Hello everyone! It's Megan from Kenhub here, and welcome to our tutorial about the cross section at the level of the tongue. Knowledge of this cross section is especially important when looking at MRI or CT scans of the head. So hopefully by the time we finish this tutorial, you have a clearer idea of the structures we can see at this level. First, let's remind ourselves that when we look at cross sections, we're looking from the feet upwards towards the head. This means that this side is the right hand side of the body, this side is the left hand side of the body, this is anterior or the front of the body, and this is posterior or the back of the body.
Before we begin, I'll also introduce you to this icon we can see here which we'll feature throughout the video. You can use this to remind yourself of the level of the body we're looking at which is represented by this line here. So let's start this tutorial by looking at one of the more obvious structures we can see at this level. If we look at the anterior aspect of this cross section, we can see this large green structure here which as you probably guessed is the tongue. This muscular structure is the organ of deglutition, taste and speech and forms the floor of the oral cavity. It consists of an oral part which is located anteriorly and a pharyngeal part which is located more posteriorly.
As we can see in the image on the right, the dorsum of the tongue is curved. This dorsal surface is covered by papillae and some of these contain taste buds. Anterior and lateral to the tongue, we can see some teeth. The teeth highlighted in green are the first premolar teeth and, as we can see here, they're the fourth teeth from the midline. In both the cross section and this image, we can also see the canine teeth as well as the right incisors. However, we can't see the left incisors in the cross section.
Posterior to the tongue, we see these paired structures here which are the palatine tonsils. These masses of lymphoid tissue are located in the lateral part of the oropharynx. As you can see in this illustration, the medial surface of these tonsils has a pitted appearance. Surgical removal of the tonsils which is also called tonsillectomy is performed when tonsillitis occurs frequently or does not respond to other treatments.
Moving further posteriorly, we can see this bony structure here which is the second cervical vertebra. It's the second out of seven cervical vertebrae and is also known as the axis. Its structure is slightly different from the other cervical vertebrae because of this process here which is called the dens. In the middle of the second cervical vertebra is the spinal cord which we can see here highlighted in green. It extends from the medulla of the brainstem down the vertebral column until the intervertebral space between the first and second lumbar vertebrae. This nervous tissue is part of the central nervous system and plays an essential role in the functioning of the trunk and limbs. It's also a huge clinical importance because it's a major site of traumatic injury.
If we move posteriorly once again, we can see this long thin structure here which is the nuchal ligament. This ligament originates at the external occipital protuberance of the skull and then runs downwards posterior to the spinous processes of the cervical vertebrae. In the cross section, we can see that the nuchal ligament is attached to the spinous process of C2. The role of the nuchal ligament is to provide support and stability to the head during the movements of the body.
Another bony structure we can see in this cross section is the ramus of the mandible. The mandible is a bone of the skull and is also known as the jawbone. It forms the lower part of the jaw and consists of a body and a ramus. The ramus is the upper part of the mandible and there's one on each side. Posterolateral to the rami of the mandible are the parotid glands. These irregularly-shaped masses are the largest of three salivary glands in the head. They are usually pyramidal-shaped and they lie between the rami of the mandible and the sternocleidomastoid muscles.
So let's move on to looking at the muscles of this cross section starting anteriorly and working our way backwards. The first muscle we'll look at is the orbicularis oris muscle. This muscle surrounds the mouth and is circular in shape which caused this muscle to originally be thought of as a sphincter. However, it's actually composed of four parts which join together to form the circular shape.
Posterior and slightly lateral to the orbicularis oris is the buccinator muscle. There are two of these muscles – one on the right side of the tongue and one on the left side of the tongue. In the image on the right, we can see that the buccinator is located over both the maxilla and the mandible of the skull. Posterolateral to the buccinator muscle is the masseter muscle which we can see here highlighted in green. This muscle of mastication is located on the lateral aspect of the face over the ramus of the mandible.
If we move medially, we can see the medial pterygoid muscle. In the cross section, we can see that the masseter muscle is located lateral to the ramus of the mandible whereas the medial pterygoid is located medial to it. As we can see in this image on the right, this muscle is attached to the mandible. Its main action is to assist with elevating and protruding this bone. In between the two medial pterygoid muscles is the superior pharyngeal constrictor muscle. There are actually two of these muscles but in the cross section, it looks like there's only one because they join together in the middle of the pharynx at the median raphe. These muscles help with the passage of a bolus of food down the esophagus.
If we move laterally, we can see the digastric muscles which are located posterior to the medial pterygoid muscles. This muscle is called digastric because it consists of two bellies which we can see here highlighted in green. Interestingly, each of these bellies is supplied by a different cranial nerve. Medial and slightly posterior to the digastric muscles are the levator scapulae muscles which are located on either side of the second cervical vertebra. In this image which is from a posterior view, we can see that this muscle originates from the transverse processes of the first four vertebrae as well as attaching to the scapula. If we look back at the cross section, we can see that the levator scapulae are also attached to the transverse processes of C2.
Moving out laterally, we come across another muscle – the sternocleidomastoid. The name of this muscle comes directly from its origin and insertion sites. It originates from the sternum and the clavicle and it inserts into the mastoid process of the temporal bone. Like I mentioned earlier, this muscle is found posterior to the parotid gland. The sternocleidomastoid is an important muscle in the neck that forms the boundaries between the anterior and posterior triangles. These triangles are very important to know in clinical practice as they help you identify and locate many other structures in the neck.
Medial to the sternocleidomastoid is the splenius capitis muscle. As we can see in the cross section, this muscle is located on both sides of the body. This is another important muscle of the neck as it's one of the muscles that forms the floor of the posterior triangle. This muscle originates from the back of the skull and deviates medially to attach to the cervical and thoracic vertebrae. A small trick to keep in mind is that capitis means "head" in Latin which is a good way to remember that this muscle attaches to the skull.
Moving medially, we can see another muscle that is located lateral to the posterior aspect of the second cervical vertebra. This muscle is the obliquus capitis inferior and it's the only muscle that has capitis in its name that doesn't actually attach to the head. Posterior to the obliquus capitis inferior is the rectus capitis posterior major which we can see here highlighted in green. This is another muscle of the posterior neck that attaches to the occipital bone of the skull. Moving further backwards, we can see this muscle here which is the semispinalis capitis muscle. Like the rectus capitis posterior major, this muscle originates from the occipital bone. It then travels down the posterior neck lateral to the spinous processes of the vertebrae.
The final major muscle that we see in this cross section is the trapezius muscle. As you can see in the picture on the right, this is a major and very extended muscle of the back, however, it's also the most superficial of the posterior muscles in this cross section which is why it appears so thin. This muscle is called the trapezius because it is similar in shape to a trapezium or trapezoid.
So I know you're probably tired after looking at all the different muscles of this cross section but I promise that we're nearly finished. We just need to cover a few veins that we can see in this cross section. The first of which is the facial vein which is located lateral to the buccinator muscles. Here we can see the right and left facial veins which are the main veins of the face and travel obliquely downwards from the side of the nose. Within the parotid gland and quite easy to distinguish, we can see another vein which is the retromandibular vein. This vein is formed by the union of the maxillary and superficial temporal veins.
Finally, the last vein that we're going to see in this section is the internal jugular vein which is located posterior to the medial pterygoid muscles and medial to the parotid glands. The internal jugular vein is of course a very important vein that collects blood from the brain and parts of the face and neck. It's also important in clinical practice as it's used to measure the jugular venous pressure or JVP which estimates the pressure of the right atrium. As it drains blood from several regions, it's quite a large vessel and therefore damage to the internal jugular vein could cause significant blood loss which could potentially lead to hypovolemic shock and even death.
So on that cheery note that brings us to the end of our difficult but hopefully interesting tutorial on the cross section at the level of the tongue. Identifying structures in cross section can be tricky but you can practice by trying our quiz on this cross section on our website. This skill will be extremely useful in your medical career when looking at CT or MRI scans. I hope you enjoyed the tutorial and thank you for listening.
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.