Description

Pharynx: Anatomy, Layers, and Muscles

This video covers the parts of the pharynx, the layers of the pharyngeal wall, and the muscles involved in swallowing and phonation.

1. Pharynx Overview:

• Muscular tube measuring 12 to 15 cm in length.
• Located behind the nasal and oral cavities, connecting to the esophagus.

Divisions:

• Nasopharynx (Pars Nasalis)
• Oropharynx (Pars Oralis)
• Laryngopharynx (Pars Laryngis)

2. Nasopharynx (Pars Nasalis):

• Located at the level of C1-C2.
• Structures:
  • Vault of Pharynx (Fornix Pharyngis).
  • Attachment Points:
    • Pharyngeal Tubercle of the Occipital Bone (Tuberculum Pharyngeum).
    • Petrooccipital Fissure (Petrooccipital Synchondrosis).
    • Inferior Surface of Petrous Part (Temporal Bone).
    • Medial Lamina of Pterygoid Process.
  • Openings:
    • Choana (Internal Nose).
    • Auditory Tube (Tuba Auditiva).
    • Pharyngeal Opening of the Auditory Tube (Ostium Pharyngeum Tubae Auditivae).
    • Cushion of the Auditory Canal (Torus Tubarius).
    • Pharyngeal Recess (Recessus Pharyngeus).
  • Tonsils:
    • Pharyngeal Tonsils / Adenoids (Tonsilla Pharyngealis).
    • Tubal Tonsils (Tonsilla Tubaria).

Auditory Tube Overview:

• Connects the nasopharynx to the middle ear.
• Function:
  • Equalizes pressure in the middle ear.
  • Drains fluids from the middle ear.

3. Oropharynx (Pars Oralis):

• Located at the level of C3-C4.
• Bordered by the soft palate superiorly and the epiglottis inferiorly.
• Communicates with the oral cavity via the oropharyngeal isthmus (Isthmus Faucium).

4. Laryngopharynx (Pars Laryngis):

• Located at the level of C5-C6.
• Continues into the larynx through the laryngeal inlet (Aditus Laryngis).
• Contains the piriform fossa (Recessus Piriformis), an important structure in swallowing.

5. Layers of the Pharyngeal Wall:

Tunica Mucosa:

• Lined by different epithelium based on location:
  • Nasopharynx: Respiratory epithelium (pseudostratified columnar with cilia and goblet cells).
  • Oropharynx & Laryngopharynx: Stratified squamous non-keratinized epithelium.

Tela Submucosa:

• Contains connective tissue, blood vessels, lymphatic vessels, and glands.

Tunica Muscularis:

• Composed of two muscle layers for peristalsis.
  • Internal Circular Muscle Layer (Stratum Circulare).
  • Outer Longitudinal Muscle Layer (Stratum Longitudinale).

Tunica Adventitia:

• Connective tissue covering the pharynx externally.

6. Muscles of the Pharynx:

External Pharyngeal Muscles (Pharyngeal Constrictors)

• Superior Pharyngeal Constrictor (Musculus Constrictor Pharyngis Superior).
• Middle Pharyngeal Constrictor (Musculus Constrictor Pharyngis Medius).
• Inferior Pharyngeal Constrictor (Musculus Constrictor Pharyngis Inferior).

Internal Pharyngeal Muscles (Pharyngeal Elevators)

• Stylopharyngeus Muscle (Musculus Stylopharyngeus).
• Palatopharyngeus Muscle (Musculus Palatopharyngeus).
• Salpingopharyngeus Muscle (Musculus Salpingopharyngeus).

7. Clinical Relevance:

• Pharyngeal Tonsil Enlargement (Adenoid Hypertrophy): Can obstruct nasal airflow and cause sleep apnea.
• Auditory Tube Dysfunction: Leads to middle ear infections (otitis media).
• Piriform Recess: Common site where food or foreign objects get lodged.

8. Sources:

• Memorix Anatomy, 2nd Edition by Hudák Radovan, Kachlík David, and Volný Ondřej.
• Biorender.
• University notes and lectures.

Transcript

Introduction
0:03
What’s up.
0:04
Meditay here, and in this video, we’re gonna go through the anatomy of the Pharynx.
0:09
So in the last video, we went through the anatomy of the Oral Cavity.
0:12
Now the step after the oral cavity is the Pharynx, as you see here.
0:17
So in this video, we’re first going to look at the parts of the Pharynx.
0:20
So we’re gonna go detailed into the anatomical structures associated with the Nasopharynx,
0:25
the Oropharynx, and the Laryngopharynx.
0:28
After that, we’ll cut the Pharynx and look at the layers of the pharyngeal wall.
0:33
And then we’re gonna go through the muscles that act on the Pharynx.
Parts of the Pharynx
0:37
Now, let’s start by holding the Pharynx and pulling it out.
0:41
You’ll see a kind of look like this as far as my anatomy program goes, at least.
0:46
Now the Pharynx is about 12 to 15 cm long, and it consists of three parts, as you see
0:51
here.
0:52
If we look at it anteriorly, you’ll see what the three parts are connected to.
0:56
The upper one is connected to the nasal cavity; we call it the Nasopharynx, or Pars nasalis
1:02
in Latin.
1:03
The middle part is associated with the oral cavity, so we call this one the Oropharynx.
1:08
The lower part is associated with the Larynx, so we call this Laryngopharynx.
1:13
Now, let’s change the scheme to a lateral view of the Pharynx to get a better overview.
1:18
We still have the Nasopharynx, Oropharynx, and Laryngopharynx here.
1:22
Now.
1:23
In terms of the digestive pathway, the Pharynx will continue downwards as the Oesophagus.
1:28
You can think of the Pharynx as a control point for breathing and swallowing, so the
1:33
Oesophagus is usually closed off when you’re breathing, as you see here.
1:37
But when you swallow, the soft palate blocks for the Nasopharynx so the food doesn’t end
1:42
up in your nasal cavity.
1:43
The Larynx gets blocked by the epiglottis, and the tongue pushes the food further down
1:49
by going up to the palate.
1:50
So that should give you a little overview of the Pharynx.
Nasopharynx
1:54
Let’s expand on that now y going through all structures associated with the Nasopharynx.
2:00
The Nasopharynx corresponds to the level of 1st to 2nd cervical vertebrae and is attached
2:06
to the base of the skull.
2:07
The attachment points between the Pharynx and the skull base are called Fornix Pharyngis,
2:12
or translated as the vault of the Pharynx.
2:15
The vault of Pharynx is where the mucosa, which is the wet surface in the Pharynx, is
2:20
firmly attached to specific regions on the base of the skull.
2:25
And to understand these attachment points, let’s look at this model right here and look
2:29
at it from this perspective.
2:31
And zoom in a little bit.
2:33
Now we’ll be able to see the attachment points of the Fornix Pharyngis.
2:37
Now just for orientation sake, here is the nasal cavity, and here’s the oral cavity.
2:41
SO, this blue line is the attachment points of the Pharynx, but there are some important
2:47
landmarks that should be noted when talking about the Vault of Pharynx, and they’re highlighted
2:52
here.
2:53
We have the Pharyngeal tubercule of the occipital bone, which is at the basal part of the occipital
2:57
bone.
2:58
The next attachment point is where the occipital bone and the petrous part of the temporal
3:03
bone fuse: the Petro-occipital fissures.
3:07
It also attaches to the inferior border of the Petrous part of the temporal bone.
3:13
And it attaches to the medial lamina of the pterygoid process.
3:17
So the Pharynx attached to these structures and forms the vault of Pharynx.
3:22
Alright, Now the Pharynx and the nasal cavity are connected, but there’s a strict border
3:28
between those two that you use as a landmark to separate the Pharynx from the nasal cavity,
3:34
And this border is called Choanae (or the internal nose).
3:38
That’s usually the border between the nasal cavity and the Pharynx.
3:41
Now another structure you find in the Nasopharynx is the auditory tube.
3:46
And that’s a tube that connects the middle ear to the Pharynx.
3:50
So let’s look a little bit into that.
3:52
SO here you see the eustachian tube or the auditory tube; it’s a synonym.
3:56
And it’s connected to the middle ear.
3:57
So we have the Outer ear, the middle ear, and the inner ear.
3:59
And in the middle ear, that’s where you’ll find the ossicles, which are called malleus,
4:04
incus, and stapes, and this is the tympanic membrane.
4:08
So the auditory tube connects the Nasopharynx to the middle ear.
4:12
Now, Why do you need the auditory tube?
4:14
Well, as you’re listening to my voice through this video, your eardrum or tympanic membrane
4:20
will vibrate in a specific manner.
4:22
This vibration will then be converted into words through the whole auditory pathway,
4:28
based on the vibration of the tympanic membrane.
4:31
And the tympanic membrane can vibrate because the pressure difference is stabilized.
4:36
And you see why it’s stabilized; the auditory tube is the only way the middle ear can regulate
4:41
its pressure.
4:43
At rest, the auditory tube is always closed, completely closed.
4:47
But remember, in our last video, we looked at the swallowing process and all the muscles
4:51
attached to the auditory tube?
4:54
If you now try to swallow, the auditory tube opens, and now you’ll feel a slight pressure
5:00
relief in the middle ear.
5:01
And that’s because the auditory tube opens up to relieve the pressure.
5:05
When you get in a plane, and you take off, or as you’re landing, and the cabin pressure
5:09
changes, you can feel that pressure change in the air, can’t you?
5:13
When you drive up and down mountains and hills, you feel that pressure change as well.
5:17
And what you’re feeling is the difference in pressure between the tympanic cavity in
5:22
here to the air pressure out here.
5:25
The usual mechanism is that an increase in pressure in the middle ear will push the tympanic
5:30
membrane outwards, decrease the pressure, and the tympanic membrane will be sucked in,
5:35
as you see here.
5:37
What can happen is that sometimes, this auditory tube gets stuck flat due to the pressure change.
5:42
Now, what do you do to get rid of that sensation?
5:45
Well, you swallow, you swallow, and then you feel a slight pop in the ear; that’s when
5:50
you know the eustation tube has opened again and relieved you from that pressure.
5:54
So that’s one function of the eustachian tube, equalizing the pressure.
5:59
Another thing is if you have a middle ear infection, and a lot of pus starts to build
6:03
up here.
6:04
The auditory tube can drain all that pus into the Pharynx to aid in clearing out that infection.
6:11
If the infections produce many symptoms, you can give some broad-spectrum antibiotics to
6:15
help out as well, like amoxicillin with clavulanic acid.
6:18
But we’re doing anatomy now, so the two main functions of the auditory tube are equalizing
6:23
the pressure when swallowing and draining the middle ear to protect from pathogens.
6:27
Alright, so that’s the tuba auditiva.
6:30
The point where the auditory tube opens into the Pharynx is called ostium pharyngeum tubae
6:37
auditivae, where ostium means opening in Latin.
6:40
Here, you’ll have cartilage protruding above the opening of the auditory tube called torus
6:47
tubarius, or cushion of the auditory canal.
6:49
As well as a small groove behind the auditory tube called the pharyngeal recess.
6:55
Now, we do have tonsils here as well in the Nasopharynx.
6:59
There’s the pharyngeal tonsil up here, or also called the adenoids.
7:03
Which can sometimes be inflamed and enlarged and block the auditory tube.
7:09
And another tonsil back here called the tubal tonsils.
7:12
And it’s called tubal tonsil because it’s behind the auditory tube.
7:17
So that was all for the anatomy of the Nasopharynx.
Oropharynx
7:21
Next is the Oropharynx, which is situated at the level of the third/fourth cervical
7:25
vertebrae.
7:26
The Oropharynx is bordered by the soft palate and the epiglottis, as you see here.
7:31
And It’s connected with the Oral cavity through something called isthmus faucium, or the oropharyngeal
7:37
isthmus, which is an opening at the back of the mouth into the throat.
7:41
Aaand, that is the Oropharynx; not much to talk about this one.
Laryngopharynx
7:45
Next, we have the Laryngopharynx, which is at the level of the 5th to 6th cervical vertebrae.
7:51
The Laryngopharynx is, as we saw earlier, going to continue into the Larynx.
7:57
So whenever you swallow, the epiglottis here will close the Laryngopharynx so the food
8:02
can enter the Esophagus and then down to your stomach instead of down into the lungs.
8:05
So these two openings are called the laryngeal inlet and the opening of the Oesophagus.
8:11
Alright, so if we look at the Larynx posteriorly, we can see the Nasopharynx up here, Oropharynx
8:17
here, and then we have the Laryngopharynx down here.
8:21
Now there’s one more anatomical landmark here on the Laryngopharynx, called the piriform
8:26
fossa which is located on either side of the Laryngopharynx.
8:30
The piriform fossa is a depression on either side of the Laryngopharynx.
8:34
So that was all the parts of the Larynx.
Layers of Pharyngeal Wall
8:36
Now, let’s go through the layers of the pharyngeal wall.
8:40
So if you look at the Pharynx again and cut it right about here, look from this perspective.
8:45
You’ll see that you have four layers.
8:47
The first one is the tunica mucosa, which lines the inner layer of the Pharyngeal cavity.
8:53
The mucosal layer is lined by epithelial tissue, and different regions are lined by a different
9:00
type of epithelium.
9:01
So if we take a small section of the Nasopharynx, you’ll see that it’s lined by respiratory
9:06
epithelium, which consists of pseudostratified epithelium with cilia, as well as goblet cells
9:11
between them.
9:12
While the rest of the Pharynx has to endure the pressure of food coming through the mouth,
9:18
so it’s lined by stratified squamous non-keratinized epithelia for protection.
9:22
So that is the first layer.
9:24
The next layer is the tela submucosa, containing primarily Connective Tissue, Blood Vessels
9:30
and Lymph Vessels, and Glands.
9:32
So that was this Layer The next layer Is a muscle layer Called tunica
9:37
muscularis, consisting mainly of Two types of muscle fibers.
9:41
The inner muscle fibers are arranged circularly, and the outer ones are arranged longitudinally.
9:48
And here you See Why We Call Them Circular and longitudinal.
9:51
You can see that the internal part looks circular while the outer part looks longitudinal.
9:58
And that is to aid the pharyngeal peristalsis.
10:00
Peristalsis is the controlled synchronized contraction to help with the movement of the
10:06
content either in or out.
10:08
So that is this Layer.
10:10
The last layer is the Tunica Adventitia, which is a tough layer of collagen fibers that cover
10:16
the Pharynx from the outside.
Muscles of the Pharynx
10:18
So that was the pharyngeal wall.
10:20
The last thing we’re gonna look at is the external muscles of the Pharynx!
10:25
We divide the muscles of the Pharynx into the Pharyngeal Constrictors and the Pharyngeal
10:30
elevators.
10:31
Both of them Consisting of Three Muscles Each.
10:33
And you know only by looking at their names constrictors and elevators, you can kind of
10:38
already get a hinch of their function.
10:40
Alright, so let’s start with the constrictors first.
10:43
So here you see the Pharynx and the skull.
10:44
And here you see all the three Constrictors muscles.
10:48
You have the first one, which is called the superior pharyngeal constrictor.
10:52
If we zoom in a little bit, you’ll see that it originates from the pterygoid process,
10:57
the pterygomandibular raphe.
10:59
And it’s also going to originate from the mylohyoid line of the mandible.
11:03
Then it’s going to insert at the Pharyngeal raphe as you see here.
11:07
The whole white line right here is the Pharyngeal raphe.
11:12
So that is this muscle.
11:14
The next muscle is the Medial pharyngeal constrictor highlighted right here.
11:18
It’s going to originate from the hyoid bone and insert at the raphe pharyngis.
11:23
And the last one is the inferior pharyngeal constrictor, highlighted right here.
11:26
This one is pretty interesting because this one will originate from the thyroid cartilage
11:30
and the cricoid cartilage; those are the cartilages of the Larynx, the voicebox.
11:34
And then, they will insert at the pharyngeal raphe as well.
11:37
So the constrictors of the Pharynx are very easy to remember because they all have the
11:42
same name.
11:43
There are the superior medial and inferior pharyngeal constrictors.
11:47
They all have the same insertion point, which is the pharyngeal raphe.
11:51
And they all have the same function, which is constricting the Pharynx as you swallow
11:55
to aid the peristalsis, which is the movement of the pharyngeal wall to move the content
12:01
downwards.
12:02
Alright So now the next group of muscles is the Pharyngeal
12:05
Elevators.
12:06
And remember, the constrictors will constrict the Pharynx, and the elevators will make sure
12:12
it elevated the Pharynx when you swallow.
12:14
The first one is the stylopharyngeus muscle.
12:18
This one will originate from the styloid process and insert at the lateral wall of the Pharynx.
12:24
Again remember, since it originates from up here and inserts down here, that means when
12:29
these muscle fibers contract, they’re going to elevate the Pharynx.
12:34
The next one is the palatopharyngeus muscle.
12:37
So looking at this name, it originated at the soft palate and inserts at the Pharynx.
12:43
Or, to be specific, it originates at the aponeurosis of the soft palate and inserts at the lateral
12:50
wall of the Pharynx.
12:51
And finally, the last muscle of the elevators is the salpingopharyngeus muscle.
12:56
It’ll originate from the walls of the auditory tube and insert at the palatopharyngeus muscle
13:05
fibers.
13:06
So when you swallow, it’s also going to help open the auditory tube because remember, the
13:09
auditory tube is closed normally and only open when you swallow.
13:10
So that was the anatomy of the Pharynx.
13:11
The next video is going to be about the Esophagus.