Muscular Layers of the Pharynx

00:01 If we take a posterior look at the pharynx, we will see a fibromuscular tube composed of different layers that appear to be telescoping into each other.

00:11 Well these layers of the pharynx represent its external muscular layer.

00:17 As I mentioned before, the muscular layer of the pharynx is supported anteriorly and internally by the pharyngobasilar fascia, which hangs down from the base of the skull, and this is the first layer that is visible right below the basis occiput.

00:33 The next layers that are visible, external and inferior to this fascia are the external constrictor muscles of the pharynx.

00:41 Let's take a look now at these particular muscles.

00:45 The first and most superior muscle of this group is the superior constrictor.

00:51 This muscle takes origin from the pterygoid hamulus, the pterygomandibular raphe, the mylohyoid line of the mandible, and from the side of the tongue as well.

01:04 Its fibres curved posteriorly to attach to the median pharyngeal raphe.

01:10 Below in overlapping this muscle is the middle constructor.

01:14 The middle constructor is a large fan shaped sheet of muscle that takes this origin mainly from the cornu and the body of the hyoid bone, as well as from the stylohyoid ligament.

01:27 Its fibres also insert posteriorly into the median pharyngeal raphe.

01:34 Last but not least, the pharyngeal muscles is the inferior constrictor.

01:39 This muscle also overlaps the middle constrictor externally.

01:44 This muscle can be divided into two parts based on its attachments.

01:49 The first part is the thyropharyngeus which is formed from oblique fibres and arises mainly from the oblique line of the thyroid lamina.

02:00 And goes on to insert into the median pharyngeal raphe.

02:04 And the second part is the cricopharyngeus which is formed by transverse fibres and arises mainly from the cricoid cartilage, and In thouroughly, it goes on to blend in with the circular esophageal fibres.

02:21 These three muscles are all innervated by the pharyngeal Plexus of nerves formed by the branches of the vagus, and glossopharyngeal nerves, as well as by the sympathetic Plexus.

02:34 Furthermore, all these muscles participate in the constriction of their respective parts of the pharynx during swallowing.

02:43 Additionally, the cricopharyngeal, as well as the lower thyropharyngeal fibres of the inferior constrictor also function to close the esophageal sphincter.

02:55 One additional topic I would like to bring to attention in this lecture before we move on to the internal laryngeal muscles are the potential spaces located between the overlaps of the external pharyngeal muscles.

03:11 The first of these spaces, I have already introduced, this is the sinus of moregagni, as you should remember this is a space between the upper border, the superior constrictor and the base of the skull, which is filled in by the thickening of the pharyngeal basilar fascia.

03:30 Through this space past several important structures, the most important of which is the pharyngotympanic tube, which we will discuss later.

03:41 The second space is located between the superior and middle constrictor muscles.

03:47 This space allows for the passage of the glossopharyngeal nerve and the stylopharyngeus muscle.

03:56 The third space is located between the middle and inferior constructors here superior laryngeal vessels and the internal laryngeal nerve paths.

04:08 And lastly, deep to the inferior constrictor enter the recurrent laryngeal nerve and inferior laryngeal vessels.

04:18 And the last space I would like to touch upon is not really a space at all, but rather a potential location of a false diverticulum.

04:28 As you should already know from the previous slide, the inferior constructor has two parts, the thyropharyngeus and the cricopharyngeus.

04:38 Between these two parts lies a relatively weak unsupported mucosa.

04:43 This weak region is termed Killians Dehiscence, which can be a site of diverticulum formation, if the slowing mechanism of the pharynx becomes this coordinated.

04:57 Now we are going to discuss the last group of muscles in relation to the pharynx.

05:01 The internal muscle layer.

05:03 This group of muscles consists of three elevator muscles -- the stylopharyngeus, the salpingopharyngeus and the Palatal pharyngeus.

05:16 The stylopharyngeus is a long slender muscle that arises from the styloid process and descends along the side of the pharynx.

05:26 On its descent, it passes in between the superior middle constrictors and then spreads out in thoroughly to merge with fibres of the palatal pharyngeus.

05:36 In thoroughly, it also attaches to several structures, including the thyroid cartilage.

05:42 Another thing worth noting is that along with the stylopharyngeus muscle, we also have coursing with it the glossopharyngeal nerve, and this muscle is the only muscle of the entire pharyngeal musculature that is innervated by the glossopharyngeal nerve and not by the pharyngeal Plexus of nerves.

06:02 The salpingopharyngeus is another elevator of the pharynx.

06:07 It originates from the cartilage of the Eustachian tube, and passes inferiorly to blend in with the palatal pharyngeus muscle.

06:16 This muscle in addition to elevating the pharynx also participates in the opening of Eustachian tube.

06:23 And now the last muscle in this group, the palatal pharyngeus.

06:27 This muscle originates from the Palatine Aponeurosis, and the pterygoid hamulus.

06:34 And descends down to attach to the lateral and posterior walls of the pharynx and the thyroid cartilage.

06:42 The palatal pharyngeus pulls the pharynx up forwards medially and also approximates the palatal pharyngeus arches during swallowing.

06:52 The internal musculature is all innervated by the pharyngeal plexus with the exception of the stylopharyngeus muscle, which once again derives its innervation from the glossopharyngeal nerve.

07:04 Additionally, to sum up the basic function of the internal muscle layer of the pharynx, it can simply be said that all these muscles elevate the pharynx.

07:13 This concludes our discussion of the pharyngeal musculature.

07:17 And now we will move on to discussing the sectional anatomy of the pharynx and the structures located within it.