41 Salivary and Exocrine pancreatic physiology

Question 1

Which 2 enzymes are involved when food is digested by salivary secretion?

Answer 1

1. Alpha-amylase

2. Lingual lipase

Question 2

List 3 functions of salivary secretion.

Answer 2

• Digestion
• Solubilization of food for taste bud
• Lubrication of food for swallowing
• Cleaning of buccal mucosa and teeth (Xerostomia: dry mouth)
• Protection of antibacterial actions
• Facilitation of speech

Question 3

What are the 3 salivary glands? What cells do they contain respectively?

Answer 3

1. Parotid cells (serous cells only)
2. Sublingual cells (mostly mucous cells)
3. Submandibular cells (mixed)

Question 4

What is the functional unit of salivary glands?

Answer 4

Salivon

Question 5

A salivon can be divided into 3 parts: the acinus, the intercalated duct and the striated duct.
What cells are present in each part and what are their respective functions?

Answer 5

Acinus: acinar cells, myoepithelial cells; secrete initial salivary secretion

Intercalated duct: myoepithelial cells; they are contractile cells that control saliva flow via parasympathetic nerves

Striated duct: Ductal cells; secrete and modify inorganic composition (Na+, Cl-)

Question 6

Regulation of salivary secretion is exclusively under:
A. Hormonal control
B. Endocrine control
C. Neural control

Answer 6

C

Question 7

True or False:

Sympathetic nerves exert major stimulatory effect in salivary regulation

Answer 7

False.
Should be parasympathetic as major,
BUT sympathetic also stimulates secretion!

Question 8

In regulation of salivary secretion, aldosterone and ADH

A. do not play any role
B. Modify ionic content of saliva by decreasing Na+ and increasing K+
C. regulate secretion of saliva

Answer 8

B only

Question 9

Which of the following is not a stimulatory factor of salivary secretion?

1. Chewing
2. Conditioned reflex
3. Dehydration
4. Nausea
5. Smell

Answer 9

3. will secrete less when there is dehydration

for nausea, saliva is secreted to dilute the gastric juice during vomiting to prevent damage to mouth and esophagus

Question 10

Which of the following is/are inhibitory factor(s) of salivary secretion?

1. Sleep
2. Fatigue
3. Fear
4. Dehydration

Answer 10

All of the above

Question 11

Which secondary messenger is activated when there is parasympathetic stimulation in salivary secretion?
What receptors is being activated?

Answer 11

IP3 > Ca2+

Muscarinic receptors on the salivary gland are stimulated by the glossopharyngeal nerve and facial nerve.

Question 12

Which of the followings are glandular activities stimulated by parasympathetic nerves?

1. Secretion of saliva
2. Myoepithelial cells contraction
3. Vasoconstriction
4. Growth
5. Metabolism

Answer 12

All except 3

Vasodilation is stimulated

Question 13

In sympathetic stimulation in salivary secretion, what neural substance is released to activate what receptors?

Answer 13

Noradrenaline acts on adrenergic receptors of salivary gland.

Question 14

In pancreatic exocrine secretion,
A. Acinar cells is the majority of cells compared to duct cells.

B. Acinar cell > Ductal epithelium. In which Intercellular canaliculi > Intralobular duct > Extralobular duct

C. Pancreatic duct joins with the common bile duct after entering the duodenum via relaxation of Sphincter of Oddi

Answer 14

A and B ony

A. Acinar cells (82%) and duct cells (3.9%)

C. Pancreatic duct joins with the common bile duct before entering the duodenum via relaxation of Sphincter of Oddi

Question 15

Pancreatic exocrine secretion consists of aqueous and enzymatic component. What are they made up of respectively?

Answer 15

Aqueous component: by ductal epithelium with Na+HCO3-

Enzymatic component: by acinar cells

Question 16

The aqueous component of pancreatic consists of the ductal epithelium with Na+ HCO3- which serves to:
(2 functions)

Answer 16

1. Neutralize gastric chyme to prevent the injury to the duodenal mucosa
2. Provide optimal pH for pancreatic digestive juices

Question 17

True or false: Proteins by the acinar cells are active before being secreted into the duodenum.

Answer 17

False. All proteins are in precursor form unless it is released into the duodenum

Question 18

Cl- release depends on _________, which is affected by ________ secreted by endocrine ___ cells, causing cAMP to increase and Cl- to come out.

Answer 18

CFTR Cystic fibrosis transmembrane conductance regulator

Secretin; S cells

Question 19

The enzyme ________ facilitates conversion of water to OH- and H+, thus OH- can enter the lumen via Cl-/HCO3- exchanger (1 HCO3- out, 1 Cl- in)

Answer 19

Carbonic anhydrase

Question 20

What is cystic fibrosis?

Answer 20

• Defective CFTR channel which cannot be opened
• Blocked acini ducts with thick and viscous mucous
• Tissue destruction/fibrosis
• Pancreatic exocrine insufficiency

Question 21

What are the 3 basic factors stimulating pancreatic secretion?
What are their actions respectively?

Answer 21

a. Acetylcholine; stimulate acinar cells to secrete enzymatic component

b. CCK; response to fat,
stimulate acinar cells to secrete enzymatic component

c. Secretin; response to acidic food, secrete aqueous component (primary stimulus of Na+ HCO3- secretion)

Question 22

What are the 3 phases of pancreatic secretion ?(different from 40 gastric!)

Briefly describe each phase.

Answer 22

1. Cephalic phase (20%, neural only)

• Stimulus: vagus nerve and ENS
• Acetylcholine: M3 receptors on duct cells and acinar cells
• Stimulate enzymatic secretion mainly.

2. Gastric phase (5%)

3. Intestinal phase (75%)
Hormonal and neural;
Hormonal is predominant:
- Fat > I cells > CCK > Duct cells
- H+ > S cells > secretin > acinar cells;

Neural is minor:

• Acetylcholine > M3 receptor > duct cells (short reflex)
• on acinar cells: long reflex

Question 23

CCK and acetylcholine
A. is responsible for enzymatic secretin
B. is responsible for aqueous secretion
C. can multiply the aqueous secreting function of secretin

Answer 23

A and C only

B: no, only secretin does it