Oesophageal Motility and Swallowing

Question 1

What is swallowing/deglutition?

Answer 1

coordinated sequence of events that propels a bolus of food from the mouth to the stomach

Question 2

What are the stages of swallowing?

Answer 2

oral, pharyngeal and oesophageal

Question 3

What occurs during the oral phase of swallowing?

Answer 3

The bolus of food is involuntarily rolled posteriorly into the pharynx

Question 4

Why does the bolus of food move into the pharynx during the oral stage?

Answer 4

This occurs as a result of the upward and backward pressures applied by the tongue against the palate

Question 5

What is the effect of the movement of the bolus of food into the pharynx?

Answer 5

The somatosensory receptors in the pharynx are activated to initiate the involuntary reflex in the medulla

Question 6

Where are the impulses generated by the swallowing receptors in the pharynx sent to?

Answer 6

swallowing centre in the brainstem

Question 7

What occurs at the level of the autonomic pharyngeal muscles due to the impulses generated by the swallowing receptor?

Answer 7

The soft palate is pulled upward to close the posterior nares, which prevents food from entering the pharynx
The pharyngeal folds on each side of the pharynx are pulled medially to approximate each other. This forms a sagittal slit through which the food must pass into the posterior pharynx

Question 8

What changes occur in the larynx during the pharyngeal stage to prevent aspiration?

Answer 8

The vocal cords of the larynx are strongly approximated, and the larynx is pulled upward and the anteriorly by the neck muscles.
The epiglottis swings backwards over the opening of the larynx.
Altogether, food is prevented from entering the pharynx

Question 9

What is inhibited during the pharyngeal phase of swallowing?

Answer 9

The respiration centre in the medulla, in order to inhibit breathing

Question 10

Which areas of the posterior mouth and pharynx are most sensitive for initiating the pharyngeal stage of swallowing?

Answer 10

A ring around the pharyngeal opening, including the tonsillar pillars

Question 11

Where does the sensory impulses during the pharyngeal stage go to?

Answer 11

nucleus tractus solitarius in the medulla oblongata via the trigeminal and glossopharyngeal nerves

Question 12

What sends motor impulses during the pharyngeal stage of swallowing?

Answer 12

trigeminal n.
glossopharyngeal n.
vaugs n.
hypoglossal n.

Question 13

How does the musculature and control of muscle differ between the upper 1/3 and lower 2/3 of the oesophagus?

Answer 13

Upper 1/3 = skeletal, controlled by the glossopharyngeal and vagus nerves
Lower 2/3 = smooth, controlled by the vagus nerve

Question 14

What is primary peristalsis?

Answer 14

A continuation of pharyngeal peristalsis, that is controlled by the swallowing reflex and lasts 8-10 seconds

Question 15

When does secondary peristalsis occur?

Answer 15

When primary peristalsis fails to move all the food toward the stomach; initiated by distention of the oesophagus by the food

Question 16

What occurs when the oesophageal peristaltic waves reach the stomach?

Answer 16

They cause inhibition of the myenteric neurons to relax the stomach to receive food

Question 17

What are the functions of the upper oesophageal sphincter?

Answer 17

Prevents entry of air into the oesophagus
Relaxes during swallowing for 1 second to allow food to be forced through

Question 18

When does the lower oesophageal sphincter open?

Answer 18

It opens with initiation of oesophageal peristalsis by impulses from the vagus nerve

Question 19

What stimulates the lower oesophageal sphincter to close/contract?

Answer 19

During swallowing vagal cholinergic impulses maintain the contracture of the lower oesophageal sphincter
Stimulation of sympathetic nerves to the sphincter contract it
Gastrin stimulates contraction

Question 20

What stimulates the lower oesophageal sphincter to relax?

Answer 20

During swallowing, different impulses from the vagus nerve exert an inhibitory effect on the sphincter, causing it to relax
Secretin and cholescystokinin stimulate relaxation