GI 07

Question 1

Role of small intestinal phase

Answer 1

Digestion and absorption of nutrients in the Gi system; motility

Question 2

What 2 major factors contribute to inhibition or slowing of gastric emptying

Answer 2

Presence of fat in duodenum, presence of hydrogen ions in duodenum

Question 3

What hormone is secreted when fat is detected in the duodenum

Answer 3

CCK - this will slow gastric emptying via initiating pyloric contraction and gallbladder contraction, as well as RELAXING the sphincter of oddi and increasing pancreatic secretions

Question 4

The proteins put into the duodenum from the pancreas are a endocrine or exocrine function of the pancreas?

Answer 4

exocrine

Question 5

What kind of cells generate the pancreatic juice that is put into the duodenum

Answer 5

pancreatic acinar cells - these empty into the main pancreatic duct which meets the common bile duct to go into duodenum (sphincter of Oddi is what separates this duct from duodenum)

Question 6

Is exocrine or endocrine pancreatic secreting cells the majority of pancreatic volume

Answer 6

Exocrine

Question 7

2 components of pancreatic exocrine secretions

Answer 7

Aqueous component high in HCO3; enzymatic component

Question 8

What is the largest contributor to enzymatic digestion of a meal (gastric, salivary, or pancreatic secretions)?

Answer 8

Pancreatic secretions

Question 9

What is the largest contributor of bicarbonate in the GI tract

Answer 9

Pancreas - although biliary ductules and duodenal epithelial cells will also generate HCO3

Question 10

What part of the pancreatic secretion unit is stimulated by CCK

Answer 10

Acinus (acinar fluid)

Question 11

What part of the pancreatic secretory unit (exocrine) is stimulated by secretin

Answer 11

ductal fluid

Question 12

When luminal pH is low, what happens in small intestine?

Answer 12

S cells are triggered to release secretin

Question 13

What does secritin do?

Answer 13

stimulates secretion of bicarbonate - this also negatively feeds back and stops secretin release because the pH is being raised.

Question 14

What is wrong in cystic fibrosis as far as the ductal system goes

Answer 14

CFTR, a TM transporter of chloride, is fucked up- therefore bicarbonate transport is fucked up. Ductal cells are no longer able to secrete bicarbonate into lumen. Enzymes are still put out but pH is too low for them to be useful and enzymes precipitate out - pancreatic funciton is altered, glands atrophy

Question 15

What happens when fatty acids and amino acids interact with the small intestine

Answer 15

It triggers CCK release from I cells - this stimulates pancreatic acinar secretion endocrinely and stimulates neural reflexes that impinge on pancreas (vagovagal reflex that releases ch, GRP, and VIP nto enteric neurons) - leads to release of enzymes

Question 16

Pancreatic enzymes

Answer 16

Trypsinogen
chymotrypsinogen
proelastase
procarboxypeptidase A and B

Question 17

How are pancreatic zymogens activated

Answer 17

Enterokinase on brush border of small inestinal epithelial cells activates trypsin, and trypsin activates the other pancreatic zymogens (including itself)

Question 18

What is bile composed of (primarily)

Answer 18

Bile salts, phospholipids , proteins, cholesterol, bile pigments (ex. bilirubin), electrolytes (isotonic to plasma) - bile salts are detergents and form micelles

Question 19

why are bile salts important

Answer 19

lipids are hydrophobic so we need something to mix them up and bring them close to an aqueous environment

Question 20

After bile acids are secreted, what happens to it?

Answer 20

It travels along with food and are reabsorbe via enterohepatic cirulation in termial ileum

Question 21

What is the symporter for bile acids to be absorbed by in terminal ileum

Answer 21

Apical Na-Dependent bile acid transporter (ASBT)

Question 22

Is ASBT passive or active transporter

Answer 22

Active

Question 23

Is bile ever absorbed passively

Answer 23

Yes - bile acids that enter the colon can become deconjugated and reabsorbed passively

Question 24

What are the two contractile activities which exist in the small intestine

Answer 24

Segmentation and peristalsis

Question 25

Does segmentation result in net forward propulsion

Answer 25

no

Question 26

What is segmentation

Answer 26

Food is split between orad and caudad direction and then merged again - this leads to mixing, no forward movement

Question 27

Peristalsis

Answer 27

Food is squeezed forward - results in net forward movement

Question 28

Activating NTs of peristalsis

Answer 28

Ach and Substance P

Question 29

Inactivating NTs of peristalsis

Answer 29

VIP and NO

Question 30

Migrating motor complex

Answer 30

This is the periodic contraction of the small intestine, mediated by motilin, that occurs at 90m intervals during fasting to clear remaining gastric and intestinal contents out into duodenum (after a meal , motilin levels fall and these contractions are suspended)

Question 31

With regard to pancreatic secretions, what happens in the cephalic phase

Answer 31

they increase ( vagal and enteric nerves)

Question 32

with regard to pancreatic secretions, what happens in gastric phase

Answer 32

they increase (vagovagal / gastropancreatic reflexes)

Question 33

With regard to pancreatic secretions, what happens in intestinal phase

Answer 33

pH is low, leads to secretin being released –> increase in pancreatic secretion
peptides, FFA’s detected –> CCK released from I cells –> Pancreatic secretion
distention detected –> enteropancreatic / vagal reflex –> pancreatic secretion
CCK sensory enteric neurons –> pancreatic secretions