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Overview of the muscles of the pharynx and related structures.
Hello everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial, and in this tutorial, we'll be looking at the muscles of the pharynx. We will be focusing on the origin, insertion, function and innervation of these muscles. And to do so, we're going to be using mainly two images – this one that you see here which is essentially a dorsal view of your pharynx of all the pharyngeal muscles here and then there is also this view here where we just cut them and open them like a book here so we can then see what is happening inside this tube-like structure, the pharynx.
Now, the pharynx is a muscular column that links the nasal and oral cavities – nasal and oral cavities, you can see a little bit here – to the larynx which you see here, also known as the voice box. It also connects to the esophagus – as you can see a little bit here in your neck or starting at your neck. Now, the pharyngeal cavity is a common pathway for food and air and the walls of the pharynx are anterior to the margins of the nasal cavities, the oral cavity and the larynx.
Now, based on these anterior relationships, the pharynx can be divided into the nasopharynx seen here highlighted in green, the oropharynx, and the laryngopharynx. The nasal cavities communicate with the nasopharynx through these holes here known as the choanae. Now, the oral cavity communicates – as you can see here, this is a bit of the oral cavity – communicates with the oropharynx through the oropharyngeal isthmus, and the larynx then communicates with the laryngopharynx through the laryngeal inlet.
In this tutorial, we will discuss the muscles that make up the walls of the pharynx. The muscles of the pharynx are organized into two groups based on the orientation of the muscle fibers. The fibers of the constrictor muscles are orientated in a circular direction relative to the pharyngeal wall and the list includes the superior constrictor muscle, the middle constrictor muscle and the inferior one, whereas the fibers of the longitudinal muscles are oriented vertically, and the list includes the stylopharyngeus muscle, salpingopharyngeus muscle, the palatopharyngeal muscle.
So, now, let's start with the constrictor muscles of the pharynx. The three constrictor muscles are nested within each other from the top down. A good way to visualize the constrictor muscles is as three cone-shaped cups – you can see one of them here highlighted and then another one and another one. So, they are like three cone-shaped cups fitting within each other. Now, this one that you see here highlighted in green is the superior constrictor which fits into the middle constrictor which in turn fits into then the inferior constrictor found here then below.
The superior pharyngeal constrictor muscle is the upper most constrictor muscle of the pharynx. This quadrilateral constrictor muscle consists of pterygopharyngeal part which has the origin on the posterior margin of the medial pterygoid plate and hamulus. There is also a buccopharyngeal part which has its origin on the pterygomandibular raphe.
Another one, the third part, is the mylopharyngeal part which originates at the alveolar process of the mandible. And, finally, a glossopharyngeal part which originates at the fibers from the tongue. This muscle has an insertion on the pharyngeal tubercle and the pharyngeal raphae. Receives innervation via the pharyngeal plexus from the pharyngeal branch of the vagus nerve. The function of the superior pharyngeal constrictor is to then constrict the upper portion of the pharynx pushing and conveying the food bolus inferiorly.
Next, we're going to be seeing here a bit further below, the middle pharyngeal constrictor which is a fan-shaped muscle that proximally attaches to the stylohyoid ligament and the greater and lesser horn of the hyoid bone. It attaches distally to the pharyngeal raphe. This muscle? (4:41) is innervated by the pharyngeal plexus – by a branch of the vagus nerve – and has its function to then constrict the middle portion of the pharynx contracting upon the food bolus and conveying it then forward towards the esophagus.
The last of the constrictor muscles that you see now highlighted in green is then the inferior pharyngeal constrictor muscle. As for the origin, the muscle will start then at the oblique line of the thyroid cartilage and also at the lateral aspect of the cricoid cartilage. Then, it will be inserting on the pharyngeal raphae. It is the thickest of the three constrictor muscles of the pharynx and it functions to constrict the lower portion of the pharynx. Now, this muscle is comprised of two parts – a thyropharyngeal part and a cricopharyngeal part.
So, let's take a quick look at the two parts of the inferior pharyngeal constrictor muscles starting with this one. This is the thyropharyngeal part of the inferior pharyngeal constrictor which originates from the oblique line of the thyroid cartilage. It is innervated by the pharyngeal plexus by branches of the tenth cranial nerve, the vagus nerve. The other part is this one that you now see highlighted, the cricopharyngeal part of the inferior pharyngeal constrictor, which originates from the cricoid cartilage between the cricothyroid muscle and the articular facet for the inferior horn of the thyroid cartilage. This part is innervated by a branch of the vagus nerve via the pharyngeal plexus as well.
So, now that we have discussed the constrictor muscles of the pharynx, I just want to quickly mention that these muscles have a common important function. When they contract sequentially from top to bottom as if you, when you're swallowing, they move the food bolus through the pharynx and into your esophagus. Before we move on to the longitudinal muscles of the pharynx, let's have a look at this structure here that serves as an insertion point for the constrictor muscles and that is the pharyngeal raphe.
The pharyngeal raphe is a connective tissue band between the right and left pharyngeal muscles. It extends posteriorly in the midline and joins the two sides of the pharyngeal wall posteriorly. It is attached to the pharyngeal tubercle superiorly and extends to the level of C6 inferiorly where it blends with the posterior wall of the esophagus.
So, now, let's look at the longitudinal muscles of the pharynx. As we will see, these three muscles are named according to their origins. The first of these three muscles that we will look at is this one seen here highlighted in green which is the stylopharyngeus muscle. The stylopharyngeus muscle arises from the medial aspect of the base of the styloid process and passes between the superior and middle pharyngeal constrictor muscles spreading into the pharyngeal wall, the thyroid cartilage and the epiglottis. This muscle elevates the pharynx and expands it laterally. The stylopharyngeus muscle receives motor innervation from the ninth cranial nerve, also known as the glossopharyngeal nerve.
Next, we're going to be seeing this muscle here highlighted in green which is known as the salpingopharyngeus muscle which originates from the cartilage of the auditory tube which you can see here – the two cartilages of the auditory tubes. They are also known as the pharyngotympanic tubes. And it will insert – this salpingopharyngeus – it will insert on the lateral wall of the pharynx. This muscle can be seen as an elevation or fold located posterior to the torus tubarius known as the salpingopharyngeal fold. As for the function of the salpingopharyngeus, it is there to then raise the pharynx and larynx during swallowing and prevent the backward displacement of the levator palatini muscle. As a reminder here that the salpingopharyngeus muscle is innervated by the vagus nerve via the pharyngeal plexus.
The next muscle we're going to be highlighting here is the palatopharyngeus muscle. Now, this is the final longitudinal muscle of the pharynx that we will be looking at and originates at the palatine aponeurosis at the posterior border of the hard palate in the roof of the mouth. It inserts on the posterior aspect of the lamina of the thyroid cartilage. This paired muscle is going to be then elevating the pharynx in order to close it off from the nasopharynx during swallowing. Receives motor innervation from the pharyngeal plexus specifically from the vagus nerve via the pharyngeal plexus.
So far we have covered the muscles of the pharynx, now let's move on and look at some of the surrounding structures that can be seen in this region specifically also on this image. Firstly, let's look at the pharyngobasilar fascia as you can see here highlighted in green which is also known as the pharyngeal aponeurosis. This aponeurosis is located between the mucous and muscular layers of the pharynx. It is attached to the basilar portion of the occipital bone and the petrous part of the temporal bones. Reinforces the pharyngeal wall where the muscle is deficient.
From the posterior aspect of the pharynx, we see there two small cartilaginous structures that are cartilaginous parts of the auditory tube. The auditory tube, also known as the Eustachian tube, is also known as the pharyngotympanic tube which extends from the lateral wall of the middle ear to the nasopharynx. An opening for the auditory tube can be seen in the nasopharynx, cartilaginous part of the Eustachian tube can be seen as an elevation in the nasopharynx beneath the mucosa known as the torus tubarius.
Another cartilaginous structure that we see from this posterior view is the thyroid cartilage. It is the largest of the laryngeal cartilages and it is located in front of the larynx above the thyroid gland which you can see a little bit here, the thyroid gland. This cartilage is comprised of two halves that meet in the middle to form then the laryngeal prominence – something that you can see a bit more clearly in men known as the Adam's apple. It has a superior thyroid notch and inferior thyroid notch and inferior horn and the superior horn which are not visible from this perspective but nonetheless must be noted as far as structure of this cartilage is concerned but we're going to be covering it on other tutorial – just keep that in mind.
Also, on the lateral surface of the thyroid cartilage, there is an oblique line which is not clearly seen from this perspective from which the thyrohyoid muscle and the inferior pharyngeal constrictor muscle originates from – so just a reminder here. Immediately superior to the thyroid cartilage, we see highlighted here in green, the greater horns of the hyoid bone on the left and right sides from this posterior aspect of the pharynx. These structures project backwards from the outer border body of the hyoid bone providing attachment for the hyoglossus muscle and the middle pharyngeal constrictor muscle on their upper surface.
Finally, this structure that we see here in the most inferior part of this image is the esophagus. The esophagus extends from below the cricoid cartilage at approximately the level of C6 to the cardiac part of your stomach. This is a fibromuscular tube which serves as a passage for food to go from the oral cavity to the stomach and the esophagus is lined by mucosa – just some information to add here about this important structure.
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Now, good luck everyone, and I will see you next time.