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Physiology > Exocrine Pancreas > Flashcards

Exocrine Pancreas Flashcards

1
Q

The pancreas is _____

A

Bi-lobed

  • body: pylorus
  • right lobe: mesoduodenum, ventral to right kidney, apposition to duodenum
  • left lobe: caudal to stomach and liver
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2
Q

Exocrine functions of pancreas

A
  • enzymes secreted into a duct
  • ducts lead to external environment
  • digestive enzymes
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3
Q

Endocrine functions of pancreas

A
  • hormones secreted into the blood
  • function at distant sites, not on the cells that secreted them
  • insulin
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4
Q

Exocrine histologic anatomy

A
  • acini: digestive enzymes

- ducts: bicarbonate

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5
Q

Endocrine histologic anatomy

A

Islets of Langerhans

  • alpha cells: glucagon
  • beta cells: insulin
  • delta cells: somatostatin/gastrin
  • PP cell: pancreatic polypeptide
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6
Q

Acini are arranged as a ______

A

Cluster of grapes

  • lead out to the pancreatic or accessory duct
  • bicarb is made within the ducts
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7
Q

Sympathetic innervation

A

Inhibitory!!!

  • celiac plexus
  • mesenteric plexus
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8
Q

Parasympathetic innervation

A

Stimulatory!!

  • branches of vagus or other cholinergic nerves in the enteric nervous system
  • terminate in acini (exocrine) or islets (endocrine)
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9
Q

In dogs, the bile duct enters _______

A

Major duodenal papilla

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10
Q

Accessory pancreatic duct (dogs)

A

Most important

  • enters minor duodenal papilla
  • separate from bile duct
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11
Q

Pancreatic duct (dogs)

A

Less important

  • may not be present
  • empties into major duodenal papilla separate from bile duct
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12
Q

Most pancreatic secretions in the dog go into the _______

A

Accessory pancreatic duct

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13
Q

Pancreatic duct (cats)

A

Most important

- enters major duodenal papilla –> after joining with the common bile duct first

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14
Q

Accessory pancreatic duct (cats)

A

Only present in 20% of cats

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15
Q

Triaditis

A

Common in cats

  • inflammation affects the liver, common bile duct, and the gallbladder = back up of bile flow
  • pancreatitis can make cats yellow, liver complications are secondary
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16
Q

What are the 3 functions of the exocrine pancreas?

A
  • release of mostly inactive digestive enzymes
  • neutralization of gastric acid
  • secretion of intrinsic factor
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17
Q

Intrinsic factor

A

Secreted by parietal cells in humans

- facilitates B12 absorption in the distal small intestine

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18
Q

Lack of B12

A

Pernicious anemia in people

- diarrhea in dogs and cats

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19
Q

Bicarbonate secretion

A

Released by ductal cells

  • neutralizes gastric acid
  • intestinal mucosa protection
  • increased pH necessary for enzyme activity
  • reaches 5 times the plasma bicarb concentration
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20
Q

Enzymes are only functional at a _______

A

Higher pH

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21
Q

What are the 3 functions of pancreatic enzymes?

A
  • protein digestion
  • carbohydrate digestion
  • fat digestion
22
Q

Protein digestion

A

Zymogens

  • trypsinogen
  • chymotrypsinogen
  • procarboxypeptidase
23
Q

Carbohydrate digestion

A

Pancreatic amylase

24
Q

Fat digestion

A
  • pancreatic amylase
  • cholesterol esterase
  • phospholipase
25
Q

Proteolytic enzymes following activation

A
  • trypsin
  • chymotrypsin: both split whole proteins or partially-digested peptides into smaller peptides
  • carboxypeptidase: splits some peptides into individual amino acids
26
Q

Pancreatic amylase

A

Hydrolyzes starches

  • glycogen and others
  • into di- or trisaccharides
27
Q

Pancreatic lipase

A

Neutral fat –> FA + monoglycerides

  • cholesterol esterase: hydrolysis of cholesterol esters
  • phospholipase: separates FAs from phospholipids
28
Q

Protection from auto-digestion

A
  • zymogen synthesis (proteases)
  • segregation into vacuoles in acinar cell (separate from lysosomes)
  • trypsin inhibitors in cytoplasm (and some are circulating)
  • sphincter at pancreatic duct (inhibits reflux)
29
Q

Zymogen

A

Prozymes (inactive enzyme)

  • trypsinogen
  • chymotrypsinogen
  • activation required
30
Q

Zymogens are synthesized by _______

A

Ribosomes

- formation and storage in vesicles

31
Q

Zymogen stimulation of the cell

A

Fusion of granules to plasma membrane –> release of content into glandular lumen –> secretion into duodenum

32
Q

Zymogens are activated in the ______

A

Duodenum

- enterokinase (brush border enzyme) –> activates trypsinogen into trypsin

33
Q

Trypsin activates

A
  • trypsinogen
  • chymotrypsinogen
  • others
34
Q

Trypsin inhibitors

A

Prevents activation of trypsin

  • formed and stored in acinar cytoplasm
  • secreted by acinar cells (acini, ducts)
  • alpha-2 macroglobulin –> helps remove proteases from plasma, tags digestive enyzmes for removal
35
Q

Alpha-2 macroglobulin is synthesized in the

A

Liver

36
Q

Pancreatic lipase immunoreactivity

A

Increased = pancreatitis

  • enzymes are unchecked
  • activation in pancreas
  • released into the bloodstream
37
Q

Vasoactive intestinal polypeptide/peptide

A

Enteric neurotransmitter released by vagal neurons

  • stimulates ductal cells to secrete bicarb-rich fluid
  • inhibitory to rest of GIT = relaxation of sphincters and descending relaxation in the intestine
38
Q

Secretin

A

Hormone released by duodenal S cells

  • response to acidification
  • similar effect on ductal cells as VIP
  • stimulates bicarb from liver
39
Q

Acetylcholine

A

Released by postganglionic vagal neurons on or near acinar cells
- neurocrine stimulation

40
Q

CCK

A

Cholecystokinin

  • released by duodenal and jejunal cells into bloodstream to act as an endocrine hormone
  • secreted in response to AAs, FAs, and HCl
41
Q

Gastrin

A

In dogs:

  • released by antral G cells into bloodstream, where it circulates to acinar cell
  • endocrine stimulation
42
Q

______ and _____ stimulates pancreatic enzyme secretion in the guinea pig, but not dog/cat

A

Secretin and VIP

43
Q

Cephalic phase

A

Smelling, tasting, chewing

- minor (20%)

44
Q

Gastric phase

A

When food enters the stomach

- gastric distention

45
Q

Intestinal phase

A

Most important phase!!

- begins when food hits the small intestine

46
Q

The cephalic phase of pancreatic secretions has ________

A

Neuronal regulation

  • vagus stimulates parietal cell H secretion –> duodenal secretin release = pancreatic fluid and bicarb secretion
  • vagus stimulates gastrin from antral G cells –> pancreatic enzyme secretion (dogs) –> also stimulates parietal cells to secreted H = secretin secretion
47
Q

If a dog has pancreatitis, it may be painful for him to

A

Smell food

48
Q

In the gastric phase of pancreatic secretion, protein digestion products stimulate

A

Gastrin release

- HCl from parietal cell (secretin release) and pancreatic enzymes (dog)

49
Q

Gastric distension simulates the

A

Vagal reflex

- HCl release from parietal cells –> secretin secretion from S cells

50
Q

Distension from food hitting the stomach causes

A

Vagal stimulation –> release of Ach and enzymes –> VIP and bicarb secretion

51
Q

Intestinal phase of pancreatic secretion results in

A
  • fats, peptides –> CCK release from I cells = enzymes
  • decrease pH –> secretin release from S cells = bicarb secretion
  • large volume of fluid

Physiology (33 decks)

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