The constrictor pharyngis inferior muscle is the lower pharyngeal lacing muscle and contributes to speech and swallowing. Both of these tasks can be disrupted if the constrictor pharyngis inferior muscle fails, cramps, or is otherwise impaired. This is the case, for example, in nerve palsy or in the setting of a peritonsillar abscess.
What is the inferior constrictor pharyngis muscle?
The constrictor pharyngis inferior muscle is the lower of the three pharyngeal constrictors. The other two muscles in this group are the superior constrictor pharyngis muscle and the medius constrictor pharyngis muscle. Together, the pharyngeal constrictors carry food or fluid to the esophagus during the pharyngeal transport phase. During pregnancy, the constrictor pharyngis inferior muscle develops from the sixth gill arch of the embryo. This gill arch also contains the attachments for the laryngeal muscles (musculi laryngis), parts of the larynx, and blood vessels. Since in the embryo the fourth and sixth gill arches merge after only a short time, there is a closer relationship, both spatially and functionally, between the musculus constrictor pharyngis medius and inferior than between these two muscles and the musculus constrictor pharyngis superior. The latter is located at the top of the pharynx and, together with the soft palate elevator (Musculus levator veli palatini) and the soft palate tensor (Musculus tensor veli palatini), closes the nose during swallowing.
Anatomy and structure
The inferior pharyngis constrictor muscle combines two parts: the pars thyropharyngea and the pars cricopharyngea. Both attach to the pharyngeal suture, which anatomy also calls the raphe pharyngis. It is located on the back wall of the pharynx and is partially visible from the outside through the pharyngeal mucosa. The other pharyngeal lacing muscles also attach to the pharyngeal suture. The two parts of the inferior constrictor pharyngis muscle have different origins on the larynx. One of the laryngeal cartilages is the annular cartilago cricoidea, which has grooves. At one such notch – the linea obliqua – the pars cricoidea of the constrictor pharyngis inferior muscle originates. The pars thyroidea, on the other hand, originates from the cartilago thyroidea, also known as the thyroid cartilage or thyroid, which provides support for the pars thyroidea at its outer edge. Overall, the constrictor pharyngis inferior muscle presents a fan-shaped appearance. It occurs once on each side of the body and belongs to the striated musculature. Nerve fibers from the ninth and tenth [[cranial nerves (glossopharyngeal and vagus nerves) control the activity of the inferior pharyngeal constrictor, which is joined by the esophagus.
Function and tasks
The tasks of the inferior constrictor pharyngis muscle include two functional areas. On the one hand, it plays a role in speech, and on the other hand, it contributes to swallowing. The constrictor pharyngis inferior muscle influences the position of the larynx via the cartilage where its origin is located. At this point, the vocalis muscle and the cricothyroid muscle also act on the vocal folds, which medicine also refers to as the internus and externus. They belong to the laryngeal muscles. In the swallowing act, the constrictor pharyngis inferior muscle is active during the pharyngeal transport phase. Prior to this, the mouth crushes the food in the oral preparatory phase and transports the food pulp or liquid to the pharynx in the oral transport phase. The subsequent pharyngeal transport phase consists of a complex interaction of different muscle groups. The soft palate tensor (Musculus tensor veli palatini), the soft palate elevator (Musculus levator veli palatini) and the superior pharyngeal constrictor (Musculus constrictor pharyngis superior) seal off the nasopharynx from penetrating food. With the help of the suprahyoidal and infrahyoidal muscles, the tongue pushes the contents of the mouth further back into the pharynx. The constrictor pharyngis medius muscle is responsible for transport in the oral pharynx (mesopharynx), and the constrictor pharyngis inferior muscle is responsible for further transport of food in the laryngeal pharynx (hypopharynx). The pharyngeal transport phase is followed by the esophageal transport phase, in which the tunica muscularis of the esophagus pushes the morsel to the stomach.
Diseases
Impairments of the inferior constrictor pharyngis muscle can interfere with speech and swallowing. Paralysis of the ninth and tenth cranial nerves, which innervate the inferior pharyngeal nerve, is a possible cause of such disorders. Nerve failure also affects other parts of the speech and swallowing muscles. The fibers of the glossopharyngeal and vagus nerves pass over the pharyngeal plexus. The plexus, like the upper portions of the cranial nerves, can suffer from inflammation, tumors, hemorrhage, poisoning, and injury. Less commonly, radiation from breast carcinoma causes unintended damage to the pharyngeal plexus. Events such as strokes or epileptic seizures, as well as neurodegenerative diseases, can also affect the cranial nerves and their core areas in the brain. The extent and duration of the lesion vary greatly from case to case and depend not only on the underlying cause but also on individual factors. In tonsillitis, in some cases the infection spreads to other tissues. This may also affect the upper tonsillar fossa (supratonsillaris), which is associated with the pharyngeal cords, and result in an abscess. Medicine also refers to such pus formation as a peritonsillar abscess. This typically causes pain when swallowing, which may radiate to the ear, and leads to swelling in the affected area. If the chewing muscles also become inflamed and cramped, those affected also suffer from lockjaw (ankylostoma): they can no longer open their mouths without hindrance. Other symptoms of peritonsillar abscess include difficulty speaking and general signs of illness such as fever, chills and malaise.
