Muscles of the Palate and Pharynx
While these muscles cover a large area and they grouped together as they are important in swallowing. They do not make movements that are readily visible as they are mostly involved in swallowing and swallowing is best accomplished with the mouth closed. Many of them are used in the doctor’s office when one says, “Ah” so they can look at your posterior pharyngeal wall. They have a variety of nerves that innervate them all of which have to be coordinated to swallow effectively.
Tensor Veli Palatini
This paired muscle, the tensor veli palatini originates over an area that includes the medial pterygoid plate of the sphenoid, the spine of the sphenoid and importantly on the lateral surface of the cartilage that forms the eustachian (auditory) tube. It inserts on a band of connective tissue that runs along the posterior edge of the hard palate. When contracted it has two effects: it tenses the palatal aponeurosis which anchors other muscles, so it acts as a synergist to their actions and importantly also helps open the eustachian tube to equalize the pressure in the middle ear. It is activated when swallowing which is why swallowing helps relieve the pressure buildup in the ear when changing altitude especially noticeable when flying. It is innervated by a branch of the nerve to the medial pterygoid which one should remember is a muscle of mastication and therefore originates from the third division of the trigeminal nerve (cranial nerve V3 – cranial nerve V - 3rd division). It is the only palatal muscle not innervated by the vagus (cranial nerve X).
Levator Veli Palatini
Another small paired muscle found in the soft palate is the levator veli palatini. It originates on the petrous portion of the temporal bone and like the tensor veli palatini also from the eustachian tube though on the medial side rather than the lateral side. Its insertion is on the palatine aponeurosis. When contracted it helps open the eustachian tube but as indicated by its name it elevates the palate also. It is innervated by nerves that originate in the vagus nerve (cranial nerve X).
The left and right palatopharygeus muscles actually underlie a structure you can see in your own mouth, if your palatine tonsils are either missing or small enough, as it lies directly behind the palatine tonsil on both sides of the mouth. These bilateral structures are referred to as the posterior tonsillar pillars. They are formed as the muscle goes from its origin in the palatal aponeurosis and adjacent hard palate and its insertion in the thyroid cartilage. It will elevate the thyroid cartilage when contracted which by extension raises the larynx and pharynx. It, like the levator veli palatini, is innervated by fibers from the vagus nerve.
The palatoglossus muscles form the anterior tonsillar pillars which lie anterior to the palatine tonsils so are easily visualized by looking in a properly illuminated throat. As they run from their origin in the palatine aponeurosis to the insertion in the tongue it forms a curtain of tissue which as a continuation from the posterior border of the soft palate defines the posterior extent of the oral cavity. This muscle acts to lift the tongue towards the palate while simultaneously lowering the soft palate towards the tongue. This is important to help force food into the pharynx. Because it is also a tongue muscle it is often grouped with them also but here to lessen redundancy we will assume you will remember that and we will not cover it again. Like all of the other palatal muscles except the tensor veli palatini it is innervated by branches of the vagus nerve found in the pharyngeal plexus. One reason to put it here is that its innervation follows palatal patterns while all the other tongue muscles in that group are innervated by the hypoglossal nerve(cranial nerve XII).
Muscle of the Uvula
Despite the way the name sounds the muscle of the uvula is a pair of muscles that originate in the posterior hard palate and insert in the palatine aponeurosis and the soft tissue of the uvula. The uvula can be shortened by contracting the pair or deviated to one side or the other by contracting just one of them. It is innervated by the pharyngeal plexus of nerves.
Superior Pharyngeal Constrictor
The superior pharyngeal constrictor muscle is broad muscle with a long origin that runs from the mandible inferiorly up the pterygomandibular raphe to the pterygoid hamulus of the sphenoid bone. The raphe is visible as a tissue fold in the mouth that runs from the distal part of the maxillary tuberosity to the mandibular mylohyoid ridge. It inserts into a raphe posteriorly that connects the two pharyngeal constrictors to each other known as the pharyngeal raphe. This band of tissue runs in the posterior wall of the pharynx. As the muscle contracts then it constricts the pharynx as the muscle pulls against itself. This acts to force food down the pharynx. It also innervated by the pharyngeal plexus.
Middle Pharyngeal Constrictor
The middle pharyngeal constrictor muscle is also a broad muscle with an origin that extends from the hyoid bone and then up the stylohyoid ligament that extends from the hyoid bone to the styloid process of the temporal bone. It inserts into the pharyngeal raphe inferior to the superior pharyngeal constrictor. Like the superior constrictor it acts to force food down the pharynx and is innervated by the pharyngeal plexus.
Inferior Pharyngeal Constrictor
The inferior constrictor muscle, as expected by its name is the most inferior of the three constrictors. It originates as separate bellies on the cricoid and thyroid cartilages of the larynx. Like the other two constrictors it also inserts into the pharyngeal raphe and constricts to collapse the pharynx but unlike the other two it is generally contracted to keep air from getting into the esophagus during breathing. It is this muscle that kids learn to relax to be able to burp at will to impress their friends. It is also used by post-laryngectomy patients to enable them to speak. Given good enough control they use them as substitute for surgically removed vocal folds. While both bellies are innervated by the vagus nerve (cranial nerve X) not all the fibers come from the pharyngeal plexus as the cricoid part often has branches feeding it from laryngeal branches of the vagus.
The stylopharyngeus muscle originates at the styloid process of the temporal bone but the insertion is not so clear cut as it merges into various muscles as it comes into proximity with them. Some fibers end up joining the superior and middle pharyngeal constrictors but the majority join with the salpingopharyngeus (Figure 3) muscle discussed below and insert into the thyroid cartilage. The position of the origin relative to the insertion means that it will elevate the larynx when contracted. This muscle is the exception in the pharyngeal muscles and is innervated by branches of the glossopharyngeal nerve (cranial nerve IX).
The salpingopharyngeus muscle originates at the base of the eustachian tube. As mentioned in the discussion of the stylopharyngeus muscle the fibers of the two muscles merge and insert into the thyroid cartilage. Both ends of this muscle are attached to movable tissue so when it contracts it opens the auditory tube orifice in the pharynx and along with the two veli palatini muscles allows the middle ear pressure to equalize with the ambient air pressure while also elevating the larynx. It is, like all but one of the pharyngeal muscles, innervated by the vagus nerve through the pharyngeal plexus.