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GI > PHYS: Pancreatic Secretion > Flashcards

PHYS: Pancreatic Secretion Flashcards

1
Q

What are the two components of exocrine pancreas secretion?

A

Aqueous component

Enzyme component

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2
Q

What is a characteristic of the aqueous component of the pancreatic secretion?

A

rich in HCO3-

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3
Q

What is the function of the aqueous component of the pancreatic secretion?

A

functions to neutralize the H+ delivered to the duodenum from the stomach to achieve optimal pH for pancreatic enzyme activation

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4
Q

What is the function of the enzyme component of the pancreatic secretion?

A

functions to digest carbohydrates, proteins and lipids into absorbable molecules.

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5
Q

How much of the pancreas is considered to be “exocrine”?

A

around 90%

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6
Q

What is the name of the blind end of the branching pancreatic ducts?

A

acinus

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7
Q

What is the acinus lined by?

A

acinar cells

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8
Q

What is the major component of the exocrine pancreas (80%)?

A

acinar cells

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9
Q

What is the role of acinar cells?

A

secrete the enzymatic portion of the pancreatic secretion

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10
Q

What cell type is located at the connection between the acinus and the duct?

A

centroacinar cells

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11
Q

What is the role of the centroacinar cells?

A

secrete the aqueous portion of the pancreatic secretion (along with ductal cells)

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12
Q

What is located at the apical membrane of acinar cells?

A

multiple zymogen granules (full of pancreatic enzymes)

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13
Q

What is the source of sympathetic innervation to the exocrine pancreas?

A

postganglionic nerves from celiac and superior mesenteric plexuses

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14
Q

What is the role of sympathetic innervation to the exocrine pancreas?

A

inhibits pancreatic secretion

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15
Q

What is the source of parasympathetic innervation to the exocrine pancreas?

A

provided by the vagus nerve—synapse in the enteric nervous system, and postganglionic fibers synapse on exocrine pancreas

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16
Q

What is the role of parasympathetic innervation to the exocrine pancreas?

A

stimulates pancreatic secretion

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17
Q

Describe the aqueous component of pancreatic secretions.

A

isotonic solution of Na+, Cl-, K+, and HCO3-.

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18
Q

Flow rate of aqueous pancreatic secretion changes the concentrations of which components?

A

Cl-

Bicarbonate

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19
Q

True or false: the higher the flow rate, the lower the bicarbonate.

A

FALSE: higher the flow rate, the higher the bicarb

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20
Q

What is the role of carbonic anhydrase in the production of aqueous pancreatic secretion?

A

Carbonic anhydrase combines H2O and CO2 in the pancreatic ductal cell to form bicarbonate + H+.

21
Q

How does the bicarbonate made by carbonic anhydrase get into the pancreatic juice?

A

This bicarbonate is secreted into pancreatic juice by a HCO3-/Cl- exchanger in the apical membrane

22
Q

How does the H+made by carbonic anhydrase get into the blood?

A

The H+ is secreted into the blood via the Na+/H+ exchanger in the basolateral membrane. (along the concentration gradient set up by Na+/K+ ATPase)

23
Q

How does Cl- get into the pancreatic juice?

A

CF membrane regulator

24
Q

What alters the action of the CF membrane regulator?

A

secretion increases cAMP and leads to Cl- release

25
Q

What is the composition of the enzymatic poriton of the pancreatic secretion?

A

amylase (carb digestion)
lipase (lipid digestion)
proteases

26
Q

How do pancreatic enzymes get placed into zymogen granules?

A
  1. Proteins synthesized in the rough ER of the acinar cells.
  2. Proteins in the ER lumen bud off as transitional elements
  3. TEs fuse on to the Golgi complex and proteins are altered
  4. Budding off of Golgi as condensing vacuoles (Cl- and water pumped out to increase concentration of enzymes in the granules)
  5. Zymogen granule
27
Q

What is the stimulus for fusion of zymogen granules and exocytosis of enzymes into the lumen?

A

Ach stimulus→ Ca2+ triggers fusion and exocytosis of enzymes from zymogen granules into the lumen

28
Q

What stimulates the production of the aqueous portion of pancreatic secretion?

A

stimulated by arrival of H+ in the duodenum

29
Q

What stimulates the production of the enzymatic portion of pancreatic secretion?

A

products of digestion (small peptides, AAs, FAs)

30
Q

List the 3 phases of pancreatic secretion and their relative contributions to the process.

A
  • Cephalic phase (~20%)
  • Gastric phase
  • Intestinal phase (~80%)
31
Q

What type of secretion is produced (mainly) by each phase of pancreatic secretion?

A
  • Cephalic phase (enzymatic)
  • Gastric phase (enzymatic)
  • Intestinal phase (enzymatic AND aqueous)
32
Q

What stimulates the cephalic phase?

A

smell, taste, and conditioning are the stimuli and act through vagus nerve

33
Q

What stimulates the gastric phase?

A

distention of the stomach is the stimuli and acts through the vagus nerve

34
Q

What type of receptors are present on acinar cells in the pancreas?

A

Ach

35
Q

How does the intestinal phase of pancreatic secretion lead to the release of enzymatic secretions?

A
  • I cells are stimulated (by presence of AAs, small peptides, and FAs in the stomach) to release CCK→ causes a vagovagal reflex that releases Ach.
  • Ach binds to muscarinic receptors on acinar cells→stimulates secretion!
36
Q

What type of receptors are present on ductal cells in the pancreas?

A

secretin

37
Q

How does the intestinal phase of pancreatic secretion lead to the release of aqueous secretions?

A
  • Secretin is released by S cells in response to H+ in the lumen of the intestine
  • In order to neutralize this acid, secretin stimulates the release of aqueous HCO3- from the ductal cells.
38
Q

What pH is adequate for S cells to get the signal that chyme has arrived from the stomach?

A

3-4.5

39
Q

What can also lead to secretin release (other than pH of 3-4.5)?

A

increase the AMOUNT of titratable acid (increased exposure to higher volumes of acid–not necessarily a higher pH)

40
Q

The presence of what amino acid leads to potentiation of the secretin effect on bicarbonate release (leads to peak release of HCO3-)?

A

phenylalanine

41
Q

What is an example of potentiation in the production of enzymatic secretion from the pancreas?

A

Secretin and Ach act on two different receptors to stimulate two different pathways that lead to elevated calcium levels and enzyme release from the acinar cells.

42
Q

What is the term for a decreased volume of pancreatic juice and a decrease in level of bicarbonate in the pancreatic juice?

A

pancreatitis

43
Q

What are the two major factors that lead to pancreatitis?

A
  • Alcoholism

- Blockage of pancreatic duct by gallstones

44
Q

How does blocking pancreatic duct lead to pancreatitis?

A

enzymes back up and trypsinogen is converted to trypsin→ activates other enzymes→ autodegredation of exocrine pancreas

45
Q

What is the condition characterized by extreme malnutrition with a decreased volume of pancreatic juice (decreased bicarbonate AND enzymes)?

A

Kwashiorkor

46
Q

What causes Kwashiorkor?

A

protein synthesis is decreased along with patient being malnourished

47
Q

What is the autosomal recessive condition with lack of Cl- conductance in the apical membrane (faulty synthesis of channel or inability of the cell to put chennel in membrane)?

A

Cystic fibrosis

48
Q

What effect does CF have on pancreatic secretion?

A

decreased volume of pancreatic juice (decreased bicarbonate AND enzymes)

49
Q

What is a common symptom between CF and Kwashiorkor?

A

steatorrhea (no enzymes to break down fat)

GI (21 decks)

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