as the name indicates, unpaired, and is destined to give rise to the tip and body of the tongue (Fig. 249). Soon afterward two bilaterally symmetrical elevations appear on the floor of the pharynx, which are destined to give rise to the root of the tongue (Fig. 250). These paired elevations, arising in, the region of the second and third branchial arches, gradually enlarge and unite with each other and with the tuberculum impar, leaving between the latter and themselves, however, a V-shaped groove (Fig. 251). At the apex of the groove there is a depression the foramen cecum lingua which is the external opening of the thyreoglossal duct (see p. 301). The groove later disappears, but its position is indicated in the adult by the vallate papillae.

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Pages where the terms "Historic Textbook" and "Historic Embryology" appear on this site, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the interpretation of developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these interpretations may not reflect our current scientific understanding. (More? Embryology History)

Reference

Bailey, F.R. and Miller, A.M. (1921). Text-Book of Embryology. New York: William Wood and Co.

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