Tsm31: mouth and tongue 14/10/08 Learning Outcomes

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TSM31: mouth and tongue 14/10/08

Learning Outcomes

Describe the anatomy of the oral cavity

  • The oral cavity is bounded:

    • Inferiorly by the tongue and floor of mouth muscles (see below)

    • Superiorly by the hard palate

    • Laterally by the cheeks

    • Posteriorly by the soft palate

  • The uvula hangs down from the roof of mouth as an extension of the soft palate

    • The palatoglossal arch is a soft arch immediately posterior to the uvula

    • The palatopharyngeal arch is another soft arch and the anterior border of the oropharynx

  • The palatine tonsils are situated between the palatoglossal and palatopharyngeal arches

floor of mouth

  • The floor of mouth itself is made up of two main muscles apart from the (superior-most) tongue itself:

    • The mylohyoid muscles are the sheet-like inferior-most muscles of the floor of mouth

      • Run from the sides of the mandible to the hyoid bone

      • Innervated by nerve to mylohyoid (inferior alveolar branch of trigeminal V3)

    • The geniohyoid muscles are cords that lie superior to mylohyoid along the midline

      • Arise from the superior mental tubercles and insert onto the medial hyoid bone

      • Innervated by C1

    • Both of the above depress the mandible when the hyoid is fixed and elevate the vice-versa

Describe the functional anatomy of the tongue

Overview of the tongue

  • The tongue (or glossa) is a muscular mass attached at its root to the floor of mouth

    • The frenulum linguae is a central mucous membrane fold linking it to the floor of mouth

    • It is divided into oral (ant. 2/3) and pharyngeal (post. 1/3) ‘parts’ by the terminal sulcus

  • Its surface is rough and appears furred due to the presence of minute surface projections – papillae

    • Vallate papillae are found anterior and parallel to the terminal sulcus

    • Foliate papillae are found on the lateral edges of the tongue

    • Fungiform papillae are found medial to the foliate papillae

    • Filiform papillae are found most medially and are the thinnest projections

  • Gustatory and sensory innervation to the tongue is divided according to the parts:

    • Oral part – sensory lingual nerve (of V3); gustatory chorda timpani (of facial nerve)

    • Pharyngeal part – both glossopharyngeal (CNIX); gustatory via vallate papillae only (CNIX)

  • Principal blood supply is from the lingual artery (branch of external carotid artery

muscles of the tongue

  • The tongue is divided in the midline by a connective tissue septum; as such all its muscles are paired

  • There are both intrinsic and extrinsic muscle groups:

    • The intrinsic muscles arise from the substance of the tongue itself

      • Superior and inferior longitudinal, vertical and transverse muscles

      • These alter the shape rather than the position of the tongue

    • The extrinsic muscles arise from structures external to the tongue and insert onto it

      • Palatoglossus arises from the soft palate and elevates the dorsum

      • Styloglossus arises from the styloid process and elevates / retracts the tongue

      • Hyoglossus arises from the hyoid bone and depresses the tongue

      • Genioglossus arises from the superior mental tubercles and protrudes the tongue

    • All of the above except palatoglossus are innervated by the hypoglossal nerve (CNXII)

Describe the course and distribution of the hypoglossal nerve and chorda tympani

chorda tympani

  • The chorda tympani is a branch of the facial nerve (CNVII)

    • Arises at the posterior part of the tympanic cavity

    • Passes beneath the inner surface of the tympanic membrane

    • Passes through the temporal bone to the infratemporal fossa

  • At the infratemporal fossa it joins the lingual nerve (branch of trigeminal V3)

    • Travels inferiorly along the oral cavity

    • Passes beneath the submandibular duct

    • Parasympathetic supply to all glands below the oral fissure including all salivary glands

    • Conveys gustatory sensory information from oral part of tongue

hypoglossal nerve

  • Arises from the hypoglossal nucleus near the midline in the dorsal caudal medulla

    • Fibres travel along the medial lemniscus and emerge between the pyramid and olive

    • Descends through the hypoglossal canal below the angle of the mandible

    • Moves anteriorly crossing over the external carotid artery

    • Follows the hyoglossus muscle to the tongue

  • Damage to the hypoglossal nerve can be tested through asking the patient to protrude their tongue

    • Nerve supply to the two halves of the tongue is ipsilateral

    • Deviation to one side indicates hypoglossal nerve damage on the ipsilateral side

Describe the anatomy of the palate

  • The palate is divided into hard (anterior) and soft (posterior) regions

  • The hard palate has a bony roof formed by the palatine process of the maxilla and palatine bones

    • Anteriorly there are numerous longitudinal ridges – palatine rugae

  • The soft palate is continuous with the hard palate and extends posteriorly into the oropharynx

    • It acts as a valve between the naso- and oropharynx

  • Several muscles are involved in the movement of the soft palate:

    • Tensor veli palatini – tenses the soft palate; facilitates tympanic-oral pressure equalisation

      • Arises as bilateral muscular projections from the base of skull

      • Projections descend between the medial and lateral pterygoid plates

      • Hook around hamulus to form palatine aponeurosis (essentially the soft palate)

    • Levator veli palatini – elevates the soft palate (only muscle to do so)

      • Inserts from base of skull directly onto palatine aponeurosis

    • Palatopharyngeus depresses the soft palate; elevates the pharynx

      • Arises from superior surface of the palatine aponeurosis

      • Descends bilaterally along the pharyngeal walls

      • Forms palatopharyngeal arches

    • Palatoglossus – depresses the soft palate; elevates the dorsum of the tongue

      • Arises from inferior surface of the palatine aponeurosis

      • Inserts bilaterally onto the lateral margins of the tongue

    • All of the above muscles are innervated by branches of the vagus nerve (CNX) except:

      • Tensor veli palatini which is innervated by trigeminal V3

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