# Pharynx II : External features - Constrictors

https://www.youtube.com/watch?v=VxL260ouHQs

[00:17] Hello viewers, welcome to our channel dissection of human body.
[00:21] In the last video, we discussed about the internal features of pharynx.
[00:26] Today, we are going to discuss about the external features of pharynx, especially the musculature, the constrictors of the pharynx.
[00:35] My colleague, Dr. Aparna Muralidharan, will discuss about it.
[00:40] Over to her.
[00:42] Hello viewers.
[00:42] In this video, we will discuss the anatomy of pharynx.
[00:49] The subdivisions of pharynx and features of the interior of pharynx has already been explained in another video.
[00:56] In this video, let us see some important relations of pharynx, as well as the musculature of pharynx.
[01:03] So, first let me give you an orientation to this specimen.
[01:07] Here, and a cut is made through the anterior aspect of the foramen magnum.
[01:13] And we have removed the vertebral column with the spinal cord.
[01:16] We have removed.
[01:18] The prevertebral muscles, as well as the fascia that covers the posterior aspect of this muscular tube.
[01:26] So, this muscular tube is the pharynx, and the fascia that covers the posterior aspect of pharynx, and all the muscles that surround it, is called as a buccopharyngeal fascia.
[01:37] So, in this specimen, we are seeing the musculature directly, because the buccopharyngeal fascia that covers it has been removed.
[01:45] Let us see some important relations in this specimen.
[01:47] So, as you can see here, on either side of the pharynx, on either side, we can see so many blood vessels and nerves.
[01:57] So, the important lateral relation to most of the pharynx is formed by the contents of the carotid sheath, as well as the styloid apparatus.
[02:08] The carotid sheath contents that you can see here include the common carotid artery, the internal carotid artery.
[02:15] This is the internal jugular vein, and this is the vagus nerve.
[02:19] Related posteromedial to the carotid sheath, we are able to see the sympathetic chain, the cervical sympathetic chain.
[02:28] What I'm holding is the superior cervical ganglion.
[02:31] Coming a little lower down, we can see that on either side of the pharynx, the lateral lobes of the thyroid gland is also related.
[02:42] So, what is the extent of pharynx?
[02:44] As you can see here, it extends from the base of skull till this level.
[02:48] So, this corresponds to the lower border of cricoid cartilage ventrally, or the lower border of the C6 vertebra dorsally.
[03:00] At this area, we can see that the tube narrows down.
[03:04] So, this point demarcates the pharynx above from the esophagus below.
[03:10] So, this is the pharyngoesophageal junction, which is the narrowest part of the GIT, second to appendix.
[03:18] So, as you can see here, pharynx is a
[03:21] Musculomembranous tube that extends from the base of skull till the pharyngoesophageal junction at the level of lower border of C6 vertebra.
[03:30] What do you think is the shape of the pharynx?
[03:32] From the specimen, it's clear that pharynx is a dilated funnel-shaped tube.
[03:39] So, as I said, the buccopharyngeal fascia is removed, and we are exposing the musculature.
[03:42] So, what are the muscles of pharynx?
[03:46] In contrast to the rest of the GIT, in pharynx, we have inner longitudinal muscle coat and outer circular muscle coat.
[03:56] In the remaining part of GIT, there is inner circular muscle coat and an outer longitudinal muscle coat.
[04:03] The inner longitudinal muscle coat of the pharynx constitutes of three muscles, namely salpingopharyngeus, palatopharyngeus, and stylopharyngeus muscles.
[04:17] All the three muscles, they arise from the respective bony prominences and they.
[04:22] Enter into the pharynx at narrow constrictions present within the musculature and they all attach to this cartilage.
[04:30] This is the posterior border of the thyroid lamina.
[04:33] So, these muscles will be attached to the posterior border of the thyroid lamina.
[04:40] What we can see clearly here is the outer circular muscle coat, which is also called as constrictors of pharynx.
[04:48] The constrictor muscles of pharynx include the superior constrictor, middle constrictor, and inferior constrictor.
[04:57] In the posterior aspect, we are not able to see the three constrictor muscles separately because each one below the other overlaps the lower part of the constrictor above.
[05:07] That is, the upper fibers of the middle constrictor will overlap the lower fibers of superior constrictor, upper fibers of the inferior constrictor will overlap the lower fibers of middle constrictor.
[05:21] And then, we can see a midline white.
[05:24] Raphe here.
[05:25] This raphe is called as the pharyngeal raphe that attaches above to a tubercle present on the under surface of the basilar occiput called as the pharyngeal tubercle.
[05:36] So, this pharyngeal raphe extends from the pharyngeal tubercle above and it terminates at the pharyngoesophageal junction here.
[05:45] All the muscles, that is, the constrictor muscles of the pharynx, are inserted onto this fibrous raphe.
[05:58] So, let us see the attachments of each of these constrictor muscles.
[06:01] So, first let us see the attachments of superior constrictor.
[06:12] This is the lateral aspect of the infratemporal fossa.
[06:17] So, what you are seeing here, this white line, this is the pterygomandibular raphe that attaches above to the.
[06:24] Pterygoid hamulus and below to the posterior end of the mylohyoid line, which we are not able to see here because the mandible has been removed.
[06:35] This pterygomandibular raphe gives attachment anteriorly to this muscle.
[06:40] This muscle, which is pierced by the parotid duct here, is the buccinator muscle.
[06:44] And the same raphe attaches posteriorly to the superior constrictor muscle.
[06:51] So, this muscle that you can see here is the superior constrictor, which attaches to the medial pterygoid plate, pterygoid hamulus, the pterygomandibular raphe, to the mandible, that is to the posterior end of the mylohyoid line, and it also attaches to the sides of the tongue.
[07:11] The superior constrictor muscle fibers, they sweep posteriorly and superiorly, and these are the superior fibers of the superior constrictor muscle.
[07:22] They sweep.
[07:25] Upwards and they get attached onto the pharyngeal tubercle.
[07:29] The intermediate fibers and lower fibers will attach to the pharyngeal raphe.
[07:36] So, this is the attachments of the superior constrictor muscle.
[07:41] As you can see here, this is the superior fibers of the superior constrictor.
[07:46] There is a deficiency of musculature above this level.
[07:50] So, above the superior border of the superior constrictor, as you can see here, it is a white fascia.
[07:57] We have already removed the buccopharyngeal fascia that covers here.
[08:01] Deep to the superior constrictor, we have another fascia that covers the muscles of the pharynx.
[08:06] This is called as the pharyngobasilar fascia.
[08:09] So, the area above the superior border of superior constrictor, which is actually a weak space, is covered on the inside by the pharyngobasilar fascia, and on the outside by the buccopharyngeal fascia.
[08:23] And this deficient space is called as the sinus.
[08:25] Of Morgagni.
[08:28] Through the sinus of Morgagni, four structures enter and leave the pharynx.
[08:34] So, this is one important structure, this white-colored structure is an important structure that passes through this deficiency.
[08:40] This is the cartilaginous part of the Eustachian tube.
[08:45] Along with this Eustachian tube, we will also have levator veli palatini muscle, ascending palatine vessels, and palatine branch of the ascending pharyngeal vessels.
[08:57] So, that is the sinus of Morgagni.
[09:00] Now, let us see the attachments of middle constrictor.
[09:06] Let us first understand this bone.
[09:08] This is the greater horn of the hyoid bone.
[09:11] The membrane below it is the thyrohyoid membrane, and this is the middle constrictor muscle.
[09:18] So, the middle constrictor muscle also has two origins.
[09:20] It has a part that arises from the greater horn of the hyoid bone.
[09:26] A small part also arises from the stylohyoid ligament, which will be attached to the lesser horn of the hyoid bone.
[09:33] So, these two parts of middle constrictor are called as ceratopharyngeus and chondropharyngeus muscles respectively.
[09:40] So, ceratopharyngeus arises from the greater horn of the hyoid and chondropharyngeus arises from the stylohyoid ligament.
[09:49] The middle constrictor muscle forms a part of the floor of the carotid triangle in this region and the fibers again sweep posteriorly.
[10:03] So, the middle constrictor muscle fibers sweep posteriorly and upper fibers ascend up, middle fibers will be horizontal, and the lower fibers will descend down, and they insert onto the pharyngeal raphe.
[10:14] The uppermost fibers may reach as far as the pharyngeal tubercle, like the superior constrictor.
[10:22] So, again, the lower fibers of the superior constrictor muscle is
[10:26] Overlapped by the upper fibers of the middle constrictor posteriorly.
[10:32] But, on the sides, there is a deficiency between the superior constrictor muscle and the middle constrictor muscle.
[10:39] Through this space, we have this nerve and this muscle entering the pharynx.
[10:45] So, this muscle arises from the styloid process along with this nerve.
[10:51] So, this muscle is called as the stylopharyngeus muscle, and the nerve that supplies it and accompanies it to enter the pharynx is the glossopharyngeal nerve.
[10:59] So, the space between the superior constrictor above and middle constrictor below is traversed by the stylopharyngeus muscle and the glossopharyngeal nerve.
[11:11] Now, let us see the parts and attachments of the inferior constrictor of pharynx.
[11:18] The inferior constrictor muscle, which is the largest of the three constrictors, has two parts.
[11:25] So, it has a part that arises from this.
[11:28] Cartilage.
[11:30] This is the thyroid cartilage.
[11:32] And it has a part that arises from this cartilage, which is a cricoid cartilage.
[11:35] So, this is the oblique line of the thyroid cartilage.
[11:39] The oblique line of the thyroid cartilage gives rise to some part of this muscle.
[11:43] So, this part of inferior constrictor is called as the thyropharyngeus part.
[11:48] And this part of the inferior constrictor that arises from the lateral aspect of the anterior arch of the cricoid is called as cricopharyngeus part.
[11:57] Now, what happens to the fibers posteriorly?
[12:01] The thyropharyngeus part again upper fibers ascend up, middle fibers run horizontally, and the lower fibers descend down, and the upper fibers overlap the lower fibers of middle constrictor, and it will be attached to the pharyngeal raphe.
[12:17] Whereas, cricopharyngeus muscle is different from all the other constrictors in that it does not attach to the pharyngeal raphe.
[12:26] Instead, it is continuous with the cricopharyngeus muscle of the other side, acting like a.
[12:31] Sphincter at this area.
[12:35] Now, between the middle constrictor that takes origin from the greater horn and the inferior constrictor that arises from the thyroid cartilage, there is again a deficiency, which is filled in by the thyrohyoid membrane.
[12:49] And this will be pierced by the nerve here, which is a branch of the vagus along with the artery.
[12:56] So, this nerve is the internal laryngeal branch of the superior laryngeal nerve, which is a branch of the vagus.
[13:03] And this vessel is the superior laryngeal vessel, which is a branch of the superior thyroid artery.
[13:10] So, these two structures pierce the thyrohyoid membrane to enter inside the pharynx, where it will be related submucosally in the piriform fossa.
[13:20] The internal laryngeal nerve and superior laryngeal vessels will supply the upper part of the larynx as far as the vocal cords.
[13:28] Now, as I said, there is a thyropharyngeus and a cricopharyngeus.
[13:32] Part for the inferior constrictor muscle.
[13:35] The two parts are continuous.
[13:38] But, functionally, when there is a neuromuscular incoordination between these two, there may be a deficiency in the junction between the two.
[13:48] This deficiency is called as Killian's dehiscence.
[13:52] So, in people with neuromuscular incoordination between these two, when the pressure inside the pharynx increases, as during swallowing, or in trumpet blowers, or glass blowers, what happens would be the mucosa of the pharynx will protrude out through this deficiency, that is the Killian's dehiscence.
[14:14] This mucosal protrusion will present as a swelling in the neck between the thyropharyngeus and cricopharyngeus parts.
[14:21] This diverticulum is called as pharyngeal diverticulum, also called as Zenker's diverticulum.
[14:38] Now, below the level of the inferior constrictor, also, there is a deficiency above the level of esophagus.
[14:42] Through this deficiency, we have this nerve that lies in the tracheoesophageal groove, along with this vessel, entering into the laryngopharynx, and then into the larynx.
[14:55] So, this is the recurrent laryngeal nerve.
[14:57] This is the left recurrent laryngeal nerve that winds around the arch of aorta, reaches the tracheoesophageal groove, and then it enters the larynx.
[15:06] This is the right recurrent laryngeal nerve that winds around the right subclavian artery, and then it enters the larynx.
[15:15] And this is the inferior laryngeal vessel, which is a branch of the inferior thyroid artery, which supplies the lower part of the larynx.
[15:26] So, to summarize, pharynx is a musculomembranous tube.
[15:29] The muscles are made of an inner longitudinal and an outer circular muscle coat.
[15:33] The inner longitudinal muscles include.
[15:38] Stylopharyngeus, salpingopharyngeus, and palatopharyngeus.
[15:42] And the outer circular muscle coat includes superior constrictor, middle constrictor, and inferior constrictor.
[15:49] There are some deficiencies between these constrictors that allow some structures to enter and leave the pharynx.
[15:54] Above the level of superior constrictor is the sinus of Morgagni, that transmits auditory tube along with levator veli palatini, ascending palatine vessels, and palatine branch of ascending pharyngeal vessels.
[16:09] The space between the superior and middle constrictor transmits glossopharyngeal nerve along with stylopharyngeus muscle.
[16:16] This is the stylopharyngeus muscle.
[16:19] The space between middle constrictor and inferior constrictor transmits internal laryngeal nerve and superior laryngeal vessels.
[16:28] And the space below the inferior constrictor transmits recurrent laryngeal nerve and inferior laryngeal vessels.
[16:41] Now, what is the nerve supply to these musculature?
[16:42] The nerve supply to these muscles is derived from the pharyngeal plexus.
[16:47] And the pharyngeal plexus will be formed over the middle constrictor muscle deep to the buccopharyngeal fascia that covers it.
[16:54] So, it is derived from the pharyngeal branches of vagus, cranial root of the accessory nerve, glossopharyngeal nerve, as well as from the cervical sympathetic chain.
[17:07] Thank you.
[17:31] Hey.