Pharynx: Definition, Structure, Function

• Pharynx functions as a passageway for food from the oral cavity to the oropharynx.
• Pharynx functions as a passageway for air from the nasal or oral cavity through the pharynx into the larynx and trachea.
• A valve, specifically the soft palate, prevents inhalation of food.
• Pharynx equalizes air pressure between the middle ear and atmosphere via the auditory tube.
• Pharynx functions in swallowing by moving the bolus toward the oesophagus.
• Pharynx functions in speech by altering the vocal tract shape to change resonance.
• Constriction of the vocal tract changes air flow, creating turbulence, which aids in speech.
• Pharynx serves a protective function.

Definition and Structure of the Pharynx

• The pharynx is approximately 12 cm long
• It is cone-shaped.
• It is a musculo-tendinous tube.
• The pharynx extends from the nasal cavities (pharyngeal tubercle of the occipital bone) to the vocal folds (cricoid cartilage at C6).
• The anterior opening of the nasopharynx is the choanae.
• The anterior opening of the oropharynx is the fauces.
• The anterior opening of the laryngopharynx is the aditus laryngis.
• The fauces is the region between the anterior faucial pillar (palatoglossal arch) and the posterior faucial pillar (palatopharyngeal arch).
• The palatine tonsil is within the fauces.
• The velum refers to the soft palate.

Layers of the Pharynx

• The pharynx consists of an inner mucous membrane.
• The middle layer is connective tissue, called the pharyngeal aponeurosis, with a dense CT sleeve.
• The pharyngeal aponeurosis is attached to the base of the skull, hyoid, and thyroid cartilage.
• The aponeurosis gives attachment to the pharyngeal muscles.
• It is strengthened posteriorly by a fibrous band known as the median raphe.
• The muscle layer contains external circular muscles.

Nasopharynx

• It is static in size and shape.
• It serves as a resonating chamber.
• It functions in respiration.
• It equalizes air pressure.

Oropharynx

• The oropharynx is dynamic.
• It has a mobile soft palate and tongue
• It functions in respiration and digestion
• It serves as a resonating chamber.
• Voiced fricatives are generally produced with a larger pharynx than voiceless fricatives at the same place of articulation.

Laryngopharynx

• The inferior border is aditus laryngis (entrance to the larynx) at C6.
• It modifies laryngeal tone and assists in digestion.
• Openings around the epiglottis reduce the risk of food entering the lungs.
• Valleculae is the spaces formed by the attachment of the tongue base to the epiglottis via the glossoepiglottic folds.
• The pyriform sinus is the recess between the aryepiglottic fold and thyroid cartilage.
• The pyriform sinus directs the bolus laterally away from the larynx toward the oesophagus.

Connective Tissue Definitions

• Aponeurosis a thin sheet of connective tissue that provides attachment for muscles.
• Raphe is the union of two lateral halves.
• Pharyngeal aponeurosis is between the mucous and muscular layers of pharynx
• It attaches to the occipital bone and is continuous laterally with the palatine aponeurosis.
• The pharyngeal raphe extends from the pharyngeal tubercle on the occiput to the posterior oesophagus.
• It is a narrow band of connective tissues at the posterior joining of the pharyngeal constrictor muscles.

Muscles of the Pharynx

• The external layer consists of 3 constrictors.
• Muscles are circular with fixed points.
• The Superior constrictor attaches the pharyngeal tubercle to the pharyngeal raphe
• The Middle constrictor attaches the hyoid to the pharyngeal raphe.
• The Inferior constrictor is divided into:
• Thyropharyngeus, which attaches the thyroid cartilage to the pharyngeal raphe
• Cricopharyngeus, which attaches the cricoid cartilage to the opening of the oesophagus.

Sequential Constriction

• The pharynx pushes the bolus down into the oesophagus in an involuntary phase of swallowing (second stage).
• Cricopharyngeus is generally contracted, acting as a sphincter.
• Pharyngealization is a secondary articulation, and simultaneous articulation at two places, where the pharynx or epiglottis is constricted during the articulation of sound.
• Pharyngealization does not appear in English

Internal Longitudinal Muscles

• Stylopharyngeus
• Palatopharyngeus
• Salpingopharyngeus
• The Stylopharyngeus attaches to the styloid process.
• It also attaches to the pharyngeal constrictor and post thyroid cartilage.
• Stylopharyngeus elevates and opens the pharynx.
• The Palatopharyngeus attachs to the anterior hard palate and midline soft palate
• It also attaches to the post margin thyroid.
• During Actions the Palatopharyngeus elevates the pharynx with raised soft palate, contraction narrows oropharynx, and the uvula prevents food from re-entering the mouth.
• Palatopharyngeus lowers the soft palate
• The Salpingopharyngeus attaches to the medial Eustachian tubes to the posterior thyroid region.

Actions of the Internal Longitudinal Muscles

• Salpingopharyngeus elevates lateral walls of pharynx
• It equalises pressure between the auditory canal and pharynx,
• Overall they elevate the pharynx as a whole, elevating the larynx
• The muscles change length of resonating column of air above the larynx
• Decreased length (via relatively elevated larynx) is associated with higher pitch
• Increased pharynx length is associated with lower pitch
• Increased lung volume exerts a greater downward pull on the larynx via the trachea, lengthening the pharynx and lowering pitch.
• Fine control of pitch occurs in the larynx via laryngeal muscles.

Hard Palate

• It consists of a hard palate and soft palate (velum).
• Separates nasal and oral cavities.
• It is formed by the palatine process of the maxilla and palatine bones.
• Two bones meet at the intermaxillary suture (or median palatine suture).
• Palatal vault (arch) has a height that affects acoustics and varies.
• It features rugae, ridges of mucous membrane, facilitating articulation.

Soft Palate Roles

• It is a flexible opening between the nasal cavity and the oral cavity.
• The soft palate is raised (elevated) to close the entrance to the nasal cavity during swallowing (preventing food from entering the nasopharynx) and during many speech sounds and blowing.
• the soft palate is lowered (depressed) to open the entrance to the nasal cavity during some speech sounds (sing , nigh) and breathing.
• Soft palate depression Palatoglossus is when the Anterior faucial pillar lifts tongue
• They also narrow the pharynx Palatopharyngeus Depresses soft palate.
• The Posterior faucial pillar narrows the pharynx
• Soft palate elevation Levator veli palatini raises and retracts soft palate.
• Soft palate elevation Tensor Veli Palatini hooks around hamulus, tenses the soft palate, and dilates the eustachian tube.
• Musculus uvulae has bunches that shortens with contraction
• Superior constrictorPulls the posterior pharyngeal wall forwards to meet the soft palate.

Velopharyngeal Closure

• The role of velopharyngeal closure is to vary the degree of acoustic coupling between the oral and nasal cavities.
• Velopharyngeal closure is necessary for the production of "oral stops" sounds - raising the soft palate to the posterior pharyngeal wall prevents air from exiting through the nasal cavity.
• Velopharyngeal closure impounds air pressure within the oral cavity for plosive consonants
• The speech sounds m/n/ng require a depressed soft palate
• Inadequate velopharyngeal closure leads to nasalised vowels and weak plosives.
• It's a continuous sphincter type of arrangement at the superior pharynx.
• The soft palate closes the 'roof' above this opening.

How Velopharyngeal Closure is Achieved

• It is achieved by palatal movement
• Elevate (LVP) and tense (TVP) soft palate
• anterior movement of posterior pharyngeal wall
• superior constrictor around C1
• Inward or medial movement of the lateral walls of the nasopharynx
• superior constrictor, buccinator and orbicularis oris

Motor Nerve Supply

• Muscles of the palate: All the muscles of the palate are supplied by Cranial nerve X (vagus) except for tensor veli palatini which is supplied by mandibular branch of trigeminal(Vmand).
• Muscles of pharynx: All the muscles of the pharynx are supplied by Cranial nerve X (vagus) except for stylopharyngeus which is supplied by Cranial nerve IX (glossopharyngeal).

Mastication and Deglutination

• It involves more than 30 muscles and nerves with actions that are both voluntary and involuntary.
• This is known as a complex process involving the integration of :
• facial actions (open lips to receive food then close to contain food in oral cavity)
• lingual actions(collecting food and bolus preparation)
• mandibular actions (jaw held closed while the tongue pushes the bolus back into the throat)
• velar actions (sealing off nasal cavity from food/fluid)
• pharyngeal actions(moving bolus down into oesophagus) muscle movements
• the airways need to be protected during swallowing (larynx adjustments)

Swallowing Phases

• The first phase is Oral preparatory - Bolus is formed.
• The second phase is Oral (1s) -food leaves oral cavity
• The third phase is Pharyngeal (1s) bolus traverses pharynx
• The fourth phase is Oesophageal (1s) bolus traverses pharynx
• Swallowing involves coordination with breathing processes.
• Breathing pauses briefly during swallowing to allow the bolus to pass through to the oesophagus

Oral Preparatory Stage

• Food is tasted and ground up - mastication muscles
• The soft is against the tongue base (palatoglossus) to allow nasal breathing and to keep the food in the oral cavity.
• The phases of chewing and formed into bolus - action of tongue and teeth
• Softening of bolus is completed via salivation
• A bolus is a small rounded mass of chewed food at the moment of swallowing.

Chewing Cycle

• Tongue presses the bolus against hard palate
• Tongue then pushes food onto the tooth surface
• The Jaw closes Food is therefore crushed.
• The Jaw opens and the tongue repositions the partially crushed food again onto the teeth for further breakdown
• Buccinator compresses the food that has shifted into the vestibule back over the molars during grinding, elevation, then the tongue elevates the muscles of the masster, temporalis, medial and lateral pterygoid
• The soft palate is lowered using the palatoglossus, and palatopharyngeus to allow soaft palate to lowered.

Tongue Action

• The tongue deviates the tip (superior and inferior longitudinals)
• The tongue cups shape with the vertical, and genioglossus muscles
• Elevation of the tongue via the styloglossus, palatoglossus.
• Closed lips (orbicularis oris), food kept in between teeth (buccinator, risorius)
• Bolus is crushed pressed to hard palate, floor of mouth raised and midline depression of tongue obliterated, this is completed by the mylohyoid.
• Bolus maintained in midline because tongue is formed into a V-shaped trough ie. elevated sides+ centre drawn down using the styloglossus, palatoglossus, hyoglossus, genioglossus, vertical intrinsics
• Fluid such as that drawn sucked in via a straw requires:-
• Lips to seals seal around straw
• Oral cavity to be sealed posteriorly by tongue and soft palate.
• Cheeks and mouth floor braced
• Mandible lowered and tongue depressed and retracted
• Subatmospheric pressure is generated within the oral cavity

Oral Transport Stage

• The oral phase of swallowing transport occurs over 0.5-1 seconds
• Mastication ceases and the jaw closes
• Mandible elevators include: masseter, temporalis, Med pt
• The Bolus is passed into oropharynx by Anterior Elevating muscles of the tongue and the - mylohyoid, superior long
• The Bolus is then squeezed backwards by - genioglossus, contracts peristaltically, pushing bolus to back of tongue
• The tongue bulges into the oropharynx preventing food returning to oral cavity
• This relies on the muscles of the - mylohyoid, styloglossus, palatoglossus
• The posterior Oral cavity then starts closing via approximation of faucial pillars
• The closing process requires the muscles - palatoglossus, palatopharyngeus
• The phases of swallowing can start to fall apart if there is any level of stasis to the muscle.

Pharyngeal Stage

• There is a pharyngeal STAGE occurs over (approx ~2-sec)
• The Swallowing reflex is triggered as bolus stimulates tactile receptors on the fauces and uvula
• The process Soft palate needs ti raised and close nasal cavity at same time open bacк от оган
• The individual will experiemce Respiration to cease due to the soft palate being raised
• Next the Vocal folds are forces to close
• Larynx then raises hence epiglottis and becomes more closed over airway entrance
• To complete this the Geniohyoid draws hyoid forward allowing opening of pharynx

Mechanisms Preventing Food Passing Into Larynx

• The Soft palate has to be raised LVP
• Tensing of soft palate using force TVP
• The posterior pharyngeal wall should use superior constrictor
• When there is a By approximation of palatoglossal arches the palatoglossus helps prevent food pass in to the cavity
• The Muscles the mylohyoid, styloglossus control elevation of toungue.
• Muscles that provide elevation of the hyoit and laryn include: elvation of hyoid, larynx, which folds epiglottis to provide cover for inlet of laryngeal suprahyoids,
• Muscles that allow approximation , aryepiglottic, Vocal fold addutctors will provide the folding and addication of folding and close the vocal fold