L8: Oral cavity and submandibular gland

Question 1

Clinical relevance of oral cavity

Answer 1

ORAL ULCER - more than 7 days, in 95% is cancer
Tonsillitis
Tumours
Trauma (e.g. piercings)
Congenital disorders

Question 2

Surface anatomy

Answer 2

• Lingual v running with lingual a and n
• Sublingual fold overlying sublingual gland (2 openings of gland along fold)
• Submandibular duct either side of frenulum with 1 opening
• Sublingual caruncles (prominences)
• Frenulum = membrane attaching tongue to base of oral cavity (can be tongue tied if extends too far forward)

Question 3

Clinical: piercing

Answer 3

Piercing of tongue may damage lingual n causing loss of taste and sensation to ant 2/3 of tongue

Question 4

Back of oral cavity surface anatomy

Answer 4

Soft palate and uvula (extension of soft palate)

Either side is palatine tonsil between palatopharyngeal arch and palatoglossal arch

Question 5

Surface of tongue

Answer 5

• (Front) fungiform papillae
• Filiform papillae
• Vallate papillae (V shaped, ant to terminal sulcus)
• Pharyngeal part of tongue post to terminal sulcus
• Foramen cecum: where pharyngeal tonsils meet at midline (thyroid first develops here in embryology)

Question 6

Oral cavity boundaries

Answer 6

Roof: hard and soft palates (palatine process of maxilla - ant 3/4, horizontal plates of palatine - post 1/4)
Floor: muscular diaphragm and tongue
Lateral walls: oral mucosa, fascia, buccinator

Opens anteriorly to oral fissure, posteriorly to oropharyngeal isthmus

It is below nasal cavity, above larynx

Question 7

Lateral walls - cheeks

Answer 7

Buccinator
- Attached posteriorly to pterygomandibular raphe
- In same plane as sup constrictor muscle of pharynx
= continuity between walls of oral and pharyngeal cavities
- Holds cheeks against alveolar arches and keeps food between teeth when chewing
- Innervated by facial n [VII]

Question 8

Floor of oral cavity

Answer 8

Paired mylohyoid muscles joined at midline by raphe

• Has free posterior margin
• Attached anteriorly to mandible at mylohyoid line
• Posteriorly to hyoid bone
• Innervated by mandibular n [V3]

Geniohyoid is deep to mylohyoid, originates from inferior mental spines
- Innervated by C1

Question 9

Gateway into oral cavity

Answer 9

Triangular aperture/oropharyngeal triangle

• Between mylohyoid, sup constrictor, middle constrictor
• Structures enter and leave oral cavity: lingual n, hypoglossal n, glossopharyngeal n and arteries get into oral cavity

Question 10

Muscles of tongue - intrinsic

Answer 10

ALL innervated by hypoglossal n [XII]
(Origin and insertion within tongue)
1. Superior longitudinal
2. Vertical
3. Transverse
4. Inferior longitudinal
5. Septum (at midline)

Question 11

Muscles of tongue - extrinsic

Answer 11

ALL innervated by hypoglossal n [XII] EXCEPT palatoglossus is by vagus [X] (all structures from palatine bone incl. soft palate are innervated by vagus nerve)
1. Palatoglossus
2. Styloglossus
3. Hyoglossus (hyoid bone to tongue)
4. Genioglossus (sup mental spines to tongue)
(important for moving tongue so we can speak)

Question 12

Muscles from superficial to deep

Answer 12

Skin - mylohyoid - geniohyoid - genioglossus

Question 13

2 potential spaces and their contents

Answer 13

First: between mylohyoid and hyoglossus

• Lingual n (from V3)
• Chorda tympani (from VII): ant 2/3 taste
• Hypoglossal n [XII]
• Deep lingual v

Second: between hyoglossus and genioglossus

• Glossopharyngeal n [IX]: post 1/3 taste
• Lingual a
• Dorsal lingual v

Question 14

Course of hypoglossal nerve

+ relation to lingual nerve

Answer 14

Crosses lateral to internal and external carotid arteries (with deep lingual vein) and goes deep to mylohyoid via triangular aperture to enter potential space between mylohyoid and hyoglossus

Lingual and hypoglossal in same lateral to medial plane but lingual is more superior than hypoglossal

Question 15

Course of glossopharyngeal nerve

Answer 15

Runs between internal and external carotid into triangle aperture, then enters second potential space between hyoglossus and genioglossus

Question 16

Submandibular gland features

Submandibular duct

Answer 16

Has superficial and deep parts
Wraps around free edge of mylohyoid muscle

To reach gland must dissect through: skin, subcutaneous fat, platysma and investing layer of deep cervical fascia

Submandibular (Wharton) duct originates from superficial part of gland but emerges from deep part and terminates next to sublingual papilla next to base of frenulum of tongue

Question 17

Muscles associated with submandibular gland

Structures running across gland

Answer 17

Muscles: mylohyoid, hyoglossus and posterior belly of digastric (all important structures under post belly)

Structures running across: facial v, facial a and lymph nodes

Question 18

Nerves at risk in submandibular excision

Answer 18

Marginal mandibular branch of facial nerve, hypoglossal nerve, lingual nerve

Question 19

Where would you site incision for submandibular gland excision?

Answer 19

About 4cm below and parallel to lower border of mandible to avoid injury to marginal mandibular branch of facial nerve

Question 20

What structures running across submandibular gland must be ligated and divided in submandibular gland excision?

Answer 20

Facial vein lies over surface of gland
Facial artery arches over and grooves the post part of gland as it passes forward between it and mandible. As it hooks under lower border of mandible it is closely related to marginal mandibular branch of VII and gives off submental artery at this point.
Lymph nodes may be adherent to surface of gland

Question 21

Marginal mandibular nerve path

+ damage

Answer 21

Lies between investing layer of deep cervical fascia and platysma (superficially).
Passes downward from parotid and lies up to 2.5cm below border of mandible.
Passes forward to cross facial artery, facial vein and lower border of mandible to supply lower lip

DAMAGE: flattening and inversion of ipsilateral lower lip

Question 22

Lingual nerve path

+ damage

Answer 22

Lingual n (and submandibular ganglion) lies above deep portion of submandibular gland and loops under duct from lateral to medial deep to mylohyoid on surface of hyoglossus

DAMAGE: loss of sensation and taste to anterior 2/3 of ipsilateral tongue and floor of mouth
(taste supplied by chorda tympani)

Question 23

Hypoglossal nerve path

+ damage

Answer 23

Runs below deep part of gland medial to posterior belly of digastric and passes forwards deep to mylohyoid. Purely motor to ipsilateral tongue

DAMAGE: may cause dysarthria

Question 24

Roof of oral cavity

Hard and soft palate

Answer 24

(Maxilla and palatine bones)
Anterior hard palate and posterior soft palate

Hard palate:
- Palatine process of maxillae 
  (ant 3/4)
- Horizontal plates of palatine 
  bone (post 1/4)
- Anteriorly palatine rugae, 
  incisive papilla overlying 
  incisive foramen

Soft palate:
- Ends at uvula
- (post nasal spine where 2 
  horizontal plates of palatine 
  bone meet)
- Palatopharyngeal arch (more 
  post) and palatoglossal arch

Question 25

Innervation and arterial supply of soft palate

Answer 25

Innervation: lesser and greater palatine nerves through lesser and greater palatine foramen (V3)

Arterial: lesser and greater palatine arteries from infratemporal and pterygopalatine fossa (branches of maxillary), ascending palatine artery from facial artery

Question 26

Lymphatic drainage of oral cavity

Answer 26

To regions 1 and 2 in the neck

Question 27

Muscles of soft palate

Answer 27

1. Tensor veli palatini
2. Levator veli palatini
3. Palatopharyngeus
   Palatine tonsil –>
4. Palatoglossus
5. Musculus uvulae

1 is supplied by [V3] and rest by pharyngeal plexus of [X]