1
Q
biliary secretions
A
secretions from the liver, gallbladder, and associated ducts
2
Q
major physiological role of the pancreas
A
secrete pancreatic juice
3
Q
pancreatic juice
A
a mixture of pancreatic enzymes and an aqueous alkaline secretion
4
Q
pancreatic enzymes
A
- very important for digestion
- can almost completely digest food in absence of gastric secretions
5
Q
aqueous alkaline secretion
A
- will neutralize stomach acid
- pancreatic duct secretes a NaHCO3- rich fluid into the duodenal lumen
– largest component of pancreatic secretions (1-2L/day)
6
Q
what pH does the pancreatic enzyme function best at?
A
neutral or slightly alkaline
7
Q
what does the exocrine part of the pancreas have?
A
acini
- grape like clusters of secretory cells
8
Q
what do acini connect to?
A
ducts that empty into the duodenum
9
Q
trypsinogen
A
- converted to active trypsin
– by enterokinase which is embedded in luminal border of cells lining in duodenal mucosa - within secretory vesicles containing trypsinogen there is a trypsin inhibitor to protect pancreas in case it is accidentally activated
9
Q
3 major proteolytic enzymes
A
- major ones secreted are trypsinogen, chymotrypsinogen, and procarboxypeptidase
– all are secreted in inactive form
10
Q
chymotripsinogen
A
converted to chymotrypsin
- by trypsin
11
Q
procarboxypeptidase
A
converted to carboxypeptidase
- by trypsin
12
Q
pancreatic amylase
A
- similar to salivary amylase
– it converts polysaccharides into the disaccharide maltose
– it hydrolyzes starches, glycogen and most other carbs
– exception is cellulose!
13
Q
pancreatic lipase
A
- only enzyme in dig syst that can digest fats
- it hydrolyzes triglycerides into monoglycerides and free fatty acids
– both can be absorbed
14
Q
what control pancreatic secretions mainly
A
hormones
15
Q
what does the presence of chyme in the duodenum trigger the secretion of?
A
secretin and CCK
16
Q
secretin
A
- presence of acid causes duodenal and jujenal mucosa to release secretin into blood
- secretin then goes to pancreas
– stimulating the duct cells to increase their secretions of NaHCO3- rich fluid - amount of secretin released is proportional to amount of acid entering duodenum
17
Q
CCK
A
- primarily in response to presence of fats in duodenum and a less extent of protein
- when in the blood the CCK will go to pancreas to stim pancreatic acinar cells to increase dig enzyme secretion
- presence of carbs in duodenum doesn’t cause CCK secretion
- a high protein meal doesn’t preferentially release proteolytic enzymes
18
Q
with respect to digestion whats the most important role of the liver?
A
production of bile salts
19
Q
what are bile salts important for?
A
fat dig and absorption
20
Q
other functions of the liver
A
- metabolic processing of fats, carbs, and proteins after absorption
- detoxification and or degradation of body waste, hormones, drugs, and other foreign compounds
- synthesizing plasma proteins
- storage of glycogen, fats, iron, copper, and vitamins
- activation of vitamin D
- removal of RBCs and bacteria
- excreting cholesterol and bilirubin
21
Q
hepatic protal vein
A
brings into the liver to deliver anything that was absorbed
22
Q
hepatic artery
A
supplies arterial blood to deliver O2 and blood borne metabolites
23
Q
what’s teh functional unit of the liver?
A
lobules
24
what do bile ducts converge to form? and what does it do?
common bile duct
- which transports bile from liver -> duodenum
25
lobules
- hexagonal arrangements of tissues surrounding central vein
- at each of the 6 corners, theres a branch of the hepatic artery, branch of hepatic portal vein, and a bile duct
26
sinusoids
capillary like structures
- has blood from hepatic artery and portal vein that flowed from periphery
- they run between rows of liver cells towards central vein
27
what lines sinusoids?
Kupfer cells
- macrophages that remove old blood cells and bacteria
28
what does central vein in all liver lobules converge to form?
hepatic vein
- which carries blood away from liver
29
bile canaliculus
- between hepatic cells
- thin bile carrying channels
30
what are hepatocytes constantly doing?
secreting bile into canuliculus which then carries bile from center of lobule to periphery and into bile duct
31
what is each hepatocyte in contact w/
a sinusoid on one side and a bile canaliculus on the other
32
sphincter of odi
opening of bile duct into duodenum
- closed until bile is needed
- when it's closed the secreted bile is diverted back up common bile duct and into gallbladder for storage
33
composition of bile
- mainly bile salts
- cholesterol
- lecithin
- bilirubin
-- in an aq fluid similar to pancreatic NaHCO3 secretion
34
what are bile salts a derivative of?
cholesterol
35
where are also all bile salts reabsorbed?
back into ileum and transported back through hepatic portal system to liver
36
enterohepatic circulation
recycling of bile salts between small intestine and liver
1) secreted bile salts consist of 95% old recycled and 5% new
2) 95% of bile salts are reabsorbed by terminal ileum
3) reabsorbed bile salts are recycled by enterohepatic circulation
4) 5% of bile salts are lost in feces
37
Bile salt effects on fats
- detergent like
- convert large fat globules in chyme into lipid emulsion of small fat droplets (<1mm)
-- increases surface area of luminal fats for pancreatic lipase
- have a lipid soluble part
-- interacts w/ surface of fat droplets and neg charged water soluble end
-- allows decrease in surface tension of droplets and break them down into smaller droplets
38
colipase
- secreted by pancreas
- binds to lipase and bile salts to hold them at action site to breakdown triglycerides
39
micelles
the structure of lipid-soluble compounds surrounded by water soluble bile salts
- hydrophilic outside
- hydrophobic inside
- core has cholesterol
40
what does micellular formation allow?
lipid soluble substances to be transported within chyme to their site of absorption
41
Bilirubin
- not involved in digestion
- waste product secreted in bile
- comes from degradation of haemoglobin in old RBC
- yellow colour
- but when in dig tract, enzymes ( in L intestine) turn it brown (feces colour)
- some is absorbed in S intestine and then excreted in urine (gives urine it's yellow colour)
42
what colour would feces be w out bile secretions
greyish white
43
chemical regulation of bile secretions
- most potent chemical signal is bile salts
- although reabsorbed and returned to liver via enterohepatic circulation, they stim release of bile
44
hormonal regulation of bile secretions
- secretin stims the secretion of aq alkaline component of bile
- but doesn't stim secretion of bile salts
45
Neural regulation of bile secretion
- during cephalic phase, vagal stim of liver promotes bile release before food reaches stomach or intestine
46
how much does the gallbladder concentrate bile secretions?
5-10 times
47
what does the release of CCK do to the gallbladder?
causes it to contract and causes the sphincter of Oddi to relax allowing bile to flow into duodenum
48
gallstones
- bile salts the precipitated due to high conc. in gallbladder
49
if gallbladder is removed, where does bile get stored?
common bile duct, which dilates
PHGY216-FINAL
flashcards
Decks in class (16)
# Cards
-
Module 4: Section 136
-
Module 4: Section 228
-
Module 4: Section 330
-
Module 4: Section 454
-
Module 4: Section 516
-
Module 4: Section 637
-
Module 5: Section 115
-
Module 5: Section 223
-
Module 5: Section 321
-
Module 5: Section 427
-
Module 6: Section 146
-
Module 6: Section 229
-
Module 6: Section 351
-
Module 6: Section 450
-
Module 6: Section 534
-
Module 6: Section 629
