Human Anatomy, Part 1 - K. A. Dyubenko, A. K. Kolomiyytsev, Yu. B. Chaykovsky 2002

Special Part
Splanchnology, splanchnologia [the study of viscera] — Development of the digestive and respiratory systems
Development of the tongue

The mucous membrane of the anterior section of the Tongue (tip and body) derives from the floor of the Oral Cavity, whereas the mucosa of its posterior section (ROOT) originates from the ventral wall of the foregut (pharyngeal gut). The primordia of the mucous membrane appear at the beginning of the 2nd month.

The anterior primordium of the tongue exhibits three swellings (Fig. 276 A). Initially, during the 5th week of embryonic development, proliferation of mesenchymal Cells on the inner surfaces of the right and left mandibular processes gives rise to two lateral lingual swellings. Slightly more caudally, a median unpaired Swelling, the tuberculum impar, develops between them. Posterior to the unpaired swelling, the posterior primordium of the tongue is formed; it is represented by a swelling termed the copula, which connects the ventral ends of the second and third pharyngeal arches (see Fig. 249A-C).

The lateral lingual swellings fuse with each other and with the unpaired swelling to form the body of the tongue, the corpus linguae.

The posterior primordium of the tongue and the adjacent Regions of the second and third pharyngeal arches fuse to form the root of the tongue, the radix linguae. At the junction of the anterior and posterior primordia, a V-shaped groove remains, with its apex directed posteriorly (the terminal sulcus of the tongue, sulcus terminalis). Along this sulcus lie the largest vallate papillae of the tongue, papillae vallatae, while the foramen caecum—a remnant of the thyroglossal duct—is located at the apex. During subsequent development, the tongue increases in length and width, and becomes somewhat demarcated from the floor of the oral cavity due to The formation of deep grooves separating its anterior and lateral parts. According to some data, the musculature of the tongue develops from occipital and cervical myotomes.

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Fig. 276. Diagram of the four stages of tongue development (after Sicher and Tendler).

A — 4-week embryo; B — 5-week embryo; C — embryo at the beginning of the 6th week of development; D — 6 1/2-week embryo. Pharyngeal arches are indicated by Roman numerals: A, B: 1 — lateral lingual swellings; 2 — tuberculum impar; 3 — foramen caecum; 4 — copula; 5 — arytenoid swellings; C, D: 1 — lateral lingual swellings; 2 — tuberculum impar; 3 — foramen caecum; 4 — epiglottis; 5 — rima glottidis; 6 — arytenoid swellings

Major Salivary Glands—the parotid, submandibular, and sublingual glands—begin to develop during the second month of intrauterine life as thickenings of the oral epithelium that subsequently grow into the subepithelial mesenchyme. Repeated branching occurs at the ends of these epithelial cords, resulting in the initial formation of ducts followed by secretory units. The Connective Tissue Components of the glands (the capsule and interlobular connective tissue) develop from the mesenchyme.