Deglutition

Question 1

What are the 3 phases of deglutition?

Answer 1

Oral phase
Pharyngeal phase
Oesophageal phase

Question 2

Describe the muscular movements in the first phase

Answer 2

1. Anterior tip of genioglossus protruded against hard palate
2. Palatoglossus relaxes and elevates
3. Hyoglossus contracts and depresses posterior part of tongue

Question 3

First phase:
How does the bolus move?
What does it trigger?

Answer 3

Bolus slides down to posterior third of tongue where it stimulates sensory fibres of the glossopharyngeal nerve (CN IX)

This triggers the swallowing reflex

Question 4

Describe the muscular movements in the second phase

Answer 4

1. Styloglossus contracts to pull tongue up and backwards
2. Nasopharynx is closed off by soft palate, which is lifted by tensor and levator veli palatini
3. Mylohyoid, digastric and stylohyoid contract, elevating front of tongue, the hyoid bone and the larynx

Question 5

Second phase:
How does the bolus move?
What does it trigger?

Answer 5

Elevation and retraction of tongue, and closing off of nasopharynx, forces bolus into oropharynx

Elevation of hyoid causes epiglottis to cover the opening of the larynx such that bolus passes over laryngeal inlet

When bolus reaches superior pharyngeal constrictor, it triggers a wave of contraction along posterior pharyngeal wall

Question 6

Swallowing reflex triggers the involuntary process of…

Answer 6

peristalsis (constrictors are voluntary, but past the larynx muscle becomes smooth)

Question 7

Third phase

Muscular movement?

Answer 7

Cricopharyngeus permits passage of bolus through upper oesophageal sphincter

Tensor and levator veli palatini relax, opening up comms with nasopharynx once more

Hyoid returns to normal position

Epiglottis returns to normal position, opening laryngeal inlet

Contraction wave continues along oesophagus, and the upper oesophageal sphincter closes again