Development of the Tongue
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Development of the Tongue
The tongue begins development around the 4th week of intrauterine life.
Development can be studied under 3 components:
- Mucous membrane
- Muscles
- Fibrous stroma
🌱 Origin of the Mucous Membrane
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It develops from the endoderm of the floor of the primitive pharynx.
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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
| Tongue Region | Structure Involved | Pharyngeal Arch | Outcome |
|---|---|---|---|
| Anterior 2/3 | Lingual swellings + Tuberculum impar | 1st arch | Mucosa of anterior tongue |
| Posterior 1/3 | Cranial hypobranchial eminence | 3rd arch | Mucosa of posterior tongue |
| Epiglottis + Valeculae | Caudal hypobranchial eminence | 4th arch | Epiglottis, valleculae area |
🔌 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
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