Topic 6.2

Question 1

What are the 5 main functions of GI motility?

Answer 1

• Grinding
• Mixing
• Storage
• Propulsion
• Reflux inhibition

Question 2

What is the role of grinding? (3)

Answer 2

Mechanical preparation,
increase surface,
eased propulsion

Question 3

What is the role of mixing? (2)

Answer 3

Renewal of surface

Only nutrients near the wall are absorbed so mix

Question 4

Why do we need storage in GI?

Answer 4

colon stomach : store for optimized digestion, absorption

Question 5

Where do we have reflux inhibition in the GI tract?

Answer 5

In the proximal colon, which shows anti peristalsis

Question 6

Which cells generate the slow waves of GI?

Answer 6

the interstitial cells / cajal cells in the GI wall

Question 7

What is the average slow wave rythm?

Answer 7

3-10 cycles per minute : slow / basal rythm

Question 8

What are the 6 main functions of the oral cavity and oropharynx?

Answer 8

1. mastication
2. swallowing
3. immunological sampling of food for pathogens (Waldeyer lymph ring)
4. Lubrication + tasting of food
5. Vocalization
6. Protection of teeth

Question 9

What is xerostomia?

Answer 9

Dry mouth (can be due to drugs)

Question 10

What are the 3 main parts of the esophagus?

Answer 10

• UES
• Body
• LES / cardia

Question 11

What is the average travel speed down the esophagus?

Answer 11

5cm/s (depends on viscosity)

Question 12

What are the 3 steps of swallowing?

Answer 12

1. drop in neural tone of UES
2. Inhibition of contraction in SM due to NO (relaxation of LES)
3. Rebound contraction to push food downwards

Question 13

What is akalesia?

Answer 13

condition where SM is not relaxing

Question 14

How much food can the stomach store?

Answer 14

up to 1.5L

Question 15

Volume of empty stomach

Answer 15

50mL

Question 16

What is the size of the pylorus opening?

Answer 16

1mm

Question 17

8 roles of the stomach

Answer 17

1. Storage of ingested food
2. Grinding and mixing with the secretion
3. slow and controlled emptying of chyme in duodenum
4. digestion of lipids and proteins
5. limited absorption of lipids
6. regulation of food intake by ghrelin
7. VB12 uptake
8. Chemical barrier for pathogens

Question 18

What are the 3 functional parts of the stomach?

Answer 18

1. proximal part
2. pacemaker zone
3. distal part

Question 19

What is the pacemaker zone of the stomach?

Answer 19

the origin of the contractions which then go down

Question 20

What are the roles of the proximal part of the stomach? (2)

Answer 20

• Storage function

- receptive and adaptative relaxation (steady mb pot)

Question 21

What are the roles of the distal part of the stomach? (2)

Answer 21

• Grinding / mixing

- Propulsion

Question 22

What is retropulsion?

Answer 22

Only done by stomach, pushes contents towards closed pylorus so that it flows backwards and causes grinding

Question 23

Which factors regulate stomach emptying and how?

Answer 23

1. gastric factors : promote emptying

2. duodenal factors : inhibit / limit emptying

Question 24

What is the enterogastric reflex?

Answer 24

stretch receptors in the duodenum sense presence of chyme, and send a signal to the CNS, which will decrease peristalsis using vagus n.

Question 25

What are the 2 gastric factors for regulation of gastric emptying?

Answer 25

- food volume | - release of gastrin from antral mucosa

Question 26

What are the 4 duodenal factors for regulation of gastric emptying?

Answer 26

- Acid : release of secretin - Nutrients, fat sensed by chemoreceptors : release of CCK, GIP - Hypertonicity - Enterogastric reflex

Question 27

6 main functions of the small intestines

Answer 27

1. Mixing, propulsion 2. Digestion and absorption of nutrients 3. Regulation of iron levels 4. Reabsorption of molecules like bile acids 5. Immune functions 6. Symbiosis with bacteria

Question 28

What is segmentation?

Answer 28

renewal of the parts close to the enterocytes for better absorption

Question 29

What regulates segmentation?

Answer 29

enteric nervous system

Question 30

How fast are peristaltic waves?

Answer 30

1cm/sec but really 1cm/min since there's a bunch of other processes

Question 31

What regulates peristalsis?

Answer 31

Gastroenteric reflexes (myenteric plexus) + hormones

Question 32

Which hormones promote peristalsis? (4)

Answer 32

Gastrin, CCK, Insulin, serotonin

Question 33

Which hormones inhibit peristalsis? (2)

Answer 33

Secretin, glucagon

Question 34

What is the law of intestine?

Answer 34

If there is a bolus in the small intestine, there will be contraction in the oral direction and relaxation in the caudal direction

Question 35

Which molecules cause contraction in the oral direction? (2)

Answer 35

Acetylcholine, substance P

Question 36

Which molecules cause relaxation in the caudal direction? (4)

Answer 36

NO, ATP, VIP, PACAP

Question 37

Which drugs can have an impact on serotonin reuptake?

Answer 37

SSRIs : selective serotonin reuptake inhibitor -often for mood disorders)

Question 38

5 main functions of large intestines

Answer 38

1. Propulsion of contents 2. Regulation of H20 and electrolyte balance 3. Storage of fecal matter 4. Immune functions 5. Symbiosis with bacteria

Question 39

Speed of propulsion in large intestines

Answer 39

5-10cm/hour

Question 40

Which kind of movement can we find in the proximal colon?

Answer 40

retropulsive / antiperistalsis

Question 41

Which type of movements can we find in the distal colon?

Answer 41

propulsive movements (mass movements)

Question 42

Which part of the colon does the mixing / segmentation movements?

Answer 42

teniae coli (circular + longitudinal)

Question 43

What regulates the iliocecal valve and sphincter?

Answer 43

Mechano receptors, chemoreceptors, hormones

Question 44

What opens the iliocecal valve? (3)

Answer 44

- distention / irritation of the ileum - gastrin - gastroileal reflex

Question 45

What closes the iliocecal valve?

Answer 45

Distention / irritation of the colon

Question 46

What is the defecation reflex?

Answer 46

stretch of the rectum is reported to S2-S4 spinal chord, leading to relaxation of the internal anal sphincter (SM) thanks to parasympathetic nerve fibers

Question 47

How can the defecation reflex be controlled?

Answer 47

External anal sphincter : SK muscle, can increase tone

Question 48

What is the migrating myoelectric complex?

Answer 48

Motility pattern of stomach and small intestines in bw meals, during which the pylorus is completely open

Question 49

What regulates MMC?

Answer 49

Motilin, which is produced in the duodenum

Question 50

How often does MMC happen?

Answer 50

Roughly every 90 minutes

Question 51

What type of afferents does the vomiting center have?

Answer 51

sympathetic afferents

Question 52

Which process loads the esophagus with content?

Answer 52

The Müller maneuver