Learning Objective: To describe the anatomical structure, muscular components, innervation, vascular and lymphatic supply, embryological development, and clinical relevance of the tongue.
The tongue is a muscular organ situated on the floor of the oral cavity. It plays essential roles in taste, speech, and the initiation of swallowing (deglutition). Anatomically, it is divided into the anterior two-thirds (oral part) and the posterior one-third (pharyngeal part).
Musculature of the Tongue
Intrinsic Muscles
These muscles are contained entirely within the tongue and are responsible for changing its shape during speech and swallowing.
- Muscles: Superior longitudinal, inferior longitudinal, transverse, and vertical.
- Function: Alter the shape and size of the tongue (e.g., rolling, flattening).
- Innervation: Hypoglossal nerve (CN XII).
Extrinsic Muscles
These muscles originate outside the tongue and insert into it, responsible for gross movements such as protrusion, retraction, elevation, and depression.
| Muscle | Origin | Insertion | Function | Innervation |
|---|---|---|---|---|
| Genioglossus | Mandibular symphysis | Hyoid bone and tongue | Protrudes and depresses the tongue | CN XII |
| Hyoglossus | Hyoid bone | Lateral tongue | Depresses and retracts the tongue | CN XII |
| Styloglossus | Styloid process (temporal bone) | Lateral tongue | Retracts and elevates the tongue | CN XII |
| Palatoglossus | Palatine aponeurosis | Tongue | Elevates posterior tongue | Vagus nerve (CN X) |
Innervation of the Tongue
The tongue receives motor, sensory (touch, temperature, pain), and special sensory (taste) innervation.
| Region | General Sensation | Taste | Motor |
|---|---|---|---|
| Anterior 2/3 | Lingual nerve (CN V3) | Chorda tympani (CN VII) | CN XII (except palatoglossus) |
| Posterior 1/3 | CN IX (glossopharyngeal) | CN IX (glossopharyngeal) | CN XII (except palatoglossus) |
| Epiglottic region | CN X (vagus) | CN X (vagus) | CN X (palatoglossus) |
Vasculature
- Arterial supply:
- Primarily from the lingual artery (a branch of the external carotid).
- Additional contribution from the tonsillar branch of the facial artery.
- Venous drainage:
- Lingual veins → Internal jugular vein.
Lymphatic Drainage
| Region of Tongue | Primary Nodes | Secondary Drainage |
|---|---|---|
| Tip and anterior part | Submental nodes | Deep cervical nodes |
| Lateral anterior 2/3 | Submandibular nodes | Deep cervical nodes |
| Posterior 1/3 | Directly to the deep cervical nodes | — |
Embryological Development
- Develops from the first four branchial arches.
- First arch forms the anterior 2/3, hence CN V3 (lingual nerve) supplies general sensation.
- The second arch contribution is overgrown but explains taste via CN VII (chorda tympani).
- The third arch forms the posterior 1/3, giving CN IX sensory and taste supply.
- The fourth arch contributes to the most posterior tongue and CN X supply.
- The median sulcus marks midline fusion.
- The sulcus terminalis separates the anterior and posterior parts.
- The foramen cecum represents the origin of the thyroid gland—its downward migration forms the thyroglossal duct.
- Persistence of this duct may lead to a thyroglossal cyst or fistula.
Clinical Relevance
Tongue-Tie (Ankyloglossia)
- Caused by the incomplete apoptosis of the lingual frenulum.
- Restricts tongue movement, causing speech or feeding difficulties in infants.
- Managed by frenotomy (surgical release).
