Embryology: Development of the Tongue

Development of the Tongue

• The tongue is a muscular organ located in the oral cavity, vital for taste and initial swallowing.
• Development begins around the 4th week of gestation with a medial swelling from the 1st pharyngeal arch called the tuberculum impar.
• By the 5th week, two lateral lingual swellings from the same arch grow, merge, and overlap the tuberculum impar, forming the anterior two-thirds of the tongue.
• The anterior tongue receives sensory innervation from the mandibular branch of the trigeminal nerve (V cranial nerve).

Formation of the Posterior Tongue

• The posterior third of the tongue arises from a median swelling known as the hypobranchial eminence (or copula) originating from the 2nd, 3rd, and 4th pharyngeal arches.
• This area gets sensory innervation from the glossopharyngeal nerve (IX cranial nerve).
• The posterior-most tongue region, associated with the epiglottis, develops from the 4th pharyngeal arch and is innervated by the superior laryngeal nerve.

Musculature of the Tongue

• The connective tissue and blood vessels of the tongue derive from cranial neural crest cells (CNCC).
• Myoblasts responsible for tongue muscles originate from occipital somites, migrating into the tongue primordium.
• Muscle cells receive innervation primarily from the hypoglossal nerve (XII cranial nerve), except for the palatoglossus muscle.

Tongue Anomalies

• Aglossia: Rare congenital absence of the tongue, typically due to severe maldevelopment of the first pharyngeal arches.
• Microglossia (Hypoglossia): An uncommon condition characterized by an abnormally small tongue, leading to restricted muscular movement.
• Macroglossia: Tongue enlargement often associated with congenital syndromes like Down syndrome (trisomy 21).
• Ankyloglossia: Condition resulting from insufficient cellular degeneration, causing an abnormally short lingual frenulum and restricted tongue movement; can range from mild to severe fusion.
• Cleft Tongue (Bifid Tongue): Occurs when lateral swellings fail to merge, leading to a split tongue; can be either partial or complete.