Anatomy of the tongue

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Introduction0:00–0:53

The tongue is part of what makes these videos possible. Without it, we couldn’t speak!
It is also what allows us to enjoy the taste of our favourite foods, and helps us get the occasional pesky bit of food out from between our teeth.
Now, the tongue is essentially a mass of muscles covered by a mucous membrane, which can contract and relax quickly, allowing the tongue to assume many shapes and positions.
This is what makes the tongue ideal for speaking by aiding sound formation. The tongue is also involved in taste via taste receptors; it pushes food into the oropharynx during swallowing; it helps with mastication by moving food closer to our teeth; and in oral cleansing.Looking at things in more detail, the tongue takes up much more space in the mouth than you might realize.

Structure0:53–1:43

It consists of a root, a body and an apex, with the last two being highly mobile. The root of the tongue is posterior and slightly vertical, forming the posterior one third of the tongue.
It extends from the hyoid, epiglottis, and soft palate, to the mandible. The body forms the anterior ⅔ of the tongue, and the apex of the tongue is the most anterior end of the body.
The entirety of the tongue rests on the mouth’s floor both in the oral cavity and into the oropharynx, with the apex pressing against the lower incisors.
The tongue also has two surfaces, supero-posterior and inferior, which are separated by the margin of the tongue. The supero-posterior surface is the larger of the two and it literally represents the “top” or dorsum of the tongue.

Supero-posterior surface1:43–5:10

The inferior surface or “underside” rests against the floor of the mouth. The dorsum of the tongue is characterized by a V-shaped groove called the terminal sulcus.
The sulcus divides the top of the tongue transversely into a presulcal anterior part in the oral cavity and a postsulcal posterior part situated in the oropharynx.
The V’s tip points posteriorly to something called the foramen cecum, which represents the remnant of part of the embryonic thyroglossal duct, from which the thyroid gland developed.
The dorsum also presents a central groove called the median lingual sulcus, which separates the anterior part of the tongue into a right and left division.
This area is sprinkled with numerous different types of lingual papillae. There are four main types of lingual papillae including vallate, foliate, filiform and fungiform papillae which give the tongue its rough texture.
All of these papillae contain taste-buds with the exception of the filiform papillae. First off, there are large and flat vallate papillae, which are arranged in a V-shaped row directly anterior to the terminal sulcus.
The papillae are surrounded by circular trenches, whose walls contain the actual taste buds. Second, foliate papillae are poorly developed lateral folds of lingual mucosa which are more developed in animals than humans.
They are located posteriorly, lateral to the terminal sulcus. Next, filiform papillae are scaly, conical projections covering most of the anterior ⅔ of the tongue.
Filiform papillae do not contain taste buds but they contain touch-sensitive nerve endings and they help with scraping movements that allow soft foods, like ice cream, to enter your mouth.
Fun fact: in cats, these papillae are much more developed, which helps them with grooming! Lastly, fungiform papillae are mushroom-shaped structures located amongst the filiform papillae, especially at the apex and margins of the tongue.
The mucosa of the posterior part of the tongue, situated posterior to the terminal sulcus is thick and contributes to the anterior wall of the oropharynx.
It presents no lingual papillae, but it’s scattered with lymphoid nodules, which give it a cobblestone appearance. These nodes are collectively known as the lingual tonsils and they are involved in the immune response to oral pathogens.

Inferior surface5:10–6:08

Now, the inferior surface of the tongue, or its “underside”, is the smooth surface that rests against the mouth’s floor.
It is smooth because it is covered in a thin, transparent mucous membrane which is connected to the floor of the mouth by a fold of tissue called the frenulum.
The frenulum allows free movement to the anterior part of the tongue, while also helping to anchor the tongue within the mouth.
On each side of the frenulum you can actually see a deep lingual vein and a sublingual caruncle, which is a small swelling of tissue.
The sublingual caruncles on each side contain the openings of the submandibular ducts, through which the submandibular salivary glands empty their contents into the oral cavity.
Try looking for these structures on yourself, by looking in a mirror and lifting up your tongue!Next, let’s talk about the muscles that make up our tongue.

Muscles6:08–9:35

These can be divided into extrinsic and intrinsic muscles, which act independently or together to alter the position and shape of the tongue.
The four intrinsic and four extrinsic muscles in each half of the tongue are separated by the median lingual septum. In general, the extrinsic muscles alter the position of the tongue while the intrinsic muscles alter its shape.
Let’s begin with the extrinsic muscles of the tongue which include the genioglossus, hyoglossus, styloglossus, and palatoglossus.
Their role is mainly in moving the tongue but they can help alter its shape as well. First, the genioglossus is an anterior, fan-shaped muscle that accounts for most of the tongue muscle.
It originates on the mental spine of the mandible and inserts on the dorsum of the tongue and the body of the hyoid bone.
Its main actions include tongue depression, protrusion, and contralateral deviation. Bilaterally the genioglossus muscles create a longitudinal furrow that helps during swallowing.
The hyoglossus sits posterior to the genioglossus and it originates on the body and greater horn of the hyoid bone.It then goes on to insert on the infero-lateral part of the tongue.
Its main role is in tongue depression and retrusion. Next is the styloglossus, and as its name suggests, it originates on the distal styloid process and stylohyoid ligament.
It then inserts on the posterior sides of the tongue between the fibers of the hyoglossus muscle. It helps retrude and curl or elevate the sides of the tongue which works with genioglossus during swallowing.
And finally, the palatoglossus originates on the palatine aponeurosis of the soft palate, and inserts on the posterolateral aspect of the tongue blending with fibers from the intrinsic tongue muscles.
Its role is in elevating the posterior tongue and depressing the soft palate. Now, let’s talk about the intrinsic muscles of the tongue which include the superior and inferior longitudinal, transverse, and vertical muscles.
They have their attachments entirely within the tongue and are not attached to any bone. First, the superior longitudinal muscle is involved in shortening and curling the apex and sides of the tongue upward while the inferior longitudinal muscle shortens and curls the apex and sides back downward.
Next, the transverse muscle’s main role is in narrowing and elongation of the tongue, while the vertical muscle has the opposite effect to its transverse brother as it flattens and broadens the tongue.
These two muscles work together to help protrude the tongue as well.Time for a quick break. Can you recall the four extrinsic and the four intrinsic muscles of the tongue?Now let’s talk about innervation!

Quiz9:35–9:53

Innervation9:53–13:00

Ok, so, all muscles of the tongue, except the palatoglossus which is supplied by the pharyngeal plexus, receive motor innervation from the twelfth cranial nerve, called the hypoglossal nerve.
After exiting the hypoglossal canal, the hypoglossal nerve heads downwards towards the inferior angle of the mandible, crossing the internal and external carotid arteries laterally and it sits medial to the posterior belly of the digastric muscle.
It then reaches the submandibular triangle, where it lies medial to the submandibular gland and courses anteriorly on the lateral aspect of the hyoglossus muscle and deep to the mylohyoid muscle.
Finally it reaches the tongue, where it provides motor branches to the intrinsic and extrinsic muscle of the tongue. When it comes to sensory innervation, the mucosa of the anterior two thirds of the tongue is supplied by different nerves.
For example, general sensation is supplied by the lingual nerve, a branch of the mandibular division of the trigeminal nerve.
The lingual nerve originates in the infratemporal fossa, and descends anteriorly on the medial aspect of the mandible. The lingual nerve then passes from lateral to medial looping under the submandibular duct where it finally enters the lateral margin of the tongue to supply general sensation to its anterior two-thirds.Special sensory or taste sensation of the anterior ⅔ of the tongue is relayed to the brain via the chorda tympani nerve, a branch of the seventh cranial nerve - the facial nerve.
The chorda tympani also exits the skull into the infratemporal fossa where it merges to hitch a ride with the lingual nerve to get to the anterior two thirds of the tongue, which allows the special afferent fibers to relay special sensation back to the brain, making sure we all have impeccable taste.
Now, you may be thinking, but what about the posterior ⅓ of the tongue? Well, general and special taste sensation to the mucosa of the posterior third of the tongue and the vallate papillae are relayed to the brain via the ninth cranial nerve, the glossopharyngeal nerve.
This nerve enters the pharynx between the superior and middle pharyngeal constrictor muscles, where it divides into branches to the palatine tonsils, the posterior wall of the pharynx, and the tongue.
By contrast, a small area of the tongue just anterior to the epiglottis is supplied mainly for general, but also some special sensation via the internal laryngeal nerve, a branch of the vagus nerve.Finally, it is also important to note that we have five basic taste sensations: sweet, salty, sour, bitter, and umami, with the tongue having areas that are more sensitive to some of these sensations than others.

Basic taste sensations13:00–13:52

Although all areas of the tongue are capable of detecting each of these 5 tastes, different areas detect these tastes at different intensities.
For example, sweetness is mainly detected at the apex, saltiness at the lateral margins, sourness more posteriorly at the lateral margins, bitter at the posterior aspect around the terminal sulcus and lastly, umami at the central part of the tongue.Time for a quick quiz!

Quiz13:52–14:15

Can you recall the general and special sensory innervation of the anterior 2/3s of the tongue? What about the general sensory and special sensory innervation of the posterior 1/3 of the tongue?Now, let’s talk about the blood supply of the tongue, which is mainly provided by the lingual arteries.

Vascular supply14:15–14:43

The lingual arteries are anterior branches of the external carotid arteries, arising on the middle pharyngeal constrictor from where they move towards the hyoid bone.
Upon entering the tongue, the lingual arteries pass deep to the hyoglossus muscles and branch to supply the entire tongue.

Venous and lymphatic drainage14:43–15:03

Venous blood is drained via the lingual veins and their tributaries. Finally, lymph from the tongue drains to the superior and inferior deep cervical lymph nodes, as well as the submandibular and submental lymph nodes.

Review15:03–17:06

Alright, as a quick recap! The tongue has three main parts: a root, a body and an apex; and two surfaces: the inferior surface and the supero-posterior surface, also known as the dorsum of the tongue.
The 4 types of lingual papillae found on the dorsum of the tongue include the vallate, foliate filiform and fungiform papillae.
The mucosa of the posterior 1/3 of the tongue is scattered with lymphoid nodules, together known as the lingual tonsils.
The four extrinsic muscles of the tongue are the genioglossus, hyoglossus, styloglossus, and palatoglossus. Their role is mainly in moving the tongue but they can help alter its shape as well.
The intrinsic muscles of the tongue include the superior and inferior longitudinal, transverse, and vertical muscles, and they mainly help control the shape of the tongue.
All muscles of the tongue, except the palatoglossus, receive motor innervation from the hypoglossal nerve. General sensation to the anterior ⅔ of the tongue is supplied by the lingual nerve, while special taste sensation is supplied by the chorda tympani nerve.
The posterior ⅓ of the tongue gets general and special taste sensation mainly from the glossopharyngeal nerve. Blood supply to the tongue is mostly through the lingual arteries, while venous blood is drained via the lingual veins.
Lymph from the tongue drains to the superior and inferior deep cervical lymph nodes, as well as the submandibular and