Floor of the oral cavity
The floor of the oral cavity (diaphragma oris) is formed by the mylohyoid muscle (m. mylohyoideus), which spans from the mandible to the hyoid bone. The root of the tongue rests on this muscular base.
Beneath the mucosa of the oral floor lies a complex of anatomical structures. Here are the sublingual salivary glands (gll. sublinguales), over which the mucosa forms the corresponding folds (plicae sublinguales). In the medial part of the floor, closer to the mandible, is the sublingual caruncle (caruncula sublingualis). This is an important structure because the ducts of the submandibular and sublingual salivary glands open directly onto it.
In the posteroinferior region, between the mylohyoid and hyoglossus (m. hyoglossus) muscles, run the hypoglossal nerve (XII pair) and the lingual vein. Slightly above them lies the duct of the submandibular gland.
Structure of the tongue
The tongue (lingua) consists of intrinsic muscles, located in three perpendicular planes, and extrinsic muscles extending from bones. The latter include the genioglossus (m. genioglossus), styloglossus (m. styloglossus), and hyoglossus (m. hyoglossus) muscles.
The mucous membrane of the tongue has a varied structure:
- On the dorsal surface (back), it is firmly fused with the muscles.
- On the inferior surface, the mucosa is loosely attached due to abundant adipose and connective tissue. Along the midline here is the frenulum (frenulum linguae), flanked by fimbriated folds, with large lingual veins showing through.
On the dorsum of the tongue, there is a V-shaped sulcus (sulcus terminalis) separating the body from the root. Anterior to the sulcus are the taste vallate papillae (papillae vallatae), as well as filiform, conical, and fungiform papillae. Foliate papillae are located on the edges of the tongue. There are no papillae on the root of the tongue, but its surface is nodular due to the accumulation of lymphoepithelial tissue—the lingual tonsil (tonsilla lingualis).
Blood supply and innervation
Blood supply to the tongue is provided by the lingual artery (a. lingualis). It penetrates the floor of the oral cavity from the inner side of m. hyoglossus and heads toward the tip of the tongue, giving off dorsal branches and the deep lingual artery. The lingual vein accompanies the artery but then runs along the outer side of m. hyoglossus together with the hypoglossal nerve. Thus, the muscle separates the artery (internally) and the vein with the nerve (externally).
Innervation of the tongue is complex:
- Motor: all muscles of the tongue are innervated by the hypoglossal nerve (n. hypoglossus, XII pair).
- Sensory (anterior 2/3): general sensation is supplied by the lingual nerve (n. lingualis from the V pair), and taste sensation by the chorda tympani (chorda tympani from the VII pair).
- Sensory (posterior 1/3): glossopharyngeal nerve (n. glossopharyngeus, IX pair).
- Root of the tongue (near the epiglottis): internal branch of the superior laryngeal nerve (from the X pair). Damage to this nerve can lead to food aspiration.
Lymphatic drainage
Lymphatic fluid drains from the tip of the tongue along the frenulum into the submental lymph nodes (nodi submentales), and then into the submandibular and deep cervical nodes. From the lateral surface of the body, lymph goes directly to the submandibular nodes. From the root of the tongue and the lingual tonsil, lymphatic drainage flows directly into the deep cervical lymph nodes.
Briefly: answers to topical questions
What branches does the lingual artery give off within the floor of the oral cavity and the tongue?
The lingual artery (a. lingualis) gives off the following branches:
- Sublingual artery (a. sublingualis) — supplies the tissues of the floor of the oral cavity and the salivary glands.
- Deep lingual artery (a. profunda linguae).
- Dorsal branches of the tongue (rr. dorsales linguae) — numerous branches within the thickness of the tongue.
The submental artery (a. submentalis) may branch off from the facial artery.
What intrinsic muscles of the tongue are distinguished and how are they arranged?
The intrinsic muscles of the tongue are arranged in three mutually perpendicular planes and are responsible for changing its shape. The following muscles are distinguished:
- Superior longitudinal muscle (m. longitudinalis superior) — shortens the tongue, elevates its apex.
- Inferior longitudinal muscle (m. longitudinalis inferior) — shortens the tongue, depresses its apex.
- Transverse muscle of the tongue (m. transversus linguae) — narrows the tongue.
- Vertical muscle of the tongue (m. verticalis linguae) — flattens the tongue.
What fascial spaces/cellular spaces are distinguished in the region of the floor of the oral cavity?
In the region of the floor of the oral cavity and the root of the tongue, the following cellular spaces and accumulations are distinguished:
- Cellular tissue between the genioglossus muscles.
- Cellular space of the root of the tongue — bounded superiorly by the intrinsic muscles of the tongue, inferiorly by the mylohyoid muscle (m. mylohyoideus), and laterally by the genioglossus (m. genioglossus) and hyoglossus (m. hyoglossus) muscles.
- Cellular tissue of the inferior surface of the tongue — abundant loose connective tissue beneath the mucous membrane.
The cellular tissue of the floor of the oral cavity also communicates with the cellular space of the submandibular salivary gland bed along its excretory duct.
What are the boundaries of Pirogov's lingual triangle and what passes through it?
Pirogov's lingual triangle serves as a landmark for surgical access to the lingual artery and has the following boundaries:
- Superiorly: hypoglossal nerve (n. hypoglossus, XII pair).
- Anteriorly: posterior border of the mylohyoid muscle (m. mylohyoideus).
- Inferiorly and posteriorly: tendon of the posterior belly of the digastric muscle (m. digastricus).
- Floor: hyoglossus muscle (m. hyoglossus).
Within the triangle pass the lingual artery (a. lingualis), which lies deep beneath the floor muscle, and the lingual vein (v. lingualis).
Class and exam questions
Which muscles form the floor of the oral cavity?
The base of the floor of the oral cavity is formed by the mylohyoid muscle (m. mylohyoideus), spanned between the mandible and the hyoid bone.
Where do the ducts of the salivary glands open?
The submandibular duct and the major sublingual duct open at the sublingual caruncle (caruncula sublingualis). The minor ducts of the sublingual glands open on the sublingual folds.
Which nerve provides taste sensation to the anterior two-thirds of the tongue?
Taste sensitivity of this zone is provided by the chorda tympani—a branch of the facial nerve (VII pair).
How does the hyoglossus muscle (m. hyoglossus) separate blood vessels and nerves?
On the inner side of this muscle runs the lingual artery, and on the outer side—the lingual vein and the hypoglossal nerve (XII pair).
What else to study on this topic
- Topography of the lingual nerve in relation to the submandibular gland duct
- Extrinsic muscles of the tongue and their functions
- Branches of the lingual artery and their blood supply zones
- Structural features of the mucous membrane in various zones of the tongue
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