Development of the Tongue

• Embryonic Stage: The lecture discusses the development of the tongue around the fourth week of embryonic development, marked by present limb buds.

• Pharyngeal Arches: The embryo consists of five pharyngeal arches that play a crucial role in tongue development.

  • First Arch: Mandibular arch.

  • Second Arch: Hyoid arch.

  • Third Arch: Thyrohyoid arch.

  • Fourth and Sixth Arches: Unnamed, paired.

Anatomy Overview

• The pharyngeal arches are essential for forming various structures.

• Inner structures (endoderm) form mucous membranes and glands.

• Key structures in tongue development:

  • Lateral Lingual Swellings: Two swellings representing the sides of the tongue, derived from the first arch.

  • Tuberculum Impar: Medial swelling of the first arch.

  • Copula: Major middle swelling formed from the second, third, and fourth arches.

Laryngeal Inlet and Gut Tube

• The laryngeal inlet leads to the branching pathways of the pharyngeal lung bud and the gut tube.

• Endoderm derivatives line these structures.

• Sulcus Terminalis: Key anatomical landmark, with a midpoint called the foramen cecum.

Adult Structure of the Tongue

• At a later stage, the tongue develops an adult-like structure, identifiable through its anatomical areas and innervation.

• Anterior Two-Thirds: Derived from the first pharyngeal arch, supplied by the mandibular branch of the trigeminal nerve (V3) via the lingual nerve.

• Tonsils: Located in the second arch area, representing its only derivative in the tongue.

• Posterior One-Third: Comes from the third arch, innervated by the glossopharyngeal nerve (taste and general sensation).

Sensory and Motor Innervation

• Anterior Tongue Sensation:

  • General Sensory: From the lingual nerve (V3).

  • Special Sensory (taste): From the facial nerve via chorda tympani.

• Posterior Tongue Sensation: Entirely supplied by the glossopharyngeal nerve.

• Epiglottis and Vallecula: Structures derived from the fourth arch, innervated by the vagus nerve (specifically, the superior laryngeal branch).

• Motor Innervation: Primary motor control comes from the hypoglossal nerve (cranial nerve XII), which is derived from occipital somites.

Development of the Thyroid

• The thyroid development is simpler but occurs in conjunction with the development of the gut tube.

• Important structures involved include the endoderm lining of the gut tube and their relationship to the tongue as the throat develops.