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Functions, Embryonic Development, and Neurovascular Supply of the Tongue

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The human tongue is responsible for varied functions. Read the article to know the functions, embryonic development, and the musculature of this essential organ.

Medically reviewed by

Dr. Chithranjali Ravichandran

Published At May 7, 2022
Reviewed AtDecember 20, 2022

Introduction:

The tongue is an essential muscular organ found as a unique entity in all the vertebrates in the oral cavity. It is mainly attached via muscles to the hyoid bone, mandible, styloid process, palate, pharynx, etc.

What Are the Functions of the Tongue?

Taste Perception:

The tongue has several functions, the main of which we know is the essence of identifying taste. This is because of chemicals that interact with the taste buds in the tongue that are known as "tastants." The taste buds are found within the various papillae in the tongue that interact with gustatory cell receptors resulting in the feeling or perception of a taste sensation. There are also five broad categories of taste receptors that are either sweet, salty, sour, bitter, and umami found within the vallate (or circumvallate), fungiform, filiform, and foliate papillae.

Speech:

Speech is produced mainly by the manipulative or guided movement of the tongue in the mouth. The importance of intrinsic muscles of the tongue discussed below in this article, later on, are mainly involved in shaping the tongue for speech.

Food Ingestion:

The tongue helps or aids in the ingestion of food through the mouth by the movement against the hard palate and out to the sides of the oral cavity, i.e., the teeth and oral mucosa, to enable mastication. It enables the formation of the food bolus in the preparatory phase of swallowing.

How Is Tongue Developed?

The tongue development begins in the embryo around four weeks' gestation. Initially, there are two lateral lingual swellings that are present called the tuberculum impar that arises from the first pharyngeal arch and a second swelling called the copula or hypobranchial eminence that develops from the mesoderm of the second, third, and fourth pharyngeal arches.

The lateral lingual swellings eventually not only increase in size but also merge into each other, overlapping the tuberculum impar itself. This is the merger that forms the anterior two-thirds of the tongue. The mucosa overlying the anterior 2/3 part of the tongue originates from the first arch, and its sensory innervation is supplied by the mandibular branch of the trigeminal nerve (CN V3). Also, the second, third, and fourth remnants or pharyngeal arch portions developed as copula further get formed into the posterior one-third of the tongue. The mucosa overlying this posterior part of the tongue derives its sensory innervation from the glossopharyngeal nerve (CN IX).

The epiglottis region of the tongue further develops from the third median swelling, which arises from the fourth posterior pharyngeal arch. The innervation of this region is supplied by the superior laryngeal nerve, which is derived again from the fourth pharyngeal arch.

The muscles of the tongue also predominantly are derived to an extent from the myoblasts that originate in occipital somites, and these muscles of our tongue are innervated by the hypoglossal nerve (CN XII).

Which Are the Muscles of the Tongue?

A septum divides the tongue into right and left halves. Each half contains four intrinsic and four extrinsic muscles.

The intrinsic muscles are found in the upper part of the tongue and are attached to the submucosal fibrous layer, and they are superior longitudinal and lie beneath the mucous membrane. It curls the tip upward and rolls it posteriorly. Inferior longitudinal muscle is a narrow band lying between the genioglossus and the hyoglossus, and they curl the tip close to the inferior surface of the tongue, and the transverse muscle extends from the medial septum to the margin, they narrow the tongue. Vertical muscle is located at the borders of the anterior part of the tongue, and it flattens the dorsum of the tongue inferiorly.

Extrinsic muscles are:

  • Genioglossus connects the tongue to the mandible, it originates from superior mental spines, inserts into the mucous membrane of the tongue, protrudes the tongue, depresses the central part of the tongue, and increases the volume of mouth sucking.

  • Hyoglossus arises from a greater horn and body of the hyoid bone, inserts inside of the tongue, and it depresses the side of the tongue, assisting genioglossus in enlarging the oral cavity.

  • Styloglossus originates from the lower part of the styloid process and the upper part of the stylohyoid ligament, inserts inside the tongue, elevates, and retracts the tongue.

  • Palatoglossus originates from the soft palate, and it inserts into the lateral margin of the tongue. It elevates the back of the tongue and depresses the soft palate.

How Is the Nerve Supply to the Tongue?

A somatic-motor supply is by the hypoglossal nerve that supplies all extrinsic and intrinsic muscles of the tongue except palatoglossus, and the cranial part (via the vagus nerve) supplies the palatoglossus tongue sensory nerve. Secretomotor to lingual glands supply is by preganglionic fibers that arise in the superior salivatory nucleus and pass to the submandibular ganglion via the facial nerve, chorda apani, and lingual nerve and postganglionic fibers are conveyed via a lingual nerve. Vasomotor is derived from the sympathetic plexus around the lingual artery. Fibers are derived from superior cervical ganglion. Lingual nerves supply general sensation from the anterior 2/3rd of the tongue. Chorda tympani supply taste sensations from anterior 2/3rd except vallate papillae. The glossopharyngeal nerve conveys all general sensations from the posterior 1/3rd of the tongue, and it carries taste sensations from vallate papillae. Internal laryngeal branch of the superior laryngeal nerve from the vagus conveys taste sensation from the posterior most part of the tongue.

How Is the Arterial and Venous Supply to the Tongue?

The lingual artery, a branch of the external carotid artery, is the chief artery of the tongue, ascending palatine artery, branch of the facial artery, and tonsillar artery, branch of the facial artery.

Venous Drainage:

Superficial veins drain the tip and under the surface of the tongue and pass along with the hypoglossal nerve over the hyoglossus muscle and deep vein of the tongue. These veins unite at the posterior border of the hyoglossus to form the lingual vein, which terminates into the internal jugular vein.

How Is the Lymphatic Drainage to the Tongue?

The drainage zones of the tongue can be grouped into three. The tip and inferior surface of the tongue drains into submental lymph nodes. Anterior 2/3rd of the dorsum of the tongue, i.e., each half drains into ipsilateral submandibular lymph nodes and then to lower deep cervical lymph nodes, few lymphatics from the central region, within an inch of the midline, drain bilaterally into submandibular lymph nodes. Posterior 1/3rd of the dorsum of the tongue drains bilaterally into the upper deep cervical lymph nodes, including the jugulo-digastric.

Conclusion:

The rich innervation and neuromuscular supply from the tongue, apart from its multivariate functionality, makes the tongue an extremely important and crucial organ of sense perception, speech, and taste.

Frequently Asked Questions

1.

What Is the Embryology Behind Tongue Development?

The embryology of the development of the tongue involves the formation of three types of tissue: endoderm, ectoderm, and mesoderm. The tongue develops from the first and second pharyngeal arches, which give rise to the tongue's muscles, nerves, and blood vessels. The endoderm forms the lingual papillae and taste buds, while the ectoderm forms the epithelial covering of the tongue. The mesoderm gives rise to the intrinsic and extrinsic muscles of the tongue.

2.

What Is the Tongue's Nerve Supply Like?

The nerve supply of the tongue is complex and involves several cranial nerves (CN). The lingual nerve, a branch of the mandibular division of the trigeminal nerve (CN V3), provides sensory innervation to the anterior two-thirds of the tongue. In contrast, the glossopharyngeal nerve (CN IX) provides sensory innervation to the posterior one-third of the tongue. The hypoglossal nerve (CN XII) provides motor innervation to the intrinsic and extrinsic muscles of the tongue.

3.

Name the Four Cranial Nerves That Innervate the Tongue and Their Uses?

The four cranial nerves that innervate the tongue and their functions are: 
- Trigeminal nerve (CN V): Provides sensory innervation to the anterior two-thirds of the tongue. 
- Facial nerve (CN VII): Provides taste sensation to the anterior two-thirds of the tongue.
- Glossopharyngeal nerve (CN IX): Provides sensory innervation to the posterior one-third of the tongue and taste sensation to the posterior one-third of the tongue. 
- Hypoglossal nerve (CN XII): Provides motor innervation to the intrinsic and extrinsic muscles of the tongue.

4.

Which Nerve Affects the Tongue?

The nerve that affects the tongue is the hypoglossal nerve (CN XII). It innervates the intrinsic and extrinsic muscles of the tongue and is responsible for the movement and coordination of the tongue during speech and swallowing.

5.

Which Area of the Brain Controls the Tongue?

The part of the brain that is responsible for the tongue is the motor cortex, specifically the area known as the primary motor cortex (M1). The motor cortex controls the voluntary movements of the tongue. It receives input from other brain areas, such as the sensory cortex, which receives sensory information from the tongue.

6.

Is the Tongue a Nerve or a Muscle?

The tongue is primarily a muscle, with various muscles working together to facilitate movements and functions. However, the tongue also contains nerve tissue responsible for the tongue's sensory and motor functions.

7.

Name the Tongue Muscle?

The name of the tongue muscle is the lingual muscle, divided into intrinsic and extrinsic muscles. The intrinsic muscles are responsible for fine tongue movements, such as shaping during speech and swallowing. In contrast, the extrinsic muscles allow for broader movements, such as protruding or retracting the tongue.

8.

Name the Nerve Connecting the Tongue to the Brain?

The nerve that leads from the tongue to the brain is the hypoglossal nerve (CN XII). This nerve originates in the brainstem and provides motor innervation to the tongue muscles, allowing movement and coordination.

9.

How is the Tongue and the Brain Linked?

The connection between the tongue and brain is complex, with multiple nerves and brain regions involved in the tongue's functions. The tongue sends sensory information to the brain via various nerves, including the lingual nerve (a branch of the trigeminal nerve), glossopharyngeal nerve (CN IX), and vagus nerve (CN X). This sensory information is processed in various brain regions, including the primary sensory cortex and gustatory cortex, allowing us to perceive taste and texture sensations. The brain also sends motor signals to the tongue via the hypoglossal nerve (CN XII), allowing for voluntary movements and tongue coordination.

10.

State the Number of Nerves In the Tongue?

There are several nerve in the tongue including the lingual nerve, hypoglossal nerve, glossopharyngeal nerve, and vagus nerve. These nerves are responsible for various functions, such as providing sensory and motor innervation to the tongue, allowing for taste perception, and coordinating the movements of the tongue during speech and swallowing.

11.

Where Is the Tongue's Root Situated?

The root of the tongue is the part of the tongue located at the back of the mouth and connects to the hyoid bone. It is divided into the posterior one-third of the tongue and is innervated by the glossopharyngeal nerve (CN IX).

12.

Name the Strongest Tongue Muscle?

The strongest muscle of the tongue is the genioglossus muscle, an extrinsic muscle that originates from the mandible and attaches to the tongue. It is responsible for protruding and retracting the tongue and is essential for speech and swallowing.

13.

Which Cranial Nerve Is Responsible for Numbness in the Tongue?

Tongue numbness can be caused by several factors, including injury or compression of the lingual nerve (a branch of the mandibular division of the trigeminal nerve, CN V3) or the glossopharyngeal nerve (CN IX). In some cases, tongue numbness may also be a symptom of a more severe condition, such as a stroke or tumor.

14.

What Is the Purpose of the Division of Tongue?

The tongue is divided into two main parts: the anterior two-thirds and the posterior one-third. The anterior two-thirds of the tongue is innervated by the lingual nerve (a branch of the mandibular division of the trigeminal nerve, CN V3). In contrast, the posterior one-third is innervated by the glossopharyngeal nerve (CN IX). This division is essential for the sensory and motor functions of the tongue and taste perception.

15.

What Does the Structure of the Tongue Entail?

The tongue is a muscular organ that is covered with a mucous membrane. It is divided into two main parts, as mentioned above, and contains various types of papillae, including filiform, fungiform, and circumvallate papillae. The tongue also contains taste buds responsible for taste perception and various glands that secrete saliva. The structure of the tongue allows for its various functions, such as taste perception, speech, and swallowing.
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Dr. Achanta Krishna Swaroop
Dr. Achanta Krishna Swaroop

Dentistry

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