Exocrine Pancreas Flashcards
(51 cards)
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
2
Q
Exocrine functions of pancreas
A
- enzymes secreted into a duct
- ducts lead to external environment
- digestive enzymes
3
Q
Endocrine functions of pancreas
A
- hormones secreted into the blood
- function at distant sites, not on the cells that secreted them
- insulin
4
Q
Exocrine histologic anatomy
A
- acini: digestive enzymes
- ducts: bicarbonate
5
Q
Endocrine histologic anatomy
A
Islets of Langerhans
- alpha cells: glucagon
- beta cells: insulin
- delta cells: somatostatin/gastrin
- PP cell: pancreatic polypeptide
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
7
Q
Sympathetic innervation
A
Inhibitory!!!
- celiac plexus
- mesenteric plexus
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)
9
Q
In dogs, the bile duct enters _______
A
Major duodenal papilla
10
Q
Accessory pancreatic duct (dogs)
A
Most important
- enters minor duodenal papilla
- separate from bile duct
11
Q
Pancreatic duct (dogs)
A
Less important
- may not be present
- empties into major duodenal papilla separate from bile duct
12
Q
Most pancreatic secretions in the dog go into the _______
A
Accessory pancreatic duct
13
Q
Pancreatic duct (cats)
A
Most important
- enters major duodenal papilla –> after joining with the common bile duct first
14
Q
Accessory pancreatic duct (cats)
A
Only present in 20% of cats
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
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
17
Q
Intrinsic factor
A
Secreted by parietal cells in humans
- facilitates B12 absorption in the distal small intestine
18
Q
Lack of B12
A
Pernicious anemia in people
- diarrhea in dogs and cats
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
20
Q
Enzymes are only functional at a _______
A
Higher pH
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
Proteolytic enzymes following activation
- trypsin
- chymotrypsin: both split whole proteins or partially-digested peptides into smaller peptides
- carboxypeptidase: splits some peptides into individual amino acids
26
Pancreatic amylase
Hydrolyzes starches
- glycogen and others
- into di- or trisaccharides
27
Pancreatic lipase
Neutral fat --> FA + monoglycerides
- cholesterol esterase: hydrolysis of cholesterol esters
- phospholipase: separates FAs from phospholipids
28
Protection from auto-digestion
- 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
Zymogen
Prozymes (inactive enzyme)
- trypsinogen
- chymotrypsinogen
- activation required
30
Zymogens are synthesized by _______
Ribosomes
| - formation and storage in vesicles
31
Zymogen stimulation of the cell
Fusion of granules to plasma membrane --> release of content into glandular lumen --> secretion into duodenum
32
Zymogens are activated in the ______
Duodenum
| - enterokinase (brush border enzyme) --> activates trypsinogen into trypsin
33
Trypsin activates
- trypsinogen
- chymotrypsinogen
- others
34
Trypsin inhibitors
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
Alpha-2 macroglobulin is synthesized in the
Liver
36
Pancreatic lipase immunoreactivity
Increased = pancreatitis
- enzymes are unchecked
- activation in pancreas
- released into the bloodstream
37
Vasoactive intestinal polypeptide/peptide
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
Secretin
Hormone released by duodenal S cells
- response to acidification
- similar effect on ductal cells as VIP
- stimulates bicarb from liver
39
Acetylcholine
Released by postganglionic vagal neurons on or near acinar cells
- neurocrine stimulation
40
CCK
Cholecystokinin
- released by duodenal and jejunal cells into bloodstream to act as an endocrine hormone
- secreted in response to AAs, FAs, and HCl
41
Gastrin
In dogs:
- released by antral G cells into bloodstream, where it circulates to acinar cell
- endocrine stimulation
42
______ and _____ stimulates pancreatic enzyme secretion in the guinea pig, but not dog/cat
Secretin and VIP
43
Cephalic phase
Smelling, tasting, chewing
| - minor (20%)
44
Gastric phase
When food enters the stomach
| - gastric distention
45
Intestinal phase
Most important phase!!
| - begins when food hits the small intestine
46
The cephalic phase of pancreatic secretions has ________
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
If a dog has pancreatitis, it may be painful for him to
Smell food
48
In the gastric phase of pancreatic secretion, protein digestion products stimulate
Gastrin release
| - HCl from parietal cell (secretin release) and pancreatic enzymes (dog)
49
Gastric distension simulates the
Vagal reflex
| - HCl release from parietal cells --> secretin secretion from S cells
50
Distension from food hitting the stomach causes
Vagal stimulation --> release of Ach and enzymes --> VIP and bicarb secretion
51
Intestinal phase of pancreatic secretion results in
- fats, peptides --> CCK release from I cells = enzymes
- decrease pH --> secretin release from S cells = bicarb secretion
- large volume of fluid
