Macroscopic Structure of the Tongue
Anatomically, the organ is divided into three main parts. Anteriorly lies the apex of the tongue (apex linguae), followed by the main bulk, the body of the tongue (corpus linguae), while the posterior section is termed the root of the tongue (radix linguae).
The organ has two distinct surfaces that differ significantly in structure:
- Superior surface, or dorsum of the tongue (dorsum linguae). It features an uneven relief due to numerous papillae. Running right along the midline of the dorsum is the median sulcus of the tongue (sulcus medianus linguae). Further posteriorly lies the sulcus terminalis — an important landmark visually and functionally separating the body of the tongue from its root.
- Inferior surface (facies inferior linguae). Unlike the superior surface, it is completely smooth. The mucous membrane here is very thin and forms a midline fold called the lingual frenulum (frenulum linguae).
Lingual Papillae and Lymphoid Tissue
The mucous membrane of the superior surface contains specialized projections called papillae. There are four types:
- Filiform papillae (papillae filiformes). They densely cover the entire dorsum of the tongue, especially its middle part, giving the surface a characteristic velvety texture. These are projections covered by stratified squamous keratinized epithelium.
- Fungiform papillae (papillae fungiformes). These are small mushroom-shaped elevations rich in taste buds, scattered among the filiform papillae and most numerous at the apex and lateral margins of the organ.
- Vallate papillae (papillae vallatae). These are the largest papillae, numbering between 7 and 11. They are aligned along the boundary between the body and the root of the tongue. Each papilla is surrounded by a specialized moat and groove, with taste buds embedded in the epithelium of its lateral walls.
- Foliate papillae (papillae foliatae). These appear as folds of the mucous membrane along the lateral margins of the tongue. They also contain taste buds and are most prominent in the regions closer to the root.
In addition to the papillae, a large accumulation of lymphoid tissue lies beneath the epithelium at the root of the tongue, known as the lingual tonsil (tonsilla lingualis).
Muscular Apparatus
The tongue is formed by skeletal striated muscle, divided into two major groups based on their attachment points and functions.
Intrinsic muscles of the tongue lack bony attachment points. Their primary role is to alter the shape of the organ:
- M. longitudinalis superior (superior longitudinal) — shortens the tongue and elevates its apex;
- M. longitudinalis inferior (inferior longitudinal) — also shortens the tongue, but depresses the apex;
- M. transversus linguae (transverse) — narrows the tongue;
- M. verticalis linguae (vertical) — flattens the organ.
Extrinsic muscles of the tongue originate on the cranial bones or the hyoid bone and insert into the bulk of the tongue. They alter its position within the oral cavity:
- M. genioglossus (genioglossus) — pulls the entire tongue anteriorly and inferiorly, protruding it;
- M. hyoglossus (hyoglossus) — retracts and depresses the tongue;
- M. styloglossus (styloglossus) — pulls the tongue posteriorly and superiorly;
- M. palatoglossus (palatoglossus) — constricts the fauces upon contraction.
Innervation, Blood Supply, and Lymphatic Drainage
Motor innervation for all tongue muscles is provided primarily by the hypoglossal nerve (n. hypoglossus).
Sensory and taste innervation of the mucosa is divided into two zones:
- Anterior 2/3 of the tongue is innervated by the lingual nerve (n. lingualis) and the chorda tympani (chorda tympani);
- Posterior third receives innervation from the glossopharyngeal nerve (n. glossopharyngeus) and the superior laryngeal nerve (n. laryngeus superior).
Blood supply to the organ is delivered via the lingual artery (a. lingualis). Venous drainage occurs through the corresponding lingual vein (v. lingualis), which ultimately empties into the internal jugular vein (v. jugularis interna).
Lymphatic drainage from the tongue tissues flows into several lymph node groups: submental (nodi lymphoidei submentales), submandibular (submandibulares), and deep cervical nodes (cervicales profundi).