Soft palate

Structure

The soft palate is suspended from the posterior margin of the hard palate, with the border between the two being easily palpable. It is distinguished from the hard palate by having a darker red color with a yellowish tone.

Lying between the oral and nasal cavities, the soft palate features the oral and nasal surfaces.

• The oral surface is covered by the non-keratinized stratified squamous epithelium with secretory salivary glands. The mucosa contains a few taste buds and features a longitudinal raphe in the midline. On each side of the raphe is an opening of the mucous palatine glands, called the palatine fovea. The oral surface also forms the roof of the oropharyngeal isthmus, an area connecting the pharynx and oral cavity.
• The nasal surface is lined by the simple ciliated columnar epithelium (respiratory epithelium) and it is continuous with the floor of the nasal cavity.

The four borders of the soft palate are the anterosuperior, two lateral, and an inferoposterior border.

• The anterosuperior border is attached to the hard palate via the palatine aponeurosis.
• The lateral borders feature two arches; palatoglossal (anteriorly) and palatopharyngeal (posteriorly). Via these arches, the lateral borders of the soft palate are continuous with the tongue and the lateral wall of the pharynx, respectively.
• The posteroinferior border of the soft palate is free and faces towards the oropharynx. It features a conical expansion in the midline called the uvula that projects into the oral cavity.

The core of the soft palate consists of the palatine aponeurosis and 5 muscles of the soft palate. The palatine aponeurosis is an expansion of the tendon of the tensor veli palatini muscle and it comprises the anterior one-third of the soft palate. The aponeurosis is thick anteriorly and serves to attach the soft palate to the bony framework of the hard palate. It becomes thinner posteriorly, enclosing the musculus uvulae and blending with the remaining muscles of the soft palate. The muscles of the soft palate comprise the posterior two-thirds of its core. Namely, these muscles are the musculus uvulae, tensor veli palatini, levator veli palatini, palatopharyngeus and palatoglossus muscles.

Palatoglossal and palatopharyngeal arches

The palatoglossal and palatopharyngeal arches are the two mucosal folds that extend inferiorly from each lateral border of the soft palate.

• The palatoglossal arch is located anteriorly. It contains the palatoglossus muscle and connects the soft palate with the root of the tongue.
• The palatopharyngeal arch is found posteriorly and it contains the palatopharyngeus muscle. It joins the soft palate with the wall of the pharynx.

These two arches together are called the pillars of fauces, because they bound the space called the fauces, or simply the throat. The roof of the fauces is the oral surface of the soft palate, while the floor is the root of the tongue. The posterior, constricted part of the fauces is called the isthmus of the fauces and it is a gate between the oral cavity and oropharynx. The space between the tongue and palatoglossal and palatopharyngeal arches is called the tonsillar fossa (sinus), and it is where the palatine tonsils are located.

Muscles of the soft palate

The five palatine muscles originate either from the base of the skull or the pharyngeal walls and reach the soft palate by travelling in various directions. They all insert to the palatine aponeurosis, either directly, or indirectly by blending with each other.

The muscles of the soft palate produce its movements which are essential for the processes of swallowing and speech;

• The palatopharyngeus and tensor veli palatini muscles produce the tension of the soft palate during swallowing. This enables the tongue to press against the soft palate and push the food towards the oropharynx.
• The elevation of the soft palate is produced by the levator veli palatini muscle. This movement brings the soft palate into contact with the posterior pharyngeal wall, closing the isthmus of the pharynx. This closes the communication with the nasal cavity and prevents the food from passing into it.
• The depression of the soft palate is caused by the palatoglossus muscle. This brings its oral surface in contact with the root of the tongue, closes the isthmus of the fauces and initiates the act of swallowing. This also results in exhaling through the nose even if the mouth is open, and prevents the contents from the oral cavity from passing into the pharynx.

For more information about the soft palate and its corresponding muscles, take a look below:

 Innervation and blood supply

The anterior part of the soft palate is sensory innervated by the lesser palatine nerve, which is a branch of the maxillary division of the trigeminal nerve (CN V2). The posterior part, however, is sensory innervated by the pharyngeal branches of the glossopharyngeal nerve (CN IX) and by the plexus around the pharyngeal tonsils formed by the branches of the pharyngeal and lesser palatine nerves.

The motor innervation for the muscles of the soft palate comes from the pharyngeal plexus derived from the vagus nerve (CN X). The only exception is the tensor veli palatini muscle which is supplied by the medial pterygoid nerve, a branch of the mandibular division of the trigeminal nerve.

The taste buds of the soft palate are innervated by the greater petrosal nerve, a branch of the facial nerve (CN VII). The mucous glands of the soft palate are parasympathetically innervated by the postganglionic fibers from the otic ganglion. They reach the soft palate via the lesser petrosal branch of glossopharyngeal nerve.

The blood supply for the soft palate comes from the ascending palatine artery, a branch of facial artery. The venous drainage is conducted via the pterygoid venous plexus.

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Function

The function of the soft palate is to facilitate speech, breathing and swallowing by making sure that the proper communication channels between the oral, pharyngeal and nasal cavities are open or closed during each of these processes.

• During swallowing, the soft palate tenses and helps in pushing the food down the digestive tract. Immediately after this, the soft palate elevates and closes the way to the nasal cavity, thus making sure that no food can pass back to the nasal airways.
• During nasal breathing, the soft palate depresses and gets in touch with the root of the tongue, making sure that the food doesn’t pass to the oropharynx and gets in the way to the stream of exhaled air.
• When it comes to speech, the soft palate tenses and elevates. In this case, the back of the tongue presses against the soft palate in order to produce the velar sounds, which in English language are the [k], [g] and [ŋ]. It is important that the movement of the soft palate closes the communication with the nasal cavity. Otherwise, some air escapes from the oral cavity through the nose, making the speech sound nasal.

The defects in the development of the palate are common, and can result in a condition called the cleft lip or a cleft palate. After birth, these children can have serious problems with feeding, speaking and infections. 

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