Secretions Of Intestine Liver Gall Bladder Pancreas

Question 1

What occurs in the duodenum(2 things), jejunum(1 thing) and ileum(2 things)

Answer 1

Duodenum: acid neutralisation (pancreatic juice /bile)
Burners glands secretion of alkaline mucus in response to vagal, hormonal (secretin) and tactile stimuli

Jejunum: nutrient absorption

Ileum: b12 absorption, Peyers patches

Question 2

Villi: what does it contain, what is it surrounded by, what is secretion regulated by

What do crypts contain, and what do they do

Answer 2

Villi: contain blood vessel and lacteal supply. Villi is surrounded by brush border of absorptive enterocytes where enzymatic digestion takes place. Secretion regulated by ENS triggered by mucosal irritants/ tactile stimuli

Crypts: enterocytes secreting isotonic fluid, contains paneth cells and enter-endocrine cells

Question 3

CCK, motilin, neurotensin, secretin, serotonin, somastatin

Cells they are secreted from, where they originate and what do they do

Answer 3

CCK : I cells of villus, pancreas and gall bladder secretion
Motilin: m cells of crypts, gastric and intestinal motility
Neurotensin: n cells of villus, pancreatic secretion
Secretin: s cells of villus, pancreatic and biliary bicarbonate
Serotonin: enterochromaffin cells, motility, secretion, vasodilation
Somastatin: d cells of villus, inhibits gastrin

Question 4

When pancreatic and bile duct meet, what does duct become

Answer 4

Hepatopancreatic duct

Question 5

What are the 4 endocrine secretions of pancreas and what cells do they come from

Answer 5

Alpha cells secrete glucagon
Beta cells secrete insulin
Delta cells secrete somatostatin
F cells secrete polypeptidase

Question 6

In terms of exocrine glands of the pancreas, what are the four digestive enzymes secreted by the acinus and what is there release stimulated by

What do the ductal cells secrete

Answer 6

1) proteolytic enzymes secreted in inactive form
2) amylase hydrolyses starch, glycogen and other carbs to form di and tri saccharides
3) lipases, hydrolyses fat to form fatty acids and monoglycerides
4) trypsin inhibitor, prevents activation of trypsin to prevent pancreatic digestion

Bicarbonate and water

Question 7

Acinar cells secretes nacl , 5 step mechanism

Answer 7

1) na/k pump pumps na out of cell and k into cell
2) na/k/cl transporter transports na, k and cl into cell, activated by na gradient into cell
3) rise in k = k exits cell via basolateral channels
4) accumulation of cl= cl exits into acinus lumen via apical membrane cl channels
5) voltage of lumen now negative, so na follows

Question 8

3 step mechanism for duct secretion

Answer 8

1) ducts secrete hco3- via cl-/hco3- exchanger
2) CFTR channel recycles cl- back into cell
3) na+ secreted into duct lumen following hco3-, water follows via osmosis

Question 9

what is cystic fibrosis

what is treatment

Answer 9

lack of CFTR channel. ducts get blocked with pancreatic enzymes and mucus, and pancreas undergoes fibrosis. blocked ducts = impaired secretion of digestive enzymes= malabsorption
treatment: oral pancreatic enzyme supplements with meals

Question 10

what is pancreatitis
most common cause in women and in men
how is this pain classicly described

Answer 10

pancreatic enzymes are activated in pancreas leading to autodigestion of tissues
women gall stones, men alcohol
pain described as epigastric pain radiating to back, relieved by leaning forward

Question 11

how is autodigestion of pancreas prevented

Answer 11

enzymes from pancreas produced as zymogens, these are only activated when released into small intestine. trypsinogen is converted to trypsin by enterokinase bound to enterocyte brush border, trypsin cleaves/activates other zymogens

Question 12

cephalic phase of pancreatic secretion

Answer 12

less than 20%
sight, smell and taste of food > parasymp vagal activity > secretion of ACh and VIP by nerve endings > secretion of gastrin by g cells of antrum > enzyme rich secretion by acinar cells + secretion of bicarbonate rich fluids by duct cells> pancreatic juice

Question 13

gastric phase of pancreatic secretion

Answer 13

<10%
distension of stomach > vagovagal reflex > secretion of ACh, VIP by nerve endings and gastrin by g cells of antrum > enzyme rich secretion by acinar cells + secretion of bicarbonate rich fluids by duct cells> pancreatic juice

Question 14

intestinal phase of pancreatic secretion

Answer 14

> 70%
products of protein and fat digestion > secretion of CCK by I cells
AND
low pH duodenum> secretion of secretin by s cells

both lead to
enzyme rich secretion by acinar cells + secretion of bicarbonate rich fluids by duct cells> pancreatic juice

Question 15

step by step describe the fate of bile (4 steps) and what is function of bile

Answer 15

hepatocytes secrete bile into canaliculi > drain into bile ducts for modification, concentration and then direct secretion into duodenum> temporary storage in gall bladder> water and electrolytes reabsorbed, leaving bile salts, cholesterol, lecithin and bilirubin (waste product from Hb degradation)

function: >bile acids emulsifying fat for lipase action
>bile acids in fat digestion across intestinal mucosa

Question 16

where are bile acids reabsorbed

where are some bile acids lost to

Answer 16

most at distal ileum>portal vein> liver

conjugated bile acids reabsorbed at terminal ileum

deconjugated also reabsorbed, some lost to faeces

Question 17

control of bile release following food

1) fatty acid/acidic chyme
2) vagus nerve

Answer 17

CCK release> gallbladder contraction, relaxation of sphincter of Odi

weak contraction of gall bladder

Question 18

2 types of gall bladder disease

and what is first one commonly caused by

Answer 18

1) asymptomatic cholethiasis (gall stones)
2) biliary colic (blockage of cystic duct)

gall stones commonly caused by:
>too much water/ bile salt reabsorption from bile
>high fat diet = cholesterol precipitating
>inflamed epithelium (low grade chronic infection)