Tongue

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 mass — the body of the tongue (corpus linguae), while the posterior section is called the root of the tongue (radix linguae).

The organ has two distinct surfaces that differ significantly in structure:

• Upper surface, or the dorsum of the tongue (dorsum linguae). It has an uneven relief due to the presence of numerous papillae. Directly along the midline of the dorsum runs the median sulcus of the tongue (sulcus medianus linguae). Closer to the posterior sections is the terminal sulcus (sulcus terminalis) — an important landmark that visually and functionally separates the body of the tongue from its root.
• Lower surface (facies inferior linguae). Unlike the upper surface, it is completely smooth. The mucous membrane here is very thin and forms a fold along the midline — the frenulum of the tongue (frenulum linguae).

Lingual papillae and lymphoid tissue

The mucous membrane of the upper surface contains specialized projections called papillae. There are four types of them:

1. Filiform papillae (papillae filiformes). They densely cover the entire dorsum of the tongue, especially its middle part, giving the surface a characteristic velvety appearance. These are projections covered with stratified squamous keratinizing epithelium.
2. Fungiform papillae (papillae fungiformes). They have the shape of small mushroom-like elevations. They are rich in taste buds and are scattered among the filiform papillae, most frequently found at the apex and margins of the organ.
3. Vallate papillae (papillae vallatae). These are the largest papillae, ranging in number from 7 to 11. They are lined up along the border between the body and the root of the tongue. Each such papilla is surrounded by a special circular wall and sulcus, and taste buds are embedded in the epithelium of its lateral walls.
4. Foliate papillae (papillae foliatae). These represent folds of the mucous membrane along the lateral margins of the tongue. They also contain taste buds and are most prominently developed in the areas located closer to the root.

In addition to papillae, a large accumulation of lymphoid tissue is located in the region of the root of the tongue (beneath the epithelium). This formation is called the lingual tonsil (tonsilla lingualis).

Muscular apparatus

The tongue is formed by striated musculature, which is divided into two major groups depending on their points of fixation and functions performed.

Intrinsic muscles of the tongue do not have attachment points on bones. Their main task is to change the shape of the organ itself:

• M. longitudinalis superior (superior longitudinal muscle) — shortens the tongue and elevates its apex;
• M. longitudinalis inferior (inferior longitudinal muscle) — also shortens the tongue, but depresses the apex downwards;
• M. transversus linguae (transverse muscle) — makes the tongue narrower;
• M. verticalis linguae (vertical muscle) — flattens the organ.

Extrinsic muscles of the tongue originate on the bones of the skull or the hyoid bone and insert into the substance of the tongue. They change its position within the oral cavity:

• M. genioglossus (genioglossus muscle) — pulls the entire tongue forward and downward, ensuring its protrusion;
• M. hyoglossus (hyoglossus muscle) — displaces the tongue backward and downward;
• M. styloglossus (styloglossus muscle) — retracts the tongue backward and upward;
• M. palatoglossus (palatoglossus muscle) — constricts the fauces upon contraction.

Innervation, blood supply, and lymphatic drainage

The motor activity of all tongue muscles is provided primarily by the hypoglossal nerve (n. hypoglossus).

Sensory and gustatory innervation of the mucous membrane is divided into two zones:

• The anterior 2/3 of the tongue are innervated by the lingual nerve (n. lingualis) and the chorda tympani (chorda tympani);
• The posterior third receives innervation from the glossopharyngeal nerve (n. glossopharyngeus) and the superior laryngeal nerve (n. laryngeus superior).

Blood supply to the organ is carried out via the lingual artery (a. lingualis). Venous outflow proceeds through the vein of the same name — v. lingualis, which subsequently empties into the internal jugular vein (v. jugularis interna).

Lymph from the tissues of the tongue drains into several groups of lymph nodes: submental (nodi lymphoidei submentales), submandibular (submandibulares), and deep cervical nodes (cervicales profundi).

Class and exam questions

What else to study on this topic

• Histological structure of taste buds and the mechanism of taste perception
• Topography of the lingual artery and Pirogov's triangle
• Formation and functions of the lingual tonsil as part of the lymphoid pharyngeal ring
• Peculiarities of the pathway of nerves innervating the anterior 2/3 and posterior 1/3 of the tongue

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