The development of the tongue is quite complex. Once the structures are mature they remain the same throughout the individual's entire life. The different areas of innervation, taste sensation and motoric function can be extremely confusing and hard to remember. However, upon reading about the embryological development of this particular organ, the structures and their supply hold a deeper logic. A detailed understanding of this structure and its adjacent anatomical structures is essential for many medical professionals and those in related fields.
The first four pharyngeal arches contribute to the development of the tongue in its entirety. Below is a list naming each individual arch, the embryonic structures that it divulges, the adult structures they mature to become and the cranial nerve that innervates that specific arch and all of its structures.
- Arch 1: the embryonic structures that arise from this pharyngeal arch include the bilateral lingual swellings and the tuberculum impar. These structures mature to form the anterior two thirds of the tongue. The general somatic afferent is the lingual branch of the mandibular division of the trigeminal nerve or fifth cranial nerve. The special visceral afferent is the chorda tympani of the facial nerve or the seventh cranial nerve.
- Arch 2: This arch is eventually overgrown by arch three and is not part of the mature adult tongue. A very small remnant of this arch contributes to the hypobranchial eminence. There is no innervation by a cranial nerve since there is no adult structure.
- Arch 3: Along with a small amount of the second arch, this arch produces the embryonic hypobranchial eminence. This eminence eventually becomes the posterior third of the tongue. The general somatic afferent for this arch is the glossopharyngeal nerve and it is the same nerve that applies for the special visceral afferent. The glossopharyngeal nerve is the ninth cranial nerve.
- Arch 4: As a whole, the hypobranchial eminence consists of arches two, three and four. The fourth arch also contributes the epiglottic swelling, the arytenoid swelling and the laryngotracheal groove. These all merge and become the root of the tongue. The internal laryngeal branch of the vagus nerve or the tenth cranial nerve serves as the general somatic afferent. The special visceral afferent is also the exact same nerve.
Anatomy and Supply
The extrinsic and intrinsic muscles of the tongue are formed by the migration of occipital somites mesoderm. It moves anteriorly with the hypoglossal nerve or cranial nerve number twelve. The extrinsic muscles are those that surround the tongue, are directly attached to it and partake in its movement. These muscles include the genioglossus muscle, the hyoglossus muscle, the styloglossus muscle and the palatoglossus muscle. The intrinsic muscles are within the tongue and play a role in every movement of the tongue. Included within the tongue as an individual organ are the transverse fibers, the vertical fibers and the superior and inferior longitudinal fibers of the tongue musculature. For more information of the tongue, its innervation, its blood supply and its functions, please check out kenhub’s online library.
A particular pharyngeal arch defect known as Pierre Robin Syndrome causes Glossoptosis among other symptoms. This particular defect causes the tongue to be displaced posteriorly and may cause airway obstruction or apnea.