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Overview of the oral cavity

The oral cavity is the first part of the digestive system.

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Transcript

Hello everyone! It's Megan from Kenhub here, and welcome to our tutorial where we're going to do an overview of the oral cavity outlining and locating the major structures. The image you can now see in front of you is going to be the main focus throughout this tutorial showing an anterior view of the oral cavity. The oral cavity is the beginning of the digestive tract but is also involved in tasting and the modification of signs to facilitate communication. So let's have a look at how the different structures of the oral cavity work together to accomplish these different tasks.

Before we do so, we need to know that the mouth can be broadly divided into two parts – the oral vestibule and the oral cavity proper. This division is marked by the gums and teeth dividing the mouth into two distinct and separate regions. First, we'll talk about the oral vestibule. The oral vestibule can be defined as the mouth area bordered anteriorly and laterally by the lips and cheeks and posteriorly and medially by the teeth and gums. So, basically, the oral vestibule is the space external to the teeth and gums. Although the oral vestibule is part of the mouth, it's worth noting that it's not strictly considered to be part of the oral cavity.

We're now going to talk about structures that are part of the oral vestibule starting with the labial frenula. The labial frenula are located in the median plane and attached the center of the lips to the gum between the upper and lower two front teeth. In the illustration on the right, we can see the inferior labial frenulum highlighted in green and in the next image, we can see the superior labial frenulum. The role of the superior and inferior labial frenula is to support and restrict the motion of the lips.

Now that we've covered the oral vestibule, it's time for us to move on to our next topic which is the oral cavity proper. As I mentioned earlier, the oral cavity proper is the second region of the mouth. This region is limited anteriorly and laterally by the teeth and gums and superiorly by the hard and soft palates. The posterior border of the oral cavity proper is marked by the tonsils where the soft palate curves slightly downwards. Posteriorly, the oral cavity proper continues into the larynx and pharynx.

The first structure of the oral cavity we're going to talk about is as you would probably guess – the tongue. We all know that the tongue is a structure that can be found in the inferior space of the oral cavity proper. The tongue can be divided into different parts but on this image we can see the body highlighted in green. The body of the tongue is for responsible for many of the sound modification and communication tasks performed by the mouth. This highly muscularized and vascularized structure also plays a central part in digestion aiding the mechanical preparation of food for swallowing.

The next structures of the oral cavity that we'll talk about form what is known as the roof of the mouth. These structures are known collectively as the palate which is the superior border of the oral cavity proper and what your tongue presses up against. It can be further divided into the hard palate which we can see here and the soft palate which we can see here. The hard palate spans the anterior arch formed by the upper teeth. It consists of the two palatine shelves of the maxilla which are fused down the midline as well as the fused palatine bones posteriorly. It's covered by oral mucosa on its inferior aspect which faces the oral cavity. The hard palate is very important for both feeding and communication so much so that mammals with a defective hard palate may die shortly after birth due to an inability to suckle. The interaction between the tongue and the hard palate is also essential for the generation of certain sounds.

Posterior to the hard palate is the soft palate. This structure can be distinguished from the hard palate due to the fact that it doesn't contain any bone. Rather, it's a movable structure consisting of muscle fibers sheathed in mucous membrane. It's also distinguishable by its color as the soft palate is a darker red with a yellowish tint. The soft palate is responsible for closing off the nasal passages during the act of swallowing and also for closing the airway.

One of the well-known projections that we find in the back of our mouth is known as the uvula. This conic projection which is also referred to as the palatine uvula can be considered to be an extension of the posterior region of the soft palate. Note that in this image here, we see the lateral view of the oral cavity, a sagittal cut where we see the uvula from the side. You can clearly see here that the uvula hangs above the throat and is believed to be involved in numerous processes such as guiding the swallowing of food and water as well as providing saliva for digestion and assisting in communication. In the next illustration, we can see the uvula from an anterior perspective.

Further towards the back of the mouth, we see this structure highlighted in green – the isthmus of fauces. This is a cavity bound anteriorly by the palatoglossal arches, posteriorly by the palatopharyngeal arches and superiorly by the soft palate. You'll notice that between the palatoglossal arches and the palatopharyngeal arches, we find the palatine tonsils which we'll see a bit more clearly later on in this tutorial. When these two arches move closer together due to the contractions of the palatoglossal muscles, the isthmus will be constricted and this is very important for swallowing.

Now let's talk about the arches that I mentioned previously. In the posterior region of the oral cavity, we're going to find the prominent folds that we can see highlighted in these two images. Anteriorly, we have the palatoglossal arches which we can see here and posteriorly we have the palatopharyngeal arches which we can see here. It's easy to remember the distinction between these two structures just by looking at their names. Both start with the "palato-" prefix which means that they're related to the palate. "Glossal" from the palatoglossal arch indicates its relationship to the tongue whereas "pharyngeal" in palatopharyngeal arch indicates a relationship to the pharynx.

So let's take a closer look at the palatoglossal arches. The palatoglossal arches run downwards and laterally from the soft palate to the sides of the tongue. These arches contain the palatoglossal muscle which is covered by a mucous membrane.

Now we'll take a closer look at the palatopharyngeal arches which lie posterior to the palatoglossal arches. They project from the soft palate to merge with the lateral walls of the pharynx. Like the palatoglossal arches. The palatopharyngeal arches consist of the palatopharyngeus muscle covered by a mucous membrane.

The next structures found in the isthmus of fauces are the palatine tonsils commonly referred to as simply the tonsils. The palatine tonsils are lymphoid tissues and they're bordered anteriorly by the palatoglossal arches and posteriorly by the palatopharyngeal arches. These are the tonsils that are commonly removed surgically because of repeated tonsillitis, airway obstruction or sleep apnea. They form an important part of our immune system and due to their location at the gateway of the respiratory and digestive tracts, they often act as a first line of defense against pathogens.

The last structure seen in this image of the oral cavity and worth briefly mentioning is the posterior wall of the pharynx. The pharynx then extends downwards into the larynx to inhale and exhale air or into the esophagus for eating and drinking.

Now that we have a solid understanding of the anatomy of the oral cavity, let's go over some clinical notes relating to this area. There are diverse pathologies affecting the oral cavity either congenital or due to infection or inflammation or even malignancies. A common congenital birth defect of this region is cleft palate which occurs due to a lack of fusion between the palatine shelves during the facial development of the fetus. This produces a hole which opens into the nasal cavity causing problems with speech, feeding and hearing. Cleft palate can be successfully treated with surgery which is performed before the baby is eighteen months old.

An example of an acquired pathology of the oral cavity is a candida infection, a fungal yeast infection that affects the mouth due to poor hygiene or immunosuppression. Candida infections are the most common type of yeast infection which can fortunately be treated with topical antifungal medication in combination with strict oral hygiene.

So to briefly recap what we've learned today, the mouth can be divided into the oral vestibule and the oral cavity proper. In the oral vestibule, we have the superior and inferior frenula which we can see here and here. In the oral cavity proper, we've looked at the tongue specifically the body of the tongue which we can see here as well as the hard and soft palates which formed the roof of the mouth. We then saw an extension of the soft palate – the uvula – which is located towards the back of the mouth. Posterior to the uvula, we have this region here called the isthmus of fauces.

Next we had a look at the palatoglossal and the palatopharyngeal arches which are paired folds that extend laterally from the soft palate and form the anterior and posterior boundaries of the palatine tonsils. The palatine tonsils are these lymphoid structures we can see here. Lastly, we looked at the posterior wall of the pharynx and some pathologies relating to the oral cavity.

So that brings us to the end of our overview of the oral cavity. I hope you enjoyed it and thank you for listening.

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