5. Tongue

**Oral cavity regional relationships**

* Superior: Hard palate, maxillary alveolar ridge
* Lateral: Cheek-buccal space
* Inferior: Mylohyoid muscle (floor of mouth), mandibular alveolar ridge, and teeth
* Posterior: Soft palate, anterior tonsillar pillars, & lingual tonsil (tongue base)

**Tongue**

* Oral tongue: Anterior 2/3 of tongue

* Base of tongue: Posterior 1/3 in the oropharynx
* Root of tongue: Undersurface of oral tongue at its junction with anterior floor of mouth and mandible. Deep muscles of oral tongue (genioglossus and geniohyoid) + lingual septum
* Floor of mouth: Crescent-shaped region of mucosa overlying mylohyoid and hyoglossus muscles, extending from inner aspect of lower alveolar ridge to undersurface of anterior oral tongue

Oral tongue: Extrinsic tongue muscles

* Genioglossus: Large, fan-shaped muscle lying parallel to lingual septum
	+ Origin (O): Upper genial tubercle & internal surface of symphysis menti of mandible
	+ Insertion (I): Along length of tongue under surface
	+ Function (F): Protrudes tongue
	+ Innervation (N): CN12
* Hyoglossus: Thin, quadrilateral-shaped muscle
	+ O: Body & greater cornu of hyoid bone
	+ I: Passes vertically to insert into side of tongue
	+ F: Depresses tongue
	+ N: CN12
* Styloglossus
	+ O: Styloid process & stylomandibular ligament
	+ I: Side of tongue, merges with hyoglossus
	+ F: Retracts tongue upward & backward
	+ N: CN12
* Palatoglossus
	+ O: Undersurface of palatine aponeurosis
	+ I: Side and dorsum of tongue
	+ F: Forms anterior tonsillar pillar
	+ N: CN10, pharyngeal plexus branch

* Mylohyoid muscle
	+ Forms floor of mouth; separates lower OC into SMS and SLS except along posterior margin
	+ Mylohyoid cleft at junction of anterior 1/3 and posterior 2/3 of mylohyoid muscle
		- Contains fat ± vessels ± accessory salivary tissue
	+ O: Arises from mylohyoid line of mandible
	+ I: Hyoid bone
	+ F: Depresses mandible, elevates hyoid bone, OC floor, & tongue
	+ N: Mylohyoid nerve branch from CNV3
* Oral mucosal space/surface
	+ Lines entire oral cavity including buccal (cheeks), gingival (gums), palatal, and lingual surfaces
* Pterygomandibular raphe
	+ Fibrous band extending from posterior mandibular mylohyoid line to medial pterygoid plate hamulus
	+ Buccindfdfator and superior pharyngeal constrictor meet at pterygomandibular raphe
	+ Lies beneath mucosa of retromolar trigone
	+ Perifascial route of spread for SCCa from retromolar trigone to base pterygoid plates

Innervation of tongue

* Sensory supply (touch, pain, temperature and taste)
	+ Anterior 2/3: Lingual nerve (taste fibers are from chorda tympani branch of CN7)
	+ Posterior 1/3: CN9
* Hypoglossal nerve (CN12)
	+ Emerges from nasopharyngeal carotid space
	+ Receives fibers from 1st and 2nd cervical nerves
	+ Loops inferiorly to level of hyoid bone
	+ Rises anteriorly to enter posterior sublingual space just lateral to hyoglossus muscle
	+ Runs in sublingual space on lateral surface of genioglossus muscle
	+ Innervates extrinsic and intrinsic tongue muscles

Vasculature of tongue

* Lingual artery: 2nd branch of external carotid artery
	+ Divides in sublingual space into sublingual and deep lingual branches
* Lingual vein: Parallels lingual artery; drains into internal jugular or facial veins

Oral tongue lymph vessels

* Two systems: Superficial mucosa and deep collecting
* Superficial system: Crossing vessels in anterior floor of mouth drain bilaterally into anterior submandibular nodes
* Deep collecting system: Drain into ipsilateral anterior submandibular nodal chain only