Salivary and Gastric Secretions

Question 1

How are proteins (enzymes) secreted?

Answer 1

Exocytosis in response to neuroendocrines

Question 2

How are fluids (electrolytes and water) secreted?

Answer 2

Osmotic pressure in the lumen

Question 3

Function of salivary secretions?

Answer 3

1. lubrication (help swallowing and speech)
2. protection
3. digestion

Question 4

What does lysozyme do?

Answer 4

Effective against gram positive bacteria

Question 5

What does lactoferrin do?

Answer 5

Effective against gram negative bacteria

Question 6

Where is lingual lipase activated?

Answer 6

In the stomach by acid

Question 7

Why are digestive enzymes in saliva necessary?

Answer 7

(1) if a baby does not have mother who can provide breast milk, someone can chew food and feed it to baby which now has secretory IgA
(2) if an adult has pancreatic insufficiency (salivary enzymes can compensate)

Question 8

Characteristics of saliva

Answer 8

(1) concentrations of electrolytes vary with rate of secretion
(2) always hypotonic
(3) always lower in sodium and chloride than plasma
(4) always higher in potassium than plasma
(5) rich in bicabonate

Question 9

What are the two cells in a salivary duct?

Answer 9

(1) acinar cells

(2) ductal cells

Question 10

Fluid and Ions secreted by acinar ells

Answer 10

H2O, HCO3-, Na+, K+, Cl-

Question 11

Ions secreted by ductal cells? Ions absorbed by ductal cells?

Answer 11

absorbed: Cl-, Na+
secreted: HCO3-, K+, H2O

Question 12

stimulation of salivary nucleus of the medulla?

Answer 12

Conditioned reflex, smell, taste, pressure, nausea

Question 13

inhibtion of salivary nucleus of the medulla?

Answer 13

fatigue, lack of sleep, fear, dehydration

Question 14

What myoepithelial cells?

Answer 14

Epithelial cells that acquired muscle cell characteristics

Question 15

What nerves do salivary nucleusof the medulla stimulate?

Answer 15

(1) Sympathetics T1-T3 -> Superior Cervical Ganglion -> NE

2) Parasympathetics CN IX, X and FN VII -> Ach, VIP (more stimulated than sympathetic

Question 16

Two components of gastric secretion?

Answer 16

(1) oxyntic component

(2) non-oxyntic component

Question 17

What is the oxyntic component of gastric secretion?

Answer 17

H+, Cl-, K+, IF (parietal cells)

- highly stimulated by feeding

Question 18

What is the non-oxyntic component of gastric secretion?

Answer 18

mucus, Na+, HCO3- (mucous cells), pepsinogen (chief cells), diffused interstitial fluids (Cl-, H2O)
- rate remains relatively constant (major component at resting, but is highly diluted by the oxyntic component upon feeding)

Question 19

A. Severe vomiting result in loss in what?

B. Extensive loss of saliva result in what?

Answer 19

A. loss of gastric acid, H+ and Cl-

B. loss of plasma K+

Question 20

Functions of gastric secretions?

Answer 20

(1) digestion
(2) aiding absorption
(3) protection

Question 21

How does gastric secretion aid digestion?

Answer 21

• acidic pH activated pepsinogen and lipases (lingual)

- HCL denatures proteins for optimal digestion by pepsin

Question 22

How does gastric secretion aid absorption?

Answer 22

• HCL solubilizes minerals

- Intrinsic factor is required for the absorption of Vit. B12

Question 23

How does gastric secretion protect lumen?

Answer 23

• HCl inactivates microbes

- Mucus, HCO3-, and Cl- provide containment for H+

Question 24

How does stimulation of parietal cell change its morphology?

Answer 24

In response to stimulation, tubulovesicle rich in H+ pumps in resting parietal cell fuse with intracellular canaliculi open to the lumen of the gastric pit to secrete H+

Question 25

What is an alkaline tide?

Answer 25

pH increase in the gastric or portal vein because HCO3- absorption in portal vein is coupled to H+ secretion in lumen

Question 26

When does the alkaline tide occur?

Answer 26

(1) after a major meal: postprandial alkaline tide (physiological)
(2) severe vomiting: sustained alkaline tide (metabolic alkalosis)

Question 27

What stimulates acid secretion?

Answer 27

PS, gastrin, histamine

Question 28

How is HCl contained?

Answer 28

(1) Cl- current
(2) muscosal barrier (mucus gel and HCO3-)
(3) cytoprotection by prostagladins

Question 29

What do prostagladins do?

Answer 29

(1) inhibition of HCL secretion

(2) stimulation of mucus gel and HCO3- production

Question 30

What inhibits prostagladins?

Answer 30

Non-steroid anti-inflammatory drugs (NSAID)