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The mouth

  • The mouth consists of a small vestibule outside the teeth and a much larger, inner oral cavity proper. The oral cavity proper is bounded anterolaterally by the alveolar arches, teeth and gums (gingivae); behind it communicates with the pharynx via the oropharyngeal isthmus. Its roof is formed from the hard and soft palates, most of its floor by the anterior region of the tongue and the remainder by the reflection of the mucosa from the tongue's inferior surface to the internal mandibular surface.

The vestibule is bounded by the lips, which are covered by skin externally and by mucous membrane internally. Internally, each lip is connected to the gum by a median labial frenulum. The orbicularis oris muscle lies between the two surfaces (supplied by CN VII). Labial glands are situated between the mucosa and the orbicularis oris; their ducts opening into the vestibule.

Cavity of the mouth

  • The roof of consists of hard palate and soft palate both covered by mucosa. The muscles of the soft palate will be discussed later. The bony palate consists of the palatine process of maxilla, joined by intermaxillary suture. Anterior to this suture lies the incisive foramen, with orifices of two incisive canals, transmitting nerves and vessels. Posteriorly the hard palate consists of the paired horizontal plates of the palatine bones.


  • Floor
    • Muscles (from above downwards):
      • Geniohyoid
      • Mylohyoid (diaphragma oris)
      • Anterior belly of the digastric
      • Stylohyoid
    • Features:
      • Frenulum of the tongue: connecting the lower surface of the tongue to the floor. The lower end of the frenulum presents an elevation, the sublingual papilla, on which the submandibular duct opens
      • Sublingual fold: produced by sublingual gland, contains openings of sublingual ducts
  • Diagram: viewing the floor of the mouth with the tongue removed, can see the curve of the mandible and the hyoid bone
  • Geniohyoid muscle is a strap running forward from the hyoid bone
  • The mylohyoid muscle is inferior to the geniohyoid muscle and is a membrane that forms a complete floor to the oral cavity
  • Diagram: view from below
  • Note the lesser cornura of the hyoid bone
  • There is a little tether (loop) attached to those cornura, and there is a muscle that is arranged in two bellies with a little snip passing through the little loops. This is the digastric muscle (anterior belly and the posterior belly).
  • The mylohyoid muscle is also shown

So from superior to inferior: geniohyoid muscle, mylohyoid muscle, and digastric muscle

The tongue

  • A highly muscular organ of swallowing, taste and speech
  • Has a root, apex, curved dorsum and inferior surface
  • Consists of oral (presulcal) and pharyngeal (postsulcal) parts, separated by the sulcus terminalis, a V-shaped groove running to the bases of the palatoglossal arches.
  • Moves food around in mouth, important for speech, important in infants for compressing the nipple against the hard palate
  • There's an anterior 2/3 and a posterior 1/3

Dorsum of tongue

  • Foramen caecum: site of origin of the thyroid diverticulum during development. Located at point of sulcus terminalis "V".
  • Median sulcus: extending from the median glosso-epiglottic fold to the apex of the tongue.
  • Lingual tonsil: in the postsulcal part, consists of multiple lymphoid nodules embedded in the submucosa
  • Epiglottic vallecula: between the median and lateral glosso-epiglottic folds in the postsulcal part
  • Lingual papillae (4 principal types):
    • Filiform: small, conical or cylindrical, arranged in rows parallel to vallate papillae. Cover most of the presulcal part of the dorsum. Do not bear taste buds, but increase friction
    • Vallate (circumvallate): 8 to 12 in number. Arranged in front of sulcus terminalis (V-shape). One to two mm in diameter, consist of papilla surrounded by sulcus, which is in turn surrounded by a wall (vallum). Taste buds lie in both sulcal walls.
    • Fungiform: occur mainly on the lingual margin. Large round shape, deep red colour. Bear taste buds.
    • Foliate: grooves and ridges at the lateral margins of the tongue near the palatoglossal arch. Contain taste buds.


  • Down the back, we see the epiglottis (cartilage flap protecting the entrance to the larynx)
  • There are folds that join the epiglottis to the back of the tongue (part of spring loading allowing it to flop back after swallowing). This is called the glossoepiglottic fold
  • Palatoglossal and palatopharyngeal arches
    • Both start from the palate
    • One runs back to the pharynx
    • One runs forward to the tongue
    • These are separated by the tonsillar fossa (containing the palatine tonsils)
  • Sulcus terminalis divides the dorsum of the tongue into an anterior 2/3 and a posterior 1/3
    • Posterior part of the tongue is called the pharyngeal part; anterior part is called the oral part of the tongue (lying in the true oral cavity)
  • The pharyngeal part of the tongue contains the lingual tonsil
  • 3 main sets of tonsillar tissue: palatine, lingual and the nasal tonsils
  • Where the two limbs of the grooves of the sulcus terminalis meet, there may be a depression - called the foramen caecum
    • This is the site where your thyroid gland originates in embryology
  • On the side of the tongue, there is striping. These are called the foliate papillae, containing some tastebuds (sour taste)
  • Circumvallate papillae - 9-12 structures in front of the sulcus terminalis that look like castles with a moat - these are taste buds
  • Fungiform papillae - look like tiny mushrooms on the surface of the oral part of the tongue
  • Filiform papillae are like conical projections, designed to rip food (cats have these; used for grooming themselves with their tongue)

Inferior tongue surface

  • Frenulum: of the tongue connecting tongue to floor of mouth
  • Profunda linguae vein: is visible on either side of the frenulum
  • Plica fimbriata: a fold of mucous membrane, lies on the lateral side of the vein
  • Frenulum of tongue - midline flap of mucosa. Sometimes, in young children, this anchors the tongue to the mouth (tongue-tied); can stop you speaking (need surgery).
  • To the sides of the frenulum, there are folds (plica fimbriata)
  • Blue structures to the sides of the frenulum are the deep lingual veins
  • At the bottom of the frenulum are bumps - the sublingual papilla
  • To the side of the sublingual papilla is a fold - the sublingual fold
    • The papilla and fold are important as they are the openings for the sublingual and submandibular salivary glands

Muscles of the tongue

  • Made of skeletal muscle
  • We normally divide the tongue muscles into:
    1. Those inside the tongue itself - to change the shape of the tongue (intrinsic muscles)
    2. Those which insert into the tongue - to move the tongue (extrinsic muscles)
Muscle Origin Insertion Function
Intrinsic
Superior Longitudinal muscle(just beneath surface of the tongue) Submucosal connective tissue at the back of the tongue and from the median septum of the tongue Muscle fibers pass forward and obliquely to submmucosal connective tissue and mucosa on margins of the tongue Shortens tongue, curls apex and sides of the tongue
Inferior Longitudinal muscle (Between Genioglossus and hyoglossus) Root of tongue Apex of tongue Shortens tongue, uncurls apex of the tongue
Transverse muscles Median septum of the tongue Submucosal connective tissue on lateral margins of tongue Narrows and elongates tongue
Vertical muscles Submucosal connective tissue on dorsum of the tongue Connective tissue in more ventral regions of tongue Flattens and widens tongue
Extrinsic
Genioglossus Superior mental tubercles Body of hyoid, entire length of tongue Protrudes tongue, depresses centre of tongue
Hyoglossus Greater horn and adjacent part of the body of the hyoid bone Lateral surface of tongue Depresses tongue
Styloglossus Styloid process Lateral surface of the tongue Elevates and retracts tongue
Palatoglossus Inferior surface of palatine aponeurosis Lateral margins of tongue Depresses palate, moves palatoglossal arch towards midline, elevates the back of tongue

Sensory innervation of tongue

  • Oral part
    • Lingual nerve: (from mandibular division of CN V) for general sensation
    • Chorda tympani: (from CN VII) for taste
  • Pharyngeal part and vallate papillae:
    • Lingual branch of the glossopharyngeal nerve: for both taste and general sensation. Near the epiglottis the internal laryngeal branch of the vagus provides general sensation and taste

The soft palate

  • Suspended from the hard palate
  • Acts as a partition between the nasopharynx and the oropharynx
  • Possesses a median conical process, the uvula, from its posterior edge
  • Two curved folds of mucosa containing muscle extend laterally from the base of the uvula: palatoglossal arch, palatopharyngeal arch
  • Between these two arches lies the palatine fossa, containing the palatine tonsil.
  • The palatine aponeurosis (thin and fibrous) supports the muscles and strengthens the soft palate. It attaches to the posterior border and inferior surface of the hard palate. It thins as one proceeds posteriorly and encloses the uvulae muscle in the midline.
  • Uvula - hangs down from the soft palate at the back of the mouth
  • Above the soft palate we can see the entrance into the nasal cavity
  • Usually the palate should move symmetrically (both sides move in unison)
  • Muscles insert into the palate from many different directions. The soft palate itself is a CT sheet and is moved around by these muscles.
Muscle Origin Insertion Function
Palatoglossus muscle Inferior surface of palatine aponeurosis Lateral margin of tongue Elevates the back of tongue, depresses palate (closes the oropharyngeal isthmus)
Palatopharyngeus muscle Superior surface of palatine aponeurosis Pharyngeal wall Elevates pharynx, depresses soft palate
Levator veli palatini muscle Petrous part of the temporal bone,(base of skull) anterior to opening for carotid canal Superior surface of palatine aponeurosis Elevates soft palate
Tensor veli palatini Sphenoid bone Palatine aponeurosis Tenses soft palate
  • Hanging down from the soft palate is the uvula, which has its own muscle - the musculus uvulae
  • Most of the muscles of the soft palate are supplied by the vagal nerve. However the tensor veli palatini muscle is innervated by the trigeminal nerve.
  • Ask the patient to say "ahh" - this tests the symmetrical elevation of the soft palate (vagal nerve)
  • Hypoglossal nerve - nervous supply to the intrinsic and extrinsic muscles of the tongue (from the vagus nerve) except for the Tensor veli palatini muscle and another muscle - intrinsic


Pharynx

  • Has three parts: nasopharynx, oropharynx and laryngopharynx


  • 3 different parts of the pharynx
    • Nasopharynx (directly behind the nasal cavity - base of skull to the uvula)
    • Oropharynx (directly behind the oral cavity - uvula to epiglottis)
    • Laryngopharynx (directly behind the larynx - tip of epiglottis down to the cricoid cartilage)
  • These 3 parts are only present in humans who have grown beyond the first 12 months of life. The epiglottis of a baby sits up very high (above the uvula) - this allows it to breathe while suckling - but it needs to lower to allow speech
  • View of the pharynx from behind
    • Note the piriform fossae

Nasopharynx

  • lies behind the nose and above the soft palate
  • Communicates with the oropharynx by the pharyngeal isthmus (bounded by soft palate and posterior pharyngeal wall), which is closed during swallowing by elevation of the soft palate and contraction of the palatopharyngeus.
  • Each lateral wall possesses a pharyngeal opening of the auditory tube. This opening is bounded above and behind by a tubal elevation.
  • A vertical salpingopharyngeal fold of mucosa descends from the tubal elevation, covering the salpingopharyngeus muscle
  • Pharyngeal recess lies behind the tubal elevation
  • The pharyngeal tonsil, a lymphoid tissue, lies in the submucosa of the posterior wall


  • Diagram: view into the nasopharynx from behind
  • We see the nasal septum, the nasal conchae, the soft palate and the uvula. Note the tubal elevation on the side wall of the nasal cavity (containing the opening of the auditory tube underneath its rim). Pharyngeal recess is the space between it and the back wall . The pharyngeal opening of the auditory tube connects the middle ear with the nasopharynx - this allows your middle ear to equalise pressure with the outside environment. Therefore you don't get pressure buildup inside the ear - not only is this painful but it would not allow the eardrum to move readily. It's also necessary to drain out fluid (secretions, infectious material).
  • Connecting the nasopharynx with the middle ear allows infections from the nasopharynx to spread up to the middle ear - producing otitis media


Oropharynx

  • Extending from the soft palate to the upper border of the epiglottis
  • Lateral wall consists of the palatopharyngeal arch and the palatine tonsil. The latter sits in the tonsillar fossa or sinus between the palatoglossal and palatopharyngeal arches, behind the 3rd lower molar tooth. The palatine tonsil is the chief component of Waldeyer's ring, which consists of the palatine, pharyngeal, tubal and lingual tonsils. The ring of lymphoid tissue forms a protective annulus around the entrance to the digestive and respiratory tracts, providing humoral and cellular defence against infection of the oral and nasal cavities and pharynx.
  • The third component of Waldeyer's rim- the tonsillar tissue, is located in the nasopharynx.
    • Tubal tonsils
    • Pharyngeal tonsils
  • Note: Tubal tonsil, salpingopharyngeal fold, nasopharyngeal tonsil (grey area). Tonsil inflammation can interfere with drainage from middle ear, and can even stop you breathing through your nose.


Laryngopharynx

  • Extends from the cranial border of the epiglottis (lower CV3 body) to the inferior border of the cricoid cartilage (upper CV 6 body), where it becomes continuous with the oesophagus
  • Anterior wall contains the laryngeal inlet, bounded laterally by the aryepiglottic folds. On either side of these in turn lies the piriform fossae. Foreign bodies may lodge in the piriform fossa.
  • Note: vallecula (little recess in which pointy things coming down the back of the tongue can get stuck), the laryngeal inlet and the aryepiglottic fold


Pharyngeal musculature

  • Inferior, middle and superior pharyngeal constrictors


  • Mostly the pharyngeal muscles are arranged as sloped rings encircling the circumference of the pharynx - when they contract, they act as constrictors of the pharynx
  • Other muscles inserting from the side move it around and pull the tube up and so on
  • Pharyngobasilar fascia
  • Median pharyngeal raphe (midline seam)
  • Constrictors
    1. Superior pharyngeal constrictor
    2. Middle pharyngeal constrictor
    3. Inferior pharyngeal constrictor (upper part = thyropharyngeus, lower part = cricopharyngeus)
  • These muscles are designed to constrict things in the pharynx (to squeeze food down - pushes the bolus down into the oesophagus where peristalsis pushes it down into the stomach)
  • All these constrictors are supplied by the vagus nerve. Therefore neurological conditions of the vagus nerve affect swallowing

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