ISTHMUS OF THE FAUCES: ANATOMY, FUNCTIONS, DISEASES - ANATOMY AND PHYSIOLOGY - 2024

The isthmus of the fauces or oropharyngeal isthmus is the narrowest and posterior portion of the oral cavity, which is irregularly shaped and establishes communication between the oral cavity and the oropharynx.

It is also called the “posterior orifice of the mouth”, some bibliographies resemble its shape with that of an “M” and it is circumscribed by the root of the tongue below, the palatoglossal arches on both sides and the free edge of the soft palate with the uvula above.

It is limited by muscle formations that form the muscular apparatus of the soft palate (soft palate) and ensure its mobility, of which four are even and one is odd.

It is characterized by containing Waldeyer's ring, a set of structures composed of lymphatic tissue whose main function is to defend the air and digestive tracts by activating the immune response in the presence of pathogens in the area.

Of the structures that make up Waldeyer's ring, the palatine tonsils are those that are in direct relationship with the isthmus of the fauces.

Anatomy

Tensor veli palate muscle

Also called the external peristaphylline muscle, it originates from the scaphoid fossa, at the base of the pterygoid process of the sphenoid bone, and on the anterolateral aspect of the cartilage of the auditory Eustachian tube.

From there it is inserted through a fan-shaped tendon in the anteromedial part of the palatal aponeurosis, that is, its termination is submucosal.

Its action is to laterally tighten the soft palate, which produces the opening of the isthmus of the fauces in swallowing and creating a septum between the oropharynx and the nasopharynx to oppose the rise of the food bolus towards the nasopharynx.

Levator soft palate muscle:

It is also called the internal peristaphylline muscle, it has its origin in the petrous portion of the temporal bone and in the medial aspect of the cartilage of the auditory tube.

It is inserted with a fan-shaped tendon above the superior aspect of the soft palate aponeurosis.

Its action is to raise the soft palate and dilate the Eustachian tube. In this way, it favors the opening of the isthmus of the jaws in conjunction with the tensor vellus muscle, allowing swallowing.

Palatoglossus muscle

It is also called the glossostafillin muscle. It has its origin through two fascicles at the root of the language; both fascicles unite and expand in the soft palate, mixing with its counterpart on the opposite side.

Its action is based on the elevation of the root of the tongue, the soft palate descends and narrows the isthmus of the jaws like a sphincter, which allows chewing, sucking, as well as the last time of swallowing that it projects. the food bolus into the esophagus.

Palatopharyngeal muscle

It is also called the pharyngostafillin muscle. It originates from the soft palate, by fibers that are found posterior to the middle raphe and the uvula muscle. Its fibers intersect with those of the levator vellus muscle.

It inserts into the lower part of the cartilage of the auditory tube and into the hook of the pterygoid process. Both attachments join and form a single muscle belly, which penetrates the palatopharyngeal arch and ends in a pharyngeal fascicle and a thyroid fascicle.

By its action, like that of the palatoglossus muscle, it narrows the isthmus of the jaws, bringing the arches closer together and isolates the lower part of the oropharynx from the nasopharynx.

Uvula muscle

It is also called the palatostaphylline muscle. It originates from the posterior nasal spine, ends at the apex of the palatal uvula attached to the posterior aspect of the soft palate aponeurosis. By its action it raises the uvula.

Features

The main function of the isthmus of the fauces is to act as a regulator in various actions of the oropharynx.

Its opening prevents the food bolus from ascending to the nasopharynx during the swallowing process, while its contraction or closure allows chewing and sucking, as well as the impulse in the last stage of swallowing to descend the food bolus into the esophagus.

When the isthmus of the fauces is opened as a consequence of a contraction of the levator and tensor muscles of the soft palate, the free circulation of air from the nasopharynx to the middle ear is favored, helping to regulate the air pressures between them.

That is why swallowing movements restore balance in the tympanic cavity when it has been disturbed.

For example, in the sensation of "blocked ear" when ascending or descending from great heights due to pressure changes, with the action of "swallowing" the isthmus of the jaws is opened and control is reestablished in the pressures between the nasopharynx and middle ear, bringing the "uncovered ear" as a consequence.

Related diseases

The pathologies related to the isthmus of the fauces are mainly caused by the structures contained in the limit that the isthmus indicates, being of special importance the palatine tonsils.

The isthmus itself does not represent a described pathology. In some felines, the inflammation of the posterior gingival mucosa is called "faucitis", commonly called the fauces in mammals. However, the term is not used in the area of ​​human stomatology.

The hyperplasia of the palatine tonsils represents the most frequent pathology related to the isthmus of the fauces. They cause dysphagia, swallowing disorders, velopalatine mobility decreases and can cause nocturnal snoring.

Regarding benign tumor pathology present in the oropharynx, there is a fibroma that appears in areas of friction due to chronic irritation phenomena and whose treatment is purely surgical.

On the other hand, papilloma is the most frequent benign tumor, secondary to infection by the Human Papilloma Virus. It can become malignant although it is not frequent, and its resolution is in the same way clearly surgical.

References

1. The Ruiz Liard card. Human anatomy. 4th Edition. Volume 2. Editorial Médica Panamericana. Pages 1228-1232
2. CTO Manual of Medicine and Surgery. Otorhinolaryngology. 8th Edition- CTO Group. Editorial CTO.
3. Isthmus of the Maw. Abstracts Medicine. Recovered from: medicsummary.blogspot.pt
4. Dr. Gustavo Reales. Basic Clinical Knowledge. Basic Implantology Manual. Chapter 1. Page 4.
5. Salvador F. Magaró. Clinical manifestations of swallowing disorders. Separata 2006. Vol 14 N ° 1.