Development of the Tongue

Development of the Tongue

The tongue begins development around the 4th week of intrauterine life.

Development can be studied under 3 components:

1. Mucous membrane
2. Muscles
3. Fibrous stroma

🌱 Origin of the Mucous Membrane

• It develops from the endoderm of the floor of the primitive pharynx.

• Divided into two regions:

  • Anterior two-thirds
  • Posterior one-third

These regions have different embryological origins.

🧱 Role of Pharyngeal Arches

During the 4th week, six mesodermal pharyngeal (branchial) arches form.

Mnemonic to Remember Layers from Outside In: CAP:
C: Pharyngeal Cleft – ectoderm
A: Pharyngeal Arch – mesoderm
P: Pharyngeal Pouch – endoderm

👅 Development of Anterior Two-Third of the Tongue

Develops from the first pharyngeal arch, from:

• Two lingual swellings (paired)
• Tuberculum impar (unpaired midline swelling)

These swellings:

• Merge in the midline
• Form the anterior two-thirds
• Are separated from the floor of the mouth by the alveololingual groove

🔹 Foramen Cecum and Thyroglossal Duct

• A depression called the foramen caecum forms behind the tuberculum impar.
• It's a remnant of the thyroglossal duct, which gives rise to the thyroid gland.

👅 Development of Posterior One-Third of the Tongue

Develops from second, third, and fourth arches via:

• A median swelling called the hypobranchial eminence
• Divided into:
  • Cranial part (mostly from the 3rd arch)
  • Caudal part (from 4th arch)

🧩 Key Features:

• The cranial part grows forward, fusing with anterior tongue.
• The line of fusion is the sulcus terminalis.
• The caudal part forms the epiglottis.

📌 Summary of Development

🔌 Nerve Supply of Tongue and Its Developmental Basis

The nerve supply of the tongue reflects its embryological origin.

🔹 Anterior Two-Third

• General sensation: Lingual nerve (branch of V3 – 1st arch, post-trematic)
• Taste sensation: Chorda tympani (branch of facial nerve – 1st arch, pre-trematic)

🔹 Posterior One-Third

• General & taste sensation: Glossopharyngeal nerve (CN IX)
  • Nerve of the 3rd arch

🔹 Epiglottis and Valleculae

• Supplied by internal laryngeal nerve (branch of superior laryngeal nerve, from vagus)
  • Nerve of the 4th arch