Upper GIT

Question 1

Where is the swallowing centre located?

Answer 1

Reticular formation of the brainstorm - central origin

Question 2

Where are efferent impulses from the swallowing centre distributed?

Answer 2

To the pharynx via nerves from the nucleus ambiguus. The impulses appear to be sequential, so the pharyngeal musculature is activated in a proximal-to-distal manner, allowing the peristaltic contractions to occur.

Question 3

Musculature of the UES

Answer 3

Thickening of circular muscle, - identified anatomically as the cricopharngeal muscle. This muscle is striated

Question 4

What is the velocity of peristaltic contraction moving down the oesophagus?

Answer 4

2-6cm/second

Question 5

How long does it take for a bolus to move down the oesophagus?

Answer 5

10 seconds

Question 6

What is receptive relaxation?

Answer 6

relaxation of the lower oesophageal sphincter, enables an increase in stomach volume without an increase in pressure

Question 7

What nerves control the larynx and pharynx?

Answer 7

Cervical nerves coming from the medulla

Question 8

What nerve controls the oesophagus?

Answer 8

Top half controlled by the 10th cranial (vagus) nerve, that has direct innovation to the longitudinal and circular muscle.
Lower half of the oesophagus, innovation is not direct and the vagus nerve innovates the nerve plexus between the circular muscle layer.

Question 9

What are the 3 regulatory mechanisms of the LES?

Answer 9

• increase neural activity to increase tone
• decrease neural activity to decrease tone
• activate relaxation

Question 10

What is primary peristalsis?

Answer 10

When oesophageal peristalsis proceeded by a pharyngeal phase

Question 11

What is secondary peristalsis?

Answer 11

The absence of both oral and pharyngeal phases. It is elicited when the oesophagus is distended. Secondary peristalsis occurs if the primary contraction fails to empty the oesophagus or when gastric contents reflux into the oesophagus

Question 12

Wha are the type of nerves that coordinate the contractions of the body of the oesophagus?

Answer 12

Somatic motor nerves, arising from the nucleus ambiguus and partly by the visceral motor type, arising from the dorsal motor nucleus.

Question 13

What is the volume of the stomach at rest?

Answer 13

500ml

Question 14

What is the maximum volume of the stomach?

Answer 14

6l

Question 15

Where is the vomiting centre?

Answer 15

lateral reticular formation of the medulla

Question 16

What is the chemoreceptor trigger zone?

Answer 16

Area located on the floor of the fourth ventricle and constitutes the area postrema, a circumventricular organ which is devoid of the blood brain barrier due to which substances such as drugs and toxins carried in the blood can directly reach it. This explains why some drugs cause or stop vomiting. This zone contains dopamine D2, serotonin 5-HT3, opioid, acetylcholine and substance P receptors whose activations results in different pathways, the end result of all of which includes substance P.