Topic 6.3

Question 1

3 types of secretors in the GI

Answer 1

• Exocrine glands (pancreas, salivary)
• Gland formed by the gut wall itself (Bruner, Lieb)
• Intestinal mucosa

Question 2

2 main functions of GI secretion

Answer 2

Protection, and promotion of digestion + absorption

Question 3

What are the 2 types of GI secretion?

Answer 3

Organic, inorganic

Question 4

What are secretagogues?

Answer 4

Ligands which can act on secretory cells. Can be either endocrine or paracrine.

Question 5

How much secretion / day?

Answer 5

9-10L day / secretion

Question 6

Daily production of saliva

Answer 6

800-1500mL / day

Question 7

7 main functions of saliva

Answer 7

1. Disrupts the food into smaller particles
2. Lubrication for swallowing and speaking
3. Initiation of starch and lipid (kids) digestion
4. Cleansing function
5. Antimicrobial effect
6. Neutralization of gastric content
7. Calcium binding proteins for teeth

Question 8

How does the saliva have an antimicrobial effect?

Answer 8

Contains IgA and lysozymes

Question 9

What are the major salivary glands? (3)

Answer 9

Parotid, sublingual, submandibular

Question 10

What are the minor salivary glands? (3)

Answer 10

Tongue, lips, palate

Question 11

What is the general structure of the salivary glands?

Answer 11

Tubuloalveolar

Question 12

What are the 2 types of acinar cells and their difference?

Answer 12

• Mucous : produce mucin

- Serous : have zymogen granules (amylase and lipase)

Question 13

What type of gland is parotid?

Answer 13

Mostly serous

Question 14

What type of gland is sublingual?

Answer 14

Mainly mucous / mixed

Question 15

What type of gland is submandibular?

Answer 15

Mixed

Question 16

What type of gland is buccal?

Answer 16

Mucous

Question 17

4 proteins produced in the acinar cells?

Answer 17

• Amylase
• Ig
• Mucin
• R protein (haptocorin)

Question 18

What is haptocorin useful for?

Answer 18

B12 absorption : protects it from acidity of the stomach

Question 19

how is the primary secretion compared to the plasma?

Answer 19

Isoosmotic, with similar electrolyte concentration to blood plasma

Question 20

What type of epithelium is the acinar epithelium?

Answer 20

leaky epithelium

Question 21

What inhibits ENaC?

Answer 21

amiloride

Question 22

What upregulates ENaC?

Answer 22

Aldosterone

Question 23

How is the resulting saliva?

Answer 23

Hypoosmotic, and alkaline compared to its surroundings

Question 24

How is salivary secretion regulated?

Answer 24

Mostly parasympathetic, neural regulation

Question 25

What is VIP coupled to and what does it result in?

Answer 25

Gs coupled, causes "atropine resistant" vasodilation, which increases secretion

Question 26

What is Ach couples to and what does it result in?

Answer 26

Gq coupled (M3) on acinar cells, causes exocytosis and constriction of acinar cells, which increases secretion

Question 27

What effect does the sympathetic system have on salivary secretion? (2)

Answer 27

- B2 : increases mucin secretion | - A1 : constricts vessels

Question 28

What is the external way of salivary secretion?

Answer 28

Unconditioned stimuli activates CN, for example : seeing food, smell...

Question 29

What type of cells are in the midline of the gastric mucosa?

Answer 29

proliferative cells (regenerate the mucosa)

Question 30

What do surface epithelial cells produce? (2)

Answer 30

mucin, bicarbonate

Question 31

What do parietal cells secrete? (2)

Answer 31

the gastric acid + intrinsic factor through exocytosis

Question 32

What do chief cells secrete?

Answer 32

digestive enzymes

Question 33

Which cells of the gastric mucosa can be found everywhere in the stomach?

Answer 33

the surface epithelial cells

Question 34

What is the daily production of gastric juice?

Answer 34

1-1.5L / day

Question 35

How is the gastric juice osmotically?

Answer 35

isoosmotic

Question 36

What are the 4 main constituents of gastric juice?

Answer 36

Water, electrolytes (H, Cl), bicarbonate, proteins (mucin, digestive enzymes)

Question 37

What are the 3 functional regions of the stomach?

Answer 37

- Cardia / LES - Fundus / body - Antrum / pylorus

Question 38

Which is the only region of the stomach to produce gastric juice / acid?

Answer 38

The fundus / body, the rest only secrete mucin and bicarbonate

Question 39

What is the role of the cardia / LES?

Answer 39

prevent reflux, entry of food

Question 40

What is the role of the fundus / body?

Answer 40

reservoir + secretion of gastric juice

Question 41

What is the role of the antrum / pylorus?

Answer 41

mixing, grinding, regulation of emptying

Question 42

Which cells secrete the intrinsic factor?

Answer 42

parietal cells

Question 43

How do parietal cells increase their surface and energy?

Answer 43

With the canaliculi and the mitochondria

Question 44

What are the 2 forms of the parietal cell?

Answer 44

- Resting / inactive | - Active / secreting (has canalicul)

Question 45

Which drugs can inhibit the K+ / H+ pump? (2)

Answer 45

omeprazol, pantoprazol

Question 46

What is the H+ source for gastric acid?

Answer 46

Parietal cell metabolism

Question 47

How is the H+ gradient in parietal cell / lumen?

Answer 47

The gradient is a million-fold : 10^6 : from pH = 7.2 to pH = 1-2

Question 48

What is the most important regulator of gastric acid secretion?

Answer 48

parasympathetic nervous system through vagal nerve stimulation

Question 49

What are the 6 ways of activating G cells?

Answer 49

1. Ach 2. GRP (gastrin releasing peptide) : para sympathetic NT 3. Mechanical stimuli : wall tension 4. Alcohol, soda, cola 5. Helicobacter pilori 6. Sympathetic system : B2 receptor

Question 50

What is the G cell inhibitor?

Answer 50

Somatostatin

Question 51

How is the release of somatostatin triggered?

Answer 51

If GA secretion is too high, pH is too low, which activates the D cells - which produces somatostatin

Question 52

What type of receptor is somatostatin coupled to?

Answer 52

Gi receptor

Question 53

ON which cells can somatostatin act?

Answer 53

On g cells mostly, or directly on parietal cells

Question 54

On which cells can gastrin act to regulate GA secretion?

Answer 54

On parietal cell directly or on ECL cells, which then release histamine to the parietal cells

Question 55

What are the 2 phases of GA secretion?

Answer 55

``` Cephalic phase (smelling, tasting) Gastric phase (presence of protein breakdown product) ```

Question 56

Which molecule can decrease GA secretion (on top of somatostatin)

Answer 56

prostaglandins

Question 57

What produces prostaglandins?

Answer 57

COX enzymes

Question 58

How do prostaglandins decrease GA?

Answer 58

Gi signaling, reduce cAMP signal and decrease secretion

Question 59

How does GA composition change based on the rate of secretion?

Answer 59

- Basal secretion : ++ NaCl, low H+ | - High secretion : ++ H+ and Cl

Question 60

What can we use to measure the H+ content of GA?

Answer 60

- BAO (basal acid output) | - PAO (peak acid output)

Question 61

What is the basal acid output?

Answer 61

1.5 - 2.5 mmol H+ / hour

Question 62

What is the peak acid output?

Answer 62

Women : 25 mmol H+ / hour | Men : 35 mmol H+ / hour

Question 63

What protects the gastric mucosa from high acidity?

Answer 63

2mm sticky mucin layer produced by surface epithelial cells

Question 64

What can regulate Chief cell secretion? (4)

Answer 64

- Acetylcholine (vagus stimulation after meal) | - Gastrin, secretin, CCK