6. Motility In The GI Tract

Question 1

How many phases are there in swallowing?

Answer 1

3

Question 2

Is the oral phase of swallowing voluntary or involuntary?

Answer 2

Voluntary

Question 3

What cranial nerve is most important in the oral phase of swallowing?

Answer 3

Hypoglossal (12th cranial nerve)

Question 4

What is the function of the hypoglossal nerve in swallowing?

Answer 4

Oral phase
Provides key motor innervation to the tongue and many of the suprahyoid muscles that stabilise lower jaw
Supports preparation, formation, positioning and transport for the food bolts ready to swallow

Question 5

What receptors lead to the swallowing reflex when activated?

Answer 5

Tactile receptors

Question 6

Where are the tactile receptors located?

Answer 6

Pharynx

Question 7

What is the function of tactile receptors?

Answer 7

Activate afferent nerves which signal to the brainstem

Question 8

What are the key nerves involved in the pharyngeal phase of swallowing?

Answer 8

Glossopharyngeal nerve (9th)
Pharyngeal branches of the vagus (10th)

Question 9

What happens to the soft palate, the epiglottis, the pharynx, and the upper oesophageal sphincter during the pharyngeal phase?

Answer 9

Soft palate rises
Epiglottis closes
Pharynx contracts
Upper oesophageal sphincter relaxes

Question 10

What happens to the upper oesophageal sphincter, the bolus, and the lower oesophageal sphincter during the oesophageal phase?

Answer 10

Upper oesophageal sphincter contracts
Bolus is moved
Lower oesophageal sphincter relaxes

Question 11

What nerves are involved in the oesophageal phase of swallowing?

Answer 11

Glossopharyngeal (9th)
Vagus (10th)

Question 12

What is primary peristalsis?

Answer 12

Upper oesophageal sphincter to lower oesophageal sphincter wave of contraction
Gradient of striated to smooth muscle

Question 13

When does secondary peristalsis occur?

Answer 13

When there is a blockage

Question 14

What is the function of reflex opening and closing of lower oesophageal sphincter and the crural diaphragm?

Answer 14

Reflex opening - food to enter stomach
Reflex closing - prevents gastric content refluxing

Question 15

How does food enter the stomach?

Answer 15

Bolus creates pressure and distension of muscle at bottom of Oesophagus
Stimulates vagal afferent fibres that send signals to the brain stem
Relays signals back to the lower oesophageal sphincter via vagal efferent nerves and to the diaphragm by acetylcholine in efferent phrenic nerves

Question 16

What happens in the corpus region of the stomach when food first arrives?

Answer 16

Relaxes to accommodate the meal

Question 17

What is the second response of the stomach when food arrives?

Answer 17

Fundus - pacemaker zone
Initiates peristaltic contractions that moves down the body of the stomach increasing in frequency and amplitude towards the antrum
Retropulsion occurs

Question 18

What is the name of the process where grinded food is sent back up into the main body of the stomach by the antrum?

Answer 18

Retropulsion

Question 19

What part of the stomach that controls entry from stomach to the small intestine?

Answer 19

Pyloric sphincter

Question 20

Define gastric emptying

Answer 20

Process by which the contents of the stomach (chyme) are moved into the duodenum

Question 21

What are the 4 mechanisms that help accomplish gastric emptying?

Answer 21

Peristaltic waves
Systolic contractions of the antrum
Reduction in size of the stomach
Reflex relaxation of the pyloric sphincter

Question 22

What types of meals delay gastric emptying?

Answer 22

Fat rich
Carb rich
Hypertonic
Acidic
High viscosity
Indigestible

Question 23

What structure is the rate of emptying controlled by?

Answer 23

Duodenum

Question 24

What hormones are released in response to the duodenum receiving food that feedback to gastric emptying?

Answer 24

Cholecystikinin CCK - duodenum
GLP1 - ileum
Peptide YY - ileum

Question 25

What are the pacemakers of the gut?

Answer 25

Interstitial cells of cajal

Question 26

What is the migrating myoelectric complex MMC?

Answer 26

Pattern of electrical activity in the GI tract during fasting - stops when a new meal is eaten

Question 27

What cells secrete HCl?

Answer 27

Parietal cells

Question 28

What cells secrete pepsinogen?

Answer 28

Chief cells

Question 29

What do G cells secrete?

Answer 29

Gastrin

Question 30

What does submucosal plexus do in the stomach?

Answer 30

Regulates gastric secretions and controls blood flow to stomach

Question 31

How does distention by a bolus cause intestinal movement - peristaltic movement?

Answer 31

Distention reflex activates neurones in gut wall that release serotonin (5-HT)
Connects to neurones both behind and infront of the bolus
Behind - ascending contraction orad [towards the mouth]
In front - descending relaxation caudal [towards the tail]

Question 32

What is the name of the process of alternate contraction and relaxation of adjacent segments that causes thorough mixing of food contents in the intestines?

Answer 32

Segmentation

Question 33

Which has stronger peristaltic waves?
The small or large intestine

Answer 33

Large

Question 34

What is the function of segmentation in the large intestine?

Answer 34

Mixes indigestible matter
Helps microbial fermentation of dietary fibre
Facilitates fat and water absorption
Formation of stools

Question 35

What is the defaecation reflex triggered by?

Answer 35

Distention of rectum by faeces or gas

Question 36

What happens to rectum, internal anal spincter, pelvic floor muscles and external anal spincter during defaecation reflex?

Answer 36

Rectum contracts
IAS relaxes
Pelvic floor relaxes
EAS remains contracted

Question 37

What nerve controls defaecation?

Answer 37

Pudenal nerve