Download TSM31 - Mouth and Tongue

TSM31: MOUTH AND TONGUE
14/10/08
LEARNING OUTCOMES
Describe the anatomy of the oral cavity



The oral cavity is bounded:
o Inferiorly by the tongue and floor of mouth muscles (see below)
o Superiorly by the hard palate
o Laterally by the cheeks
o Posteriorly by the soft palate
The uvula hangs down from the roof of mouth as an extension of the soft palate
o The palatoglossal arch is a soft arch immediately posterior to the uvula
o 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:
o 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)
o 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
o 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
o The frenulum linguae is a central mucous membrane fold linking it to the floor of mouth
o 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
o Vallate papillae are found anterior and parallel to the terminal sulcus
o Foliate papillae are found on the lateral edges of the tongue
o Fungiform papillae are found medial to the foliate papillae
o Filiform papillae are found most medially and are the thinnest projections
Gustatory and sensory innervation to the tongue is divided according to the parts:
o Oral part – sensory lingual nerve (of V3); gustatory chorda timpani (of facial nerve)
o 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:
o 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
o 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
o All of the above except palatoglossus are innervated by the hypoglossal nerve (CNXII)
 The hypoglossal nerve provides the sole motor supply to the tongue
 Palatoglossus is supplied by the vagus nerve (CNX)
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)
o Arises at the posterior part of the tympanic cavity
o Passes beneath the inner surface of the tympanic membrane
o Passes through the temporal bone to the infratemporal fossa
At the infratemporal fossa it joins the lingual nerve (branch of trigeminal V3)
o Travels inferiorly along the oral cavity
o Passes beneath the submandibular duct
o Parasympathetic supply to all glands below the oral fissure including all salivary glands
o Conveys gustatory sensory information from oral part of tongue
HYPOGLOSSAL NERVE


Arises from the hypoglossal nucleus near the midline in the dorsal caudal medulla
o Fibres travel along the medial lemniscus and emerge between the pyramid and olive
o Descends through the hypoglossal canal below the angle of the mandible
o Moves anteriorly crossing over the external carotid artery
o Follows the hyoglossus muscle to the tongue
Damage to the hypoglossal nerve can be tested through asking the patient to protrude their tongue
o Nerve supply to the two halves of the tongue is ipsilateral
o 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
o Anteriorly there are numerous longitudinal ridges – palatine rugae


The soft palate is continuous with the hard palate and extends posteriorly into the oropharynx
o It acts as a valve between the naso- and oropharynx
Several muscles are involved in the movement of the soft palate:
o 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)
o Levator veli palatini – elevates the soft palate (only muscle to do so)
 Inserts from base of skull directly onto palatine aponeurosis
o 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
o 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
o All of the above muscles are innervated by branches of the vagus nerve (CNX) except:
 Tensor veli palatini which is innervated by trigeminal V3