Anatomy and physiology of the throat

Question 1

What are the two components of the oral cavity?

Answer 1

– Oral vestibule (between lips and teeth)

– Oral cavity proper

Question 2

What are the boundaries of the oral cavity?

Answer 2

– Lips to palatoglossal arch (anterior pillar)
– Palate to floor of mouth/tongue
– Buccal mucosa

Question 3

What are the functions of the oral cavity?

Answer 3

• Taste
• Mastication - Teeth, tongue
• Speech - Tongue, cheek, lips
• Digestion - Salivary enzymes
• Swallowing - Tongue, hard and soft palate

Question 4

What nerve innervates the anterior 2/3rds of the tongue?

Answer 4

Lingual nerve (branch of CN V3)

Question 5

What divided the submandibular salivary duct into the superficial and deep lobe?

Answer 5

Mylohyoid muscle

Question 6

Describe the two parts of the tongue, their embryological origin and its innervation

Answer 6

Anterior 2/3rd
• From 1st branchial arch
• Sensation by lingual nerve (branch of CN V3)
• Taste by chorda tympani (branch of CN VII)

Posterior 1/3rd
• From 3rd branchial arch
• Supplied by CN IX (glossopharyngeal) nerve

Question 7

What is the difference between intrinsic and extrinsic tongue muscles?

Answer 7

o Intrinsic muscles (alter shape)

o Extrinsic muscles (alter position) - genioglossus, styloglossus, hyoglossus and palatoglossus.

Question 8

Describe the nerve supply of the tongue muscles

Answer 8

CN XII: hypoglossal nerve supply all muscles except for palatoglossus – pharyngeal plexus (CN IX - X)

Question 9

What are the functions of the tongue?

Answer 9

o Taste
o Mastication
o Swallowing
o Speech

Question 10

What are the 4 muscles of mastication?

Answer 10

o Lateral pterygoid
o Medial pterygoid
o Temporalis
o Masseter

Question 11

What is the nerve supply for the muscles of mastication?

Answer 11

CN V3 (mandibular branch of trigeminal)

Question 12

Describe the epithelium of the oropharynx

Answer 12

Stratified, non-keratinised squamous

Question 13

Describe the oropharynx

Answer 13

The oropharynx is the middle part of the throat that includes the base of the tongue, the tonsils, the soft palate, and the walls of the pharynx.

Question 14

What has been linked to the recent increase in oropharyngeal cancers?

Answer 14

HPV infections

Question 15

Describe the nerve supply of the oropharynx

Answer 15

Pharyngeal plexus- CN IX & X

Question 16

Describe the blood supply of the hypopharynx

Answer 16

Superior Thyroid Artery, the Lingual Artery and the Ascending Pharyngeal Artery.

Question 17

Describe the nerve supply of the hypopharynx

Answer 17

Pharyngeal plexus- CN IX & X

Question 18

Describe the hypopharynx

Answer 18

The hypopharynx is the part of the throat (pharynx) that lies beside and behind the larynx. The hypopharynx is the entrance into the esophagus. Food goes from the mouth and through the hypopharynx and esophagus, where it then passes into the stomach.

Question 19

What are the 3 phases of swallowing?

Answer 19

Oral phase (voluntary) – in oral cavity
•	Tongue propels food (bolus) into pharynx
•	Triggering swallowing reflex (afferent: CN V, IX, X – swallowing centre in medulla – efferent: CN VII, X, XII)

Pharyngeal – in pharynx
• Soft palate pulled upwards
• Epiglottis covers the larynx, vocal cord approximate, larynx moves upward
• Upper oesophageal sphincter (UOS) relaxes
• Respiration reflex inhibited

Oesophageal – enters oesophagus
• Once bolus passed UOS, the sphincter constricts
• Bolus propelled downwards by peristaltic motion, reflex via myenteric plexus

Question 20

What are the afferent fibres that tell the swallowing centre in the medulla to trigger the swallowing reflex?

Answer 20

afferent: CN V, IX, X

Question 21

What are the efferent fibres that trigger the swallowing reflex?

Answer 21

CN VII, X, XII

Question 22

What controls the peristaltic reflex of food movement down the oesophagus?

Answer 22

Auerbach’s plexus (or myenteric plexus)

Question 23

What are the functions of the larynx?

Answer 23

o Part of respiratory tract
o Voice
o Swallowing

Question 24

What are the 3 parts of the larynx?

Answer 24

o Supraglottis: extends from the superior tip of the epiglottis to the floor of the ventricular fold (junction of respiratory and squamous epithelium).

o Glottis: begins superiorly at the true vocal fold and extends inferiorly to a horizontal plane 5 mm inferior to the vocal cord

o Subglottic: begins 5 mm below the free edge of the true vocal cord and proceeds to the inferior border of the cricoid cartilage

Question 25

What are the 7 segments of cartilage which make up the larynx?

Answer 25

o Cricoid cartilage
o Thyroid cartilage
o Epiglottis
o Paired arytenoid cartilages (corniculate and cuneiform)

Question 26

What are the functions of the extrinsic and intrinsic muscles of the larynx?

Answer 26

Extrinsic muscles (infrahyoid, suprahyoid, and thyrohyoid) of the larynx move the entire laryngeal complex while intrinsic muscles regulate movement of the vocal folds.

Question 27

Describe the motor innervation of the larynx

Answer 27

All intrinsic mucles supplied by recurrent laryngeal nerve except for cricothyroid muscle (external laryngeal nerve)

Question 28

Describe the sensory innervation of the larynx

Answer 28

o Supraglottic: internal laryngeal nerve

o Glottic and subglottic: recurrent laryngeal nerve

Question 29

Which nerve close to the larynx has a greater chance of injury?

Answer 29

The left recurrent laryngeal nerve has a longer course since it loops around the aortic arch instead of the right subclavian artery and therefore has a higher risk of injury during operative chest procedures.

Question 30

Where does the superior laryngeal nerve split and what into?

Answer 30

At the level of the greater horn of the hyoid, the superior laryngeal nerve divides into an internal and an external branch.

The internal branch travels with the superior laryngeal artery through the thyrohyoid membrane and allows supraglottic sensation and increased airway protection.

The external branch supplies subglottic mucosal sensation and motor fibers to the cricothyroid muscle.

Question 31

What are the 5 components of speech?

Answer 31

Respiration

• Source of energy: air flow
• Inhalation and exhalation

Phonation
- Flow of air through different VC position, tension, vibration & length

Resonation

• Oral/nasal speech balance
• Depend on nasopharynx, nasal cavity & oral cavity

Articulation
- Production of speech determined by action of lips, tongue and jaw

Prosody

• Production of syllable stress and emphasis
• Provide effective speech tone

Question 32

Describe the production of speech

Answer 32

The pulmonary phase creates the energy flow with inflation and expulsion of air. This activity provides the larynx with a column of air for the laryngeal phase.

In the laryngeal phase, vocal folds vibrate at certain frequencies to create sound that is then modified in the supraglottic/oral/nasal phase. This modified sound is considered a unique individual voice.

Words are formed by the action of the pharynx, tongue, lips, and teeth. Dysfunction in any of these stages can lead to voice changes, which may be interpreted as hoarseness by the patient.

Question 33

Which area of the brain is associated with prosody?

Answer 33

Prosody is the rhythm, stress and intonation of speech. It is associated with Brodmann areas 44 and 45 (Broca’s area) of the left frontal lobe