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PHSL 233 > L31 > Flashcards

L31 Flashcards

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1
Q

where is CCK secreted from and what are its functions

A

 released from I-cells in the duodenum due to fat and protein digestive products
 inhibits gastrin secretion in the antrum
 increases protein secretion in the pancreatic acini

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2
Q

where is Secretin released from and what is its function

A 
 released from S-cells in the
small intestine due to
acidification of the duodenum
 increases fluid secretion in the
pancreatic duct
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3
Q

what is the exo and endocrine parts of the pancreas

A

endocrine is the insulin and glucagon part (islet cells)

exocrine is the asein and the duct cells

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3
Q

what is the exo and endocrine parts of the pancreas

A

endocrine is the insulin and glucagon part (islet cells)

exocrine is the asein and the duct cells

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4
Q

describe the structure of the exocrine pancreas

A

there are 3 main parts, the lobules, ducts and secretory units

lobules
 acini

ducts
 intercalated
 common bile

secretory units
 acini
 intercalated ducts

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5
Q

describe the structure of the exocrine pancreas

A

there are 3 main parts, the lobules, ducts and secretory units

lobules
 acini

ducts
 intercalated
 common bile

secretory units
 acini
 intercalated ducts

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6
Q

the pancreas has 2 major ducts. where do these come together

A

the sphincter of oddi

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7
Q

the acini are the primary site for what??

A

fluid secretion

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8
Q

how many acinus per lobule

A

15-20 cells

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9
Q

what do acinus cells synthesise and secrete

A

 synthesis and secretion of
proteins
 secrete isotonic NaCl solution

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10
Q

what is the finction of intercalated ducts

A

 modify primary secretion by
secretion of HCO3-
rich fluid

Very different to salivary gland eg in the salivary gland the epithelium is tight but here it is leaky. Also here most of the fluid comes from the ducts

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10
Q

what is the finction of intercalated ducts

A

 modify primary secretion by
secretion of HCO3-
rich fluid

Very different to salivary gland eg in the salivary gland the epithelium is tight but here it is leaky. Also here most of the fluid comes from the ducts

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10
Q

what is the finction of intercalated ducts

A

 modify primary secretion by
secretion of HCO3-
rich fluid

Very different to salivary gland eg in the salivary gland the epithelium is tight but here it is leaky. Also here most of the fluid comes from the ducts

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11
Q

what is the differnt between the duct cells in the salivary gland compeared to in the pancras

A

Very different to salivary gland eg in the salivary gland the epithelium is tight but here it is leaky. Also here most of the fluid comes from the ducts

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11
Q

what is the differnt between the duct cells in the salivary gland compeared to in the pancras

A

Very different to salivary gland eg in the salivary gland the epithelium is tight but here it is leaky. Also here most of the fluid comes from the ducts

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12
Q

what is the differnt between the duct cells in the salivary gland compeared to in the pancras

A

Very different to salivary gland eg in the salivary gland the epithelium is tight but here it is leaky. Also here most of the fluid comes from the ducts

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12
Q

what is the differnt between the duct cells in the salivary gland compeared to in the pancras

A

Very different to salivary gland eg in the salivary gland the epithelium is tight but here it is leaky. Also here most of the fluid comes from the ducts

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13
Q

what volume of fluid does the pancreas secrete per day

A

1.5 L

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14
Q

what is the osmolarity of the pancreatic secretions

A

300mOsmol

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15
Q

what is the pH of the pancreatic secretions

A

7.8

slightly alkaline

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16
Q

what is the concentrations of ions in the pancreatic secretions

A 
Na = 140 
K = 10 
Cl = 70 
HCO3 = 80 
mmol/L
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17
Q

the stomach secretes bicarbonate into the blood (mostly) there is some into the lumen of the stomach

The pancreas and the liver also secrete bicarbonate into the lumen

This all comes together in a loop as in the stomach you make acid anhydrase and then in the intestine you nutrolise H+ by creating it back from bicarbonate

A

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18
Q

Volume and compositon of secretions

1-1.5 L of alkaline fluid and 5 -15 g protein secreted per day

where does the protein come from

A

 proteins - acinar cells

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19
Q

how many different proteins are secreted from the acinar cells

A

 20 different proteins secreted - mainly digestive enzymes

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20
what are zymogens what are some examples
 zymogens - inactive precursors of digestive enzymes  trypsinogen, chymotrypsinogen, procarboxypeptidase other digestive enzymes (not zymogens) amylase, lipase, colipase there is an enzymes for all major nutrient groups
21
where does the alkaline fluid come from in pancreatic secretion
 alkaline fluid - intercalated duct cells  essentially isosmotic NaHCO3 solution
22
what is the role of the alkaline fluid secreted from the pancreas
 neutralises acidic chyme from the stomach this is because the These enzymes needed for digestion dont work in acidic environment that is provided by the stomach therefore it needs to be neutralised
23
what stimulates pancreatic secretion
in absence of food  low basal secretion during the cephalic and gastric phase  limited secretion during intestinal phase - arrival of food in intestine  largest volume of secretion  cholecystokinin (CCK) and secretin also get minor regulation via vagus  acetylcholine
24
what is the stimulus for CCK
 fat, products of protein digestion in duodenal lumen
25
what is the stimulus for secretin
 acidic chyme in duodenal lumen
26
CCK and Secretin have different effects what are these
Secretin is important for increasing bicarbonate and decreasing CL whereas CCK has not effect CCK effects acini Secretin acts on the duct cells which is where 75% of the pancreatic secretion comes from
27
CCK and Secretin have different effects what are these
Secretin is important for increasing bicarbonate and decreasing CL whereas CCK has not effect CCK effects acini Secretin acts on the duct cells which is where 75% of the pancreatic secretion comes from
28
what % of pancreatic secretion comes from the duct cells
Secretin acts on the duct cells which is where 75% of the pancreatic secretion comes from
29
what stimulates acinar cells
CCK and vagus (ACh)
30
what do acinar cells secrete
 secrete small volumes of isotonic NaCl and digestive enzymes
31
what % of secretion are acinar cells responsible for
 primary fluid secretion (25% of total pancreatic solution)
32
what acts on duct cells
secretin
33
what do duct cells secrete
 secrete larger volumes of isosmotic NaHCO3 |  primary secretion modified by further secretion
34
Pancreatic secretion A. is hypotonic due to high Na+ re-absorption in pancreatic ducts. B. is stimulated by somatostatin. C. contains trypsinogen released from zymogen granules. D. is elevated during the gastric phase.
A. Iso because it is leaky therefore there is not Na reabsorption, you actually secrete it B. CCK and secretin D. there is limited secretion during the gastric phase it is largest during the intestinal phase C is correct
35
zymogen graduals in the acinar cells are responsible for the protein secretion
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36
CCK and ACh stimulate an increase in acinar cell secretion via....
increase in Ca
37
Acinar cells secrete isotonic NaCl solution by electrogenic Cl- secretion what channels are needed for this
Na/K ATPase K channel NKCC1 Cl channel in apical membrane Cl creates an electrical gradient, Na follows Cl (paracellular pathway) and water follows salt (paracellular pathway) because leaky epithelium
38
summery of acinar cells fluid secretion is driven by electrogenic Clsecretion ``` CCK and acetylcholine  stimulate increase in [Ca2+]i  activates a Ca2+ -dependent apical Cl- channel  increase in intracellular Ca2+ also stimulates the secretion of enzymes ``` results = the secretion of a small volume of isotonic NaCl solution containing a high concentration of digestive enzymes
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39
duct cells secrete large volumes of HCO3- rich solution what is the effect of this
 hydrates proteins secreted by acinar cells  alkalinises the solution bathing proteins  flushes protein out of ducts into small intestine  neutralises gastric acid Helps to flush into the small intestine but the main function is to neutralise the acid as the digestive enzymes wont work at the low pH
40
what is the secretion in duct cells stimulated by
stimulated by..  secretin (main stimulus) which acts through cAMP  also ACh
41
what is the driver of secretion in duct cells
 secretory epithelia secrete Cl ions not HCO3-  saw an exception to that with HCl secretion  in duct cells HCO3- drives secretion
42
Under resting conditions we don't have any release during the cephalic and gastric phase Under stimulated condition you have additional support of CFTR There is leaky epithelium and the electrical greident the Cl crates an electrical gradient. Bicarbonate adds to this therefore causes lots of water secretion
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43
what channels are in an activated duct cell
basolateral Na/K ATPase K channel Na/HCO3 cotransporter Na/H exchanger apical Cl/HCO3 exchanger when secretin binds (basolateral) it increases cAMP which causes CFTR to be inserted into the membrane which creates an electrical greident
44
what happens in the duct cell when CFTR gets inserted into the membrane
it causes secretion of HCO3 (via Cl/HCO3 exchanger) the Cl electrical gradient causes Na and water to move through the paracellular pathway
44
what happens in the duct cell when CFTR gets inserted into the membrane
it causes secretion of HCO3 (via Cl/HCO3 exchanger) the Cl electrical gradient causes Na and water to move through the paracellular pathway
45
what happens in cystic fibrosis at the level of the pancreas
Cystic fibrosis = mutation in CFTR therefore if the CFTR is not working then you cant secrete the bicarbonate rich fluid which means that they cant get the enzymes from the pancreas to the intestine therefore they are mellabsorbed because they cant further digest food for absorption Worst cases is they gat stuck in the pancreas and the pancreas starts digesting itself
46
Salivary vs pancreatic duct cell secretion
 tight (s) vs leaky epithelium (p)  chloride secreted to drive bicarbonate secretion (boosted by secretin in pancreas)  NO change in sodium content (pancreas). no ENaC because Na can move through the paracellular pathway  major site of fluid secretion in pancreas
47
summery of duct cell  dependent on apical Cl-/HCO3- exchanger  at rest this is inactive as very little Cl- in duct lumen  this is controlled indirectly via a cAMP-dependent Cl- channel (CFTR) activated by secretin  increase in cAMP = activation of apical Cl- channel (cAMP-activated)  Cl- diffuses into the lumen of the duct providing luminal Cl for apical Cl-/HCO3- exchanger  luminal Cl- exchanged for HCO3- which results in HCO3- secretion  Na+ diffuses across paracellular pathway due to potential set up by Cl- movement  water follows because of osmotic gradient  secretion of NaHCO3
,
48
The secretion of a bicarbonate-rich solution by pancreatic duct cells is driven by CCK, BECAUSE bicarbonate secretion in stimulated pancreatic duct cells is facilitated by CFTR.
the first statment is false and the second is true to be true the first statement should say srecretin not CCK
49
what is the liver responsible for
The liver is responsible for digesting fat
50
what is the function of the liver
1. processing of absorbed nutrients and control of metabolism 2. secretion and excretion (exocrine function)
51
how does the liver process absorbed nutrients and control of metabolism
gluconeogenesis, glucose buffering, fatty acid oxidation, synthesis of plasma proteins (e.g., albumin)
52
how does the liver have a role in secretion and excretion (exocrine function)
provision of bile acids and alkaline fluid to:  aid digestion and absorption of fats  neutralise gastric acid also causes...  degradation and conjugation of waste products of metabolism  detoxification of poisonous substances  excretion of waste metabolites and detoxified substance in bile
53
The liver either release's or stores glucose Albumin is the oncotic pressure in the kidney The liver is a duct secreting organ as well We are secreting metabolites as well as drugs and secretes a slightly alkaline fluid
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54
If you take an aspirin then it first goes to the liver. The liver is the gate keeper for our system. why is this is a problem for pharmaceutical reasons
if it does not pass through the liver then the drug will go straight back into the intestine and be excreted It can convert medications to nonfunctional metabolites (therefore they wont have an effect)
55
describe the anatomy of the liver
hepatic artery = blood supply portal vein and central vein. bile canaliculi and bile duct hepatocytes line canaliculi ducts secrete bicarbonate rich fluid
56
what is the volume of pancreatic secretions
0.5L per day
57
what is the composition of bile secreations
excretory products  bile pigments - waste products  cholesterol - excreted by liver  steroids, heavy metal, drugs products associated with digestion  HCO3- rich fluid - secreted by duct cells  bile salts (Emulsify the fat to get it digested)
58
why are bile salts amphipathic compounds
because they have a hydrophillic and hydrophobic surface therefore they are able to emulsify FFA, and cholesterol
59
what is the primary bile acid
cholic acid
60
there are 2 sources of bile salts. what are they
newly synthesized enterohepatic circulation (recycling)
61
what is the enterohepatic circulation
it is a mechanism in the small intestine that causes limited passive absorption of bile salts and active absorption in ileum the colon also plays a limited role it is about the reabsorption of bile salts
62
what % of bile salts are absorbed
95% the 5% that we lose is resynthesized
63
control of biliary secretion has 3 mechanisms. what are they
nervous, hormonal and bile salts
64
biliary secretion mainly happens in the intestinal phase. what causes this
hormonal  secretin stimulates production of HCO3- rich solution by ducts  CCK stimulates contraction of gallbladder bile salts  arrival of bile salts in portal venous blood stimulates absorption by liver and subsequent secretion
65
The liver produces a bicarbonate-rich bile, BECAUSE bile acids are required to reabsorb protein in the intestine.
the first statment is true and the second is false second statement should say fat to be correct
66
Functions of the liver  gluconeogenesis, glucose buffering, fatty acid oxidation, synthesis of plasma proteins (e.g., albumin), detoxification; Biliary secretion (stimulation: intestinal phase, CCK and secretin)  liver produces a bicarbonate-rich bile including bile acids, drugs and metabolites;  bile acids are used to reabsorb fat;  bile acids are recycled;
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PHSL 233 (31 decks)

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