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PHSL 233 > L31 > Flashcards

L31 Flashcards

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

j

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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
Q

what are zymogens

what are some examples

A

 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

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21
Q

where does the alkaline fluid come from in pancreatic secretion

A

 alkaline fluid - intercalated duct cells

 essentially isosmotic NaHCO3
solution

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22
Q

what is the role of the alkaline fluid secreted from the pancreas

A

 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

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23
Q

what stimulates pancreatic secretion

A

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

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24
Q

what is the stimulus for CCK

A

 fat, products of protein digestion in duodenal lumen

25
Q

what is the stimulus for secretin

A

 acidic chyme in duodenal lumen

26
Q

CCK and Secretin have different effects

what are these

A

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
Q

CCK and Secretin have different effects

what are these

A

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
Q

what % of pancreatic secretion comes from the duct cells

A

Secretin acts on the duct cells which is where 75% of the pancreatic secretion comes from

29
Q

what stimulates acinar cells

A

CCK and vagus (ACh)

30
Q

what do acinar cells secrete

A

 secrete small volumes of isotonic NaCl and digestive enzymes

31
Q

what % of secretion are acinar cells responsible for

A

 primary fluid secretion (25% of total pancreatic solution)

32
Q

what acts on duct cells

A

secretin

33
Q

what do duct cells secrete

A

 secrete larger volumes of isosmotic NaHCO3

 primary secretion modified by further secretion

34
Q

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

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
Q

zymogen graduals in the acinar cells are responsible for the protein secretion

A

j

36
Q

CCK and ACh stimulate an increase in acinar cell secretion via….

A

increase in Ca

37
Q

Acinar cells secrete isotonic NaCl solution by electrogenic Cl- secretion

what channels are needed for this

A

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
Q

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

A

j

39
Q

duct cells secrete large volumes of HCO3- rich solution

what is the effect of this

A

 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
Q

what is the secretion in duct cells stimulated by

A

stimulated by..
 secretin (main stimulus) which acts through cAMP

 also ACh

41
Q

what is the driver of secretion in duct cells

A

 secretory epithelia
secrete Cl ions not HCO3-
 saw an exception to that with HCl secretion

 in duct cells HCO3- drives
secretion

42
Q

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

A

l

43
Q

what channels are in an activated duct cell

A

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
Q

what happens in the duct cell when CFTR gets inserted into the membrane

A

it causes secretion of HCO3 (via Cl/HCO3 exchanger)

the Cl electrical gradient causes Na and water to move through the paracellular pathway

44
Q

what happens in the duct cell when CFTR gets inserted into the membrane

A

it causes secretion of HCO3 (via Cl/HCO3 exchanger)

the Cl electrical gradient causes Na and water to move through the paracellular pathway

45
Q

what happens in cystic fibrosis at the level of the pancreas

A

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
Q

Salivary vs pancreatic duct cell secretion

A

 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
Q

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

A

,

48
Q

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.

A

the first statment is false and the second is true

to be true the first statement should say srecretin not CCK

49
Q

what is the liver responsible for

A

The liver is responsible for digesting fat

50
Q

what is the function of the liver

A
  1. processing of absorbed nutrients and control of metabolism
  2. secretion and excretion (exocrine function)
51
Q

how does the liver process absorbed nutrients and control of metabolism

A

gluconeogenesis, glucose buffering, fatty acid oxidation, synthesis of plasma proteins (e.g., albumin)

52
Q

how does the liver have a role in secretion and excretion (exocrine function)

A

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
Q

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

A

k

54
Q

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

A

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
Q

describe the anatomy of the liver

A

hepatic artery = blood supply

portal vein and central vein.

bile canaliculi and bile duct

hepatocytes line canaliculi

ducts secrete bicarbonate rich fluid

56
Q

what is the volume of pancreatic secretions

A

0.5L per day

57
Q

what is the composition of bile secreations

A

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
Q

why are bile salts amphipathic compounds

A

because they have a hydrophillic and hydrophobic
surface

therefore they are able to emulsify FFA, and cholesterol

59
Q

what is the primary bile acid

A

cholic acid

60
Q

there are 2 sources of bile salts. what are they

A

newly synthesized

enterohepatic circulation (recycling)

61
Q

what is the enterohepatic circulation

A

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
Q

what % of bile salts are absorbed

A

95%

the 5% that we lose is resynthesized

63
Q

control of biliary secretion has 3 mechanisms. what are they

A

nervous, hormonal and bile salts

64
Q

biliary secretion mainly happens in the intestinal phase. what causes this

A

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
Q

The liver produces a bicarbonate-rich bile,

BECAUSE

bile acids are required to reabsorb protein in the
intestine.

A

the first statment is true and the second is false

second statement should say fat to be correct

66
Q

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;

A

j

PHSL 233 (31 decks)

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