Course and branches of the mandibular branch of the trigeminal nerve.
Hello everyone! Welcome to another anatomy tutorial here at Kenhub. My name is Joao and today we're going to be talking about a nerve – the mandibular nerve. Now, during this tutorial, we will be looking at the mandibular nerve as I mentioned, its branches and a few other related structures.
Now on this image right on your screen, you can see the left side of the skull with a lot of structures here, a lot of muscles, and clearly some nerves here in yellow that we're going to be talking about. Now notice that the skull is cut here on the zygomatic bone and also here on the mandible so we can also see another cut here that we did mainly on the parietal bone then exposes this structure here a bit of the brainstem and you see here another structure known as the trigeminal nerve which will then branch into the focus of this tutorial right here which is the mandibular nerve.
But before we start describing the mandibular nerve let me first show you here this highlight which is essentially highlighting one of the twelve cranial nerves which is named the trigeminal nerve – so this structure right here highlighted in green. And as you can probably remember form our previous tutorials, this is a mixed nerve meaning that it carries both motor and sensory fibers. But what exactly means the name trigeminal? Now, tri- means three or having three which in this case means that the trigeminal nerve has three major branches – the ophthalmic nerve which you see a little bit here, the maxillary nerve which you see a little bit here as well and the focus of our tutorial which is right here – the mandibular nerve.
Now, let's have a closer look at this structure here which you now see highlighted in green. This is known as the trigeminal ganglion. Now the trigeminal ganglion is a group of cell bodies and is located within this cavity right here that I'm showing you and this cavity is known as the trigeminal cave or Meckel's cave. Now, the trigeminal ganglion is a sensory ganglion that contains the afferent cell bodies of the three branches of the trigeminal nerve. And these branches can be seen here on this image a bit more clearly so you can see here the ophthalmic nerve or the ophthalmic branch of the trigeminal nerve right here. Again, you see here the maxillary nerve and, the focus of this tutorial, the mandibular nerve. The ophthalmic and maxillary nerves only carry sensory fibers whereas the mandibular nerve carries both sensory and motor fibers.
Now like I said, we're going to only focus on the mandibular nerve but if you want to learn more about the other nerves – the ophthalmic and the maxillary nerves – then watch other tutorials that we have here at Kenhub.
Let's now have a look at the mandibular nerve in more detail. As I mentioned before, the mandibular nerve carries both sensory and motor fibers and is therefore known as a mixed nerve. This nerve carries sensory fibers from the lower lip and chin up to the temples. The motor branches of this nerve will be then innervating the muscles that help you chew – the muscles of mastication. The mandibular nerve is the largest branch of the trigeminal nerve arising from the lower part of the trigeminal ganglion before exiting the skull through the hole in the skull named as the foramen ovale.
Now we're going to be talking about the different branches of the mandibular nerve starting with this one seen here highlighted in green, this is known as the meningeal branch of the mandibular nerve. Now, just after exiting the skull – remember here through the foramen ovale – the mandibular nerve will give off a few branches that supply the dura mater. You can see that as we zoom in here this is a really, really small branch as you can see. It arises from the lateral part of the mandibular nerve before it enters the skull via another hole known as the foramen spinosum. And see a little bit here on the image this hole that I just talked about – the foramen spinosum.
And as you may have already noticed on this image, you can see here this highlight right here a structure that is entering the foramen spinosum with the nerve that we just talked about – the meningeal branch of the mandibular nerve – this structure is known as the middle meningeal artery. So just a note here on an artery that is entering the foramen spinosum with this nerve. Just a quick note, this is a branch of the maxillary artery then it will accompany the meningeal branch of the mandibular nerve within the skull to then supply blood to the dura mater.
Now let's go back to this highlight of the mandibular nerve where I'm just going to add a quick note here that this nerve splits into two divisions – a small anterior trunk and then a larger one, a posterior trunk. You can see a little bit here on this image – the anterior trunk and the posterior trunk – and we're going to start by looking at the structures or the branches that come from the anterior branch of the mandibular nerve. Right now we see this one highlighted in green which is known as the posterior deep temporal nerve. One note here that the anterior division has five main branches, four of which only carry motor fibers.
This first one that we're looking at – the posterior deep temporal nerve – arises from the anterior division and then ascends posterior as you can see here, so it's ascending. This nerve ascends posterior to this muscle here – the lateral pterygoid muscle – and it will be innervating the temporalis muscle as you can see here. Now, this is the temporalis muscle that is cut here on our image to then expose this nerve that will be innervating it – the posterior deep temporal nerve.
Another branch that carries only motor fibers is this one seen here highlighted in green – the masseteric nerve. The masseteric nerve passes laterally behind this muscle that we see here cut – the lateral pterygoid muscle – then goes all the way down and even crosses the mandibular notch which in this case is cut here but it passes over the mandibular notch. Looking at the name of the nerve you can guess which muscle it's going to be innervating is going to be then the masseter muscle which you see here also in the image but it's slightly cut as you can see but notice how the nerve is in contact with the muscle. And as you remember, this is one of the muscles of mastication.
Another branch of the anterior division is this one that you see here highlighted in green – the lateral pterygoid nerve. You can see it's really small and it's innervating or just in contact as you can see this muscle here that is cut – the lateral pterygoid muscle. And as you probably guess, this muscle of mastication will be then innervated by this nerve.
The next branch we will be looking at now seen here highlighted in green is known as the deep temporal nerve – to be more precise, the anterior deep temporal nerve. As you can see here on this image, this one is ascending as well and is ascending right after or anterior to the lateral pterygoid muscle which you can see here. And like its posterior counterpart that we talked about, the anterior deep temporal nerve will be innervating again this muscle here – the temporalis muscle. Now an important note here is that this nerve can arise directly from the anterior trunk or it may arise from the buccal nerve. In this image, you can see that it's arising from the latter.
And speaking of which, let's move on and talk about the buccal nerve. Now this is the only branch of the anterior division that carries both motor and sensory fibers. You can see here that the nerve is passing through the two heads of the lateral pterygoid muscle and then gives off different branches as it passes through the muscle. You can see here on the image that the nerve then descends anterior to the lateral pterygoid before dividing into a few branches. The buccal nerve carries sensory fibers from the skin over the buccinator muscle which happens to be here also on this image – you can see here a bit of the buccinator muscle. And the buccal nerve also carries sensory fibers from the buccal mucous membrane.
And a very important point that you may be asked about during exams is that the buccal nerve does not provide motor fibers to the buccinator muscle. The buccinator muscle is then innervated by the buccal branch of the facial nerve, also known as cranial nerve number 7.
We will now have a look at the nerves that arise from the posterior trunk or division of the mandibular nerve. The posterior trunk is much larger than the anterior trunk and carries mostly sensory fibers and it divides into three nerves. The first one we will look at is this one seen here highlighted in green – the auriculotemporal nerve. And if you look a bit closely here, you can see that the nerve has two roots that arise on either side of this artery that we talked about – the middle meningeal artery. You can even see that it encircles the artery and after encircling this artery, the two roots then converge in and descend down the posterior cheek. Then if we follow the nerve again, you can see that it then crosses over the mandible before coursing upwards again behind the temporomandibular joint – this joint right here – and then as it continues, it will divide into many branches such as the nerve for the external acoustic meatus for the tympanic membrane, branches for the parotid gland, and anastomosing branches for the facial nerve. Now, the auriculotemporal nerve will be carrying sensory fibers from the skin of the temple, the auricle or the ear, the external acoustic meatus and the tympanic membrane. Not to forget also the parotid gland.
We will now have a look at the next branch of the posterior trunk – the inferior alveolar nerve. The inferior alveolar nerve descends posterior – so as you can see it's behind the lateral pterygoid muscle – then gives off two quite large branches – the mylohyoid nerve and the mental nerve – and some other small branches that form a plexus so called the inferior dental branches. The most distal end of this nerve continues for a short course as the incisive nerve.
We're going to be looking at these branches here. Let's start with this one that you see now highlighted in green here on the image. This nerve is known as the mylohyoid nerve. As you can see here on this image, this nerve travels downwards deep to then the ramus of the mandible that you can also see here before then curving forward. It innervates the mylohyoid muscle and the anterior belly of the digastric muscle – two muscles that you can see here on this image. So the anterior belly of the digastric and the mylohyoid just behind.
Now we're going back again to the image here – the highlight of the inferior alveolar nerve – to show you that after giving off this nerve here – the mylohyoid nerve that we talked about – it will then enter the ramus of the mandible via the mandibular foramen then travels downward and forward through the mandibular canal. Now within the mandible, the inferior alveolar nerve gives off this structure or these branches that you see now highlighted in green which are known as the inferior dental branches. And you can see them highlighted here on the image. These branches will then form a plexus and carry sensory fibers from the mandibular second premolar and the molar teeth.
Finally after giving off the inferior dental branches, the inferior alveolar nerve gives off a third branch known as this one that you see here highlighted in green on the image – the mental nerve. This nerve exits the mandible through this foramen here known as the mental foramen, and then gives off many small branches. The mental nerve will be carrying sensory fibers from the lower lip, the chin and the gingivae also known as the gums of the mandibular anterior teeth and the premolars. It's interesting to note that the mental nerve is sometimes visible through the oral mucosa adjacent to the roots of the premolar teeth.
Now before we continue on with the list of nerves, I just want to show you again this structure that I pointed out on the previous slide, this highlight here, because it's an important structure, this is known as the mental foramen. Now, this is a well-known foramen that's why I'm pointing it out here on this tutorial but this is where then the mental nerve will be exiting the mandible from which you can see here clearly highlighted in green. Now, the mental foramen is usually in line with the second premolar tooth in the majority of individuals. Once the inferior alveolar nerve will then give off the mental nerve, it continues within the mandible and now is usually known as this one here highlighted in green, this is then the incisive nerve. This nerve carries sensory fibers from the mandibular canine and incisor teeth.
Moving on, we will now have a look at the third and final branch of the posterior trunk of the mandibular nerve. This nerve is known as the lingual nerve. The lingual nerve is major sensory branch of the mandibular nerve and emerges from the posterior trunk anterior to the inferior alveolar nerve and then descends posterior as you can see here, just posterior to this muscle here – the lateral pterygoid muscle. It then passes deep to the ramus of the mandible before curving anteriorly.
The most distal part of the lingual nerve which you see now highlighted in green on this image is known as the sublingual nerve. Now, the lingual and sublingual nerves will be carrying sensory fibers from the mucous membrane of the anterior two-thirds of the tongue, from the oral mucosa, and from the lingual gingivae associated with the lower teeth. You can even see a little bit of the tongue here and as the nerve then connected to it. The innervation of the posterior one-third of the tongue is carried then by the glossopharyngeal nerve or cranial nerve number nine.
Below the lingual nerve, there is a ganglion that is suspended from the lingual nerve by two nerve filaments. This is known as the submandibular ganglion. You can see it right here suspending from then the lingual nerve that we talked about. This is one of the four paired sympathetic ganglia in the head. The submandibular ganglion is the site of synapse for parasympathetic fibers and some sympathetic fibers also run through this ganglion but do not synapse within it.
Before we complete this tutorial, I just wanted to end it with a few clinical notes that I believe are important and that are related or connected to the mandibular nerve and its branches. During surgical procedures of the mandible, the mandibular nerve area is usually blocked using a procedure known as mandibular nerve block. Now, this will result in anesthesia of the areas innervated by the mandibular nerve especially the ipsilateral mandibular teeth, the anterior two-thirds of the tongue, floor of the mouth and skin over the lower jaw, posterior cheek, and the temporal area. The way that it's done – the mandibular nerve block – is carried out by injecting local anesthetic around the area of the mandibular nerve.
Dental procedures, however, commonly use a more specific nerve block to produce anesthesia of your teeth. Procedures involving the lower or mandibular teeth will usually involve an inferior alveolar nerve block so a local anesthetic is injected near the mandibular foramen and usually results in blockage of the inferior alveolar nerve and the lingual nerve by diffusion. Now, this causes then anesthesia of the ipsilateral mandibular teeth, the lower lip, chin and parts of the tongue.
Now that you just completed this video tutorial, then it’s time for you to continue your learning experience by testing and also applying your knowledge. There are three ways you can do so here at Kenhub. The first one is by clicking on our “start training” button, the second one is by browsing through our related articles library, and the third one is by checking out our atlas.
Now, good luck everyone, and I will see you next time.