Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, we're going to be talking about the structure of the tongue. And to do so, we’re going to be looking at this image that you see now on the screen which is basically an image of the superior view of the tongue also known as the dorsum of the tongue.
And let’s start with the very first highlight that you now see, the first green highlight, which is the body of the tongue. The body of the tongue is bordered anteriorly by the tip also known as the apex and posteriorly by the structure here which is known as the root of the tongue. The body makes up the anterior 2/3 of the entire tongue and there is also this structure here, this depression, which is known as the median sulcus which runs along the middle of the body of the tongue vertically. The mucosa of the body of the tongue is covered in a lot of structures known as the lingual papillae, plural for papilla. Now, the list includes filiform papillae, the fungiform papillae, the vallate papillae, and also foliate papillae. Now, these structures, these papillae, contained taste buds with the exception of the filiform papillae.
We’re going to move on to another highlight here of a structure that I just mentioned before, this is known as the median sulcus. The median sulcus of the tongue is a groove that runs from the apex of the tongue to just in front of the beginning of the root of the tongue. This sulcus will be dividing the body of the tongue into a left and right side.
Next highlight which I also mentioned before, this is known as the apex of the tongue, a fancy word to just meaning or describing the anterior most portion of the tongue, or, in other words, the tip of your tongue.
The next structure that we’re going to be highlighting is known as, also one that I talked about, the root of the tongue, which is the posterior most portion of the tongue. This structure will be then anchoring the tongue to the mandible and the hyoid bone. The root makes up 1/3 of the tongue and contains the lingual tonsils and it is separated from the body of the tongue by a V-shaped terminal sulcus which you see a little bit here on this image, this is the terminal sulcus, which we also will be highlighting on the next slide. So, this is the terminal sulcus which is a V-shaped groove that separates 2 structures - the root and, also this one here that we talked about before, the body of the tongue. As you can see here, the vallate papillae, they run parallel to the terminal sulcus. So, these dots that you see here represented on this illustration.
The next area that we’re going to be highlighting here on this image, this is where we find the foliate papillae. They are located on the posterolateral end of the body of the tongue. They contain several taste buds.
Next, we’re going to be highlighting these dots that I just mentioned before, these are the vallate papillae. They are also known as circumvallate papillae and are located in the front of the foramen cecum which is this structure here, this little dot that you see, which is found near the root of the tongue. The vallate papillae, they run parallel to the terminal sulcus as I mentioned before and are covered by stratified squamous nonkeratinized epithelium. Something important that you should have on your notes is that these structures are innervated by the glossopharyngeal nerve which is a cranial nerve - to be more specific, it is the cranial nerve no. 9. As you can see here and as I mentioned the vallate papillae, they are innervated by the glossopharyngeal nerve unlike the rest of the body of the tongue that get its sensory innervation from the chorda tympani which is a branch of the facial nerve and also the lingual nerve.
The next structure which we also talked about before, this dot here represents the foramen cecum of the tongue. The foramen cecum is located at the midline just anterior to the terminal sulcus on the body of the tongue. Now, this structure is an embryological remnant of the thyroglossal duct and is formed during the descent of the thyroid gland during embryological development.
Next structures highlighted here, these are known as the lingual tonsils. Now, the lingual tonsils are comprised of lymphatic tissue and covered the root of the tongue as you can see. Now, this mucosa-associated lymphoid tissue also known as MALT is covered by stratified squamous epithelium. The lingual tonsils contain lingual follicles.
Next structures that we’re going to be highlighting here, also tonsils, this time known as the palatine tonsils. They are comprised of lymphatic tissue and are located between the palatoglossal and palatopharyngeal arches of the oral cavity. They contain tonsillar crypts and epithelial invaginations called the tonsillar pits.
On the next slide, I’m going to be highlighting the epiglottis as you can see here. This comprise of elastic cartilage. The epiglottis is covered with mucous membrane and is located behind the tongue as you can see clearly on this image. The epiglottis is attached to the larynx and acts as a flap covering the larynx during swallowing to prevent then food from entering the respiratory tract. The mucosa of the epiglottis also contains what’s known as taste buds.
The next highlight that you see here is known as the epiglottic vallecula which are depressions located between the median and lateral glossoepiglottic folds. And as you can see here in the image, they’re located just behind the root of the tongue.
Next structure that we’re going to be highlighting here is known as the median glossoepiglottic fold and the median glossoepiglottic fold is formed by the mucous membrane that is located along the median plane between the epiglottis and the base of the tongue. On the sides we’re going to be finding these folds here which are known as the lateral glossoepiglottic folds and, in the same way as the median glossoepiglottic folds, they are formed by mucous membrane. They are partially attached to the pharyngeal wall and are located between the base of the tongue and also the epiglottis.
Next on our list, we’re going to be highlighting these arches here which are known as the palatopharyngeal arches. Now, the palatopharyngeal arches are found on either side of the oral cavity near the root of the tongue at the opening of the oral cavity to then the pharynx. So, a bit of location here, you can see here this is the oral cavity and just behind, you’re going to be finding the next structure which is then the pharynx. Now, these arches are covered by mucous membrane and are formed by projections. Some muscles, the palatopharyngeal muscles, which will be extending between the palate and the pharyngeal wall as well and, here on this image, we only see the bottom part of these arches.