Swallowing

Question 1

how is swallowing initiated

Answer 1

Initiated when pressure receptors in the walls of the pharynx are stimulated by food or drink, forced into the rear of the mouth by the tongue

Question 2

innervation of nasopharynx

Answer 2

Maxillary nerve (V2 (second branch of trigeminal nerve (V))

Question 3

innervation of oropharynx

Answer 3

Glossopharyngeal nerve (IX)

Question 4

innervation of Laryngopharynx

Answer 4

Vagus nerve (X)

Question 5

Stage one of swallowing (voluntary)

Answer 5

• Food is compressed agains the roof of the mouth and pushed towards the oropharynx by the action of the tongue
• The buccinator & supra hyoid muscles manipulate food during chewing. They also elevate the hyoid boneand flatten the floor of the mouth

Question 6

Stage two of swallowing (involuntary)

Answer 6

• The nasopharynx is closed off by the soft palate via the action of the muscles of the palate which tense & elevate it - helping to form the bolus of food
• The pharynx is also shortened & widened (using longitudinal muscles)by the elevation of the hyoid bone via the actions of the muscles of the floor of the palate which depress (lower) the mandible if the hyoid bone is fixed or elevate (raise) the hyoid bone & larynx if the mandibles is fixed

Question 7

Stage two of swallowing (involuntary)

-Impulses from the swallowing centre do what

Answer 7

-Impulses from the swallowing centreinhibit respiration, raise the larynx (as mentioned above) and close the glottis (the area around the vocal cords and the space between them) - keeping food from entering the trachea

Question 8

Stage two of swallowing (involuntary)

-As the tongue forces the food farther back what happens

Answer 8

-As the tongue forces the food farther backinto the pharynx the food tilts the epiglottis backward to cover the closed glottis - this prevents aspiration of food - a dangerous situation where food travels down the trachea and can cause chokingor regurgitated stomach contents are allowed into the lungs causing damage

Question 9

Stage 3 - Involuntary:

Answer 9

• The sequential contraction of the constrictor muscles (circular) followed by the depression (return) of the hyoid bone and pharynx
• Pharyngeal constrictor muscles - 3overlapping muscles that form the posterior & lateral sides of the pharynx - innervated by vagus (X). They contract sequentially from above down to drive the bolus into the oesophagus

Question 10

Stage 3 - Involuntary

Depression of the hyoid bone and pharynx is carried out by

Answer 10

Depression of the hyoid bone and pharynx is carried out by the infra hyoid muscle of the neck - they fix the hyoid bone enabling the opening of the mouth. They also depress the hyoid bone and larynx

Question 11

What type of muscle surrounds what part of the oesophagus

Answer 11

• Skeletal muscle surrounds the upper third of the oesophagus
• Smooth muscle surround the lower two-thirds of the oesophagus

Question 12

The luminal pressure in the pharynx at the opening to the oesophagus is equal to the atmospheric pressure and the pressure at the opposite end of the oesophagusin the stomach is slightly greater than atmospheric pressure. Thus these pressure differences tend to

Answer 12

tend to force both air from above and gastric contents from below into the oesophagus - however this does not occur due to the presence of sphincter muscles at both ends of the oesophagus.

Question 13

what is the upper oesophageal sphincter

Answer 13

A ring of skeletal muscle surround the oesophagus just below the pharynx

Question 14

what is the lower oesophageal sphincter

Answer 14

A ring of smooth muscle surround the oesophagus in the last portion of the oesophagus

Question 15

Before food can enter the oesophagus what happens

Answer 15

the upper oesophageal sphincterrelaxes - immediately after the food has passed through the sphincter closes, the glottis opens and breathing resumes

Question 16

Once in the oesophagus how does food move towards the stomach

Answer 16

Once in the oesophagus, the food moves towards the stomach by a progressive wave of muscle contractions that proceed along the oesophagus, compressing the lumen and forcing the food ahead - these are peristaltic waves

Question 17

How long does peristaltic wave take to reach the stomach

Answer 17

One oesophageal peristaltic wave takes 9 seconds to reach the stomach

Question 18

What does the lower oesophageal sphincter do during swallowing

Answer 18

The lower oesophageal sphincter opens and remains relaxed throughout the process of swallowing, allowing the arriving food to enter the stomach

Question 19

Reflex arc of the gag reflex is where

Answer 19

between the glossopharyngeal (IX) and the vagus (X) nerves

Question 20

What causes vomiting in the gag reflex

Answer 20

vomiting cause by irritationof the oropharynx - the back of the tongue

Question 21

What is the gag reflex

Answer 21

The reflex elevation of the pharynx