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Pharyngeal mucosa and related structures.
Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, we're going to be talking about the parapharyngeal mucosa. So, what we’re going to be doing is describing this image that you see now on the screen. This is basically the posterior view of the pharynx as you can see. Now, what we did was just cut open this tube which is known as the pharynx and expose the different structures of the mucosa. Notice here this lining which separates the mucous membrane of the pharynx as well as the muscles here. Notice a difference in texture. These are the different muscles of the pharynx. A bit more of location here to understand what’s going on here on this image. We’re looking at the posterior view as I mentioned. Also of the skull where you see here these two landmarks which are the mastoid processes. Notice here also the sternocleidomastoid muscles, a bit of the masseter muscles which are then attached to the lower jaw.
Now, the pharynx is a muscular column that is located posterior to the oral cavity and also the nasal cavity and larynx that runs between then the oral cavity and the esophagus below. And as I mentioned, the pharynx is lined by mucosa and the muscle fibers that make up the wall circularly around the outside and longitudinally on the inside. Now, the pharynx is also an important structure for production of voice. It’s also a passageway for both food and air.
Now, as a reminder, we’re going to be talking about the different pharyngeal mucosa or the structures of the pharyngeal mucosa and related structures – structures that we find related or associated to the pharyngeal mucosa.
Now, let’s start off with the very first point which is how we divide the pharynx. Now, it can be divided into 3 structures: The nasopharynx which you see here highlighted in green; now a bit more inferiorly, you’re going to find the oropharynx; and the laryngopharynx which you see here a bit even more inferiorly now highlighted in green.
Now, we’re going to talk about these in a little bit more detail starting off with the nasopharynx that you see here highlighted in green which is located on the posterior part of the nasal cavity behind the conchae as you can see here. It is the uppermost portion of the pharynx and structures found in this portion of the pharynx include the nasopharyngeal tonsils or also known as the adenoids, the pharyngeal bursa, and the pharyngeal opening of the auditory tube. The nasopharynx communicates with the nasal cavity via these structures here which are known as the nasal conchae and also the oral cavity via the pharyngeal isthmus.
A bit further down, we’re going to find this highlight here which is the oropharynx which is the portion of the pharynx that is located between the nasopharynx and the laryngopharynx - remember the first images that we saw – just behind the oral cavity which you see a bit of the oral cavity here with the root of the tongue. Now, the oropharynx is going to extend from the soft palate as you can see here and the uvula in particular, to the level of the hyoid bone. In this portion of the pharynx, we find the vallecula epiglottica which is a fossa located between the lateral and median glossoepiglottic folds and the epiglottis. The mucosa of the oropharynx is made of a type of tissue which is known as nonkeratinized stratified squamous epithelium, and in this region, we also find the palatine tonsils somewhat visible from this aspect, as you can see here. And these are located between the palatoglossal arch and palatopharyngeal arch anteriorly.
We’re going to go a bit further down to highlight the structure that we already mentioned, the laryngopharynx. And this caudal most portion of the pharynx is located behind the larynx and extends from the region of the oropharynx to here, the esophagus. Now, structures found in the laryngopharyngeal portion of the pharynx include the piriform recess which you can see here on both sides of the laryngopharynx, and also the pharyngeal glands. The laryngopharynx is lined up with stratified squamous epithelium.
We’re moving onto the next structures that you see here highlighted in green which are known as the choana individually or as singular, or choanae. They’re also known as the posterior nasal aperture. As you see here from their location, they’re a part of one of the structures that we talked about before, the nasopharynx. Now, through these openings located on the posterior aspect of the nasal cavity, the nasopharynx communicates then with the nasal cavity.
Moving onto the next structures that you see here highlighted in green, which singularly, they’re known as the middle nasal concha; as plural as both, we named them the middle nasal conchae. Now, the middle nasal conchae is one of the three turbinates found in the nasal cavity. It is located between the superior nasal concha and the inferior nasal concha. The middle nasal concha will be draining several structures including the middle nasal meatus, the anterior and middle ethmoidal sinuses, the frontal sinus, and the maxillary sinus. On this image, we can see the posterior part of the middle nasal conchae here through the choanae, as you can see the previous structures that we just highlighted, these openings. Now, below we will be highlighting these structures which are known as the inferior nasal conchae. And the inferior nasal concha is the largest of the 3 nasal conchae seen from this posterior aspect through the choanae. The inferior nasal conchae drains the inferior meatus and the nasolacrimal duct.
Next structures that we’re going to be highlighting here, these folds which are known as the torus tubarius. The torus tubarius is an elevation of the Eustachian or auditory tube seen from the nasal cavity. It is covered by mucosa and can also be seen here from the posterior aspect.
Next on our list, we’re going to be highlighting these folds here which have a similar name but this time, we’re calling them the torus levatorius. The torus levatorius seen here just below the torus tubarius is an elevation that is produced by a muscle, the levator veli palatini muscle. Now, this muscle is a muscle of the soft palate which is, as the name states, will be elevating the soft palate during swallowing and also aids in stopping food from entering the nasopharynx.
Next structures that we’re going to be highlighting, next structure here, which is known as the nasal septum. The nasal septum separates the two sides of the nasal cavity and is comprised of bone as well as cartilage. From this aspect we see the posterior part of the nasal septum.
Next structures that you see here highlighted are known as the pharyngeal recesses and the pharyngeal recesses are located behind the Eustachian tube on the lateral aspect of the nasopharynx as you can see here on this image.
The next structure that we’re going to be highlighting here, one on each side, these are known as the salpingopharyngeal folds. These are ridges seen at the level of the nasopharynx formed by a muscle as well, the salpingopharyngeus muscle.
The next structures that we’re going to be talking about, or next structure which we talked about before is the soft palate. Now, the soft palate has no bony skeleton which compared to the hard palate that is formed by bones as well. Now, the soft palate is located posterior to the hard palate and it has a muscular plate that is comprised of the tensor veli palatini muscle. Still on the same highlight but I want to differentiate here, this structure which is known as the famous uvula, also known as the palatine uvula. This is a conical projection of the posterior free edge of the soft palate that hangs down into the oropharynx.
Moving on, we’re going to highlight now this arch here which is known as the palatopharyngeal arch or arches. There are 2 folds of mucous membrane located at the level of the oral pharynx that overlie the palatopharyngeal muscle. One of the functions of the palatopharyngeal muscle is to depress the palate and this muscle is innervated by the vagus nerve, also known as the 10th cranial nerve. If you remember, when we talked about the oropharynx, this structure here is the root of the tongue. Now, the root of the tongue is the posterior part of the tongue that anchors this structure to the mandible and the hyoid bone.
Again, be seen here in the oropharyngeal portion of the pharynx and structures found on the root of the tongue include then the terminal sulcus, the vallate papillae that are located in the front of the terminal sulcus and also contain taste buds; the foramen caecum of the tongue which is an embryological remnant of the thyroglossal duct, and the lingual tonsils.
We’re moving onto the structures here that I also talked about before, these are the palatine tonsils. The palatine tonsils are comprised of lymphoid tissue and are an example of mucosa-associated lymphoid tissue, also known as MALT. Now, they are involved in humoral and cellular immunity and strategically situated between the palatoglossal and the palatopharyngeal arches which are the openings of the gastrointestinal and respiratory tracts in the oral cavity.
The next structure that we’re going to be highlighting is the well-known structure, the epiglottis. Now, the epiglottis is covered by covered by mucous membrane and is made up of elastic cartilage. The epiglottis closes during swallowing to close off the larynx from the food bolus so the food that you are taking from your mouth to your stomach but it is, otherwise, open when you’re breathing.
There is another structure here in the larynx worth highlighting. It’s known the laryngeal inlet. Now, the laryngeal inlet is the opening found on the laryngopharyngeal part of the pharynx that opens from the pharynx to the larynx. Now, this is the connection between the pharynx and the larynx as you would expect and, during swallowing, the laryngeal inlet is closed by the epiglottis to prevent food and liquid from entering the respiratory tract. So, you want food to go the esophagus and then stomach and not to the lungs through the larynx.
The next structures that you see here highlighted in green are known as the aryepiglottic folds. They are located at the opening of the larynx. They are mucosal folds overlying the aryepiglottic muscle. The aryepiglottic folds are bounded by the arytenoid cartilages at the apex and the epiglottis. These folds aid in phonation.
The next structures seen here highlighted, the next structure is known as the interarytenoid notch. And, as the name implies, this is a depression or indentation found between the 2 apices of the arytenoid cartilages. As you can see here and this is why we are also including in this tutorial, the interarytenoid notch is covered by mucosa.
Next on our list, we’re going to highlight this structure here, which is known as the pharyngeal tonsil. They’re also known as the adenoids and are comprised of lymphatic tissue that are located in the nasopharyngeal portion of the pharynx.
A bit further down, we’re going to continue on to these structures here highlighted in green which are known as the cuneiform tubercles. The cuneiform tubercle is a mucosa-covered prominence formed by the underlying cuneiform cartilage and is located on the posterior part of the aryepiglottic folds. There’s also another pair of tubercles here which are known as the corniculate tubercles and the corniculate tubercles are eminences found by the underlying corniculate cartilage and, in the same way as the cuneiform tubercles, they are also covered by mucosa of the pharynx. Now, these tubercles are smaller than the cuneiform tubercles and are located medially on the posterior aspect of the aryepiglottic fold.
Next structures on our list as you can see here, this is the piriform fossa. The piriform fossa is found in the laryngopharynx as we talked about on the first slides. They’re located between the aryepiglottic folds and the thyroid cartilage on either side of the laryngeal inlet. Keep in mind that we can also call it piriform recess. The mucosa of the piriform recess houses a branch of the superior laryngeal nerve which is the internal laryngeal branch of the superior laryngeal nerve, you can see these elevations here on this green highlight, which we will be highlighting next because we can also call these the folds of the superior laryngeal nerve. And as I mentioned before, these are found on the piriform recess or fossa. Now, it is formed by then the internal laryngeal branch of the superior laryngeal nerve, keep that in mind, which is a branch of the superior laryngeal nerve that underlies the mucosa of the piriform recess.
And the last part going all the way down, you find this highlight here which is the beginning of the esophagus. Now, the esophagus is a fibromuscular tube that extends from the pharynx to the cardiac portion of the stomach. The lumen of the esophagus is lined with stratified squamous epithelium. The food bolus is transmitted through the esophagus via the peristaltic action of the smooth muscle of the esophagus. So the food is able to go from the oral cavity to the pharynx then to the esophagus and then arriving at the stomach to then follow a longer path until it is expelled in a different shape and form.