Lower GIT (berne Ch. 29-30)

Question 1

This can result when enzymes release by this organ are proteolytically activated before they have reached their appropriate site of action in the small intestinal lumen

Answer 1

Pancreatitis

• • Pancreatic juice contains a variety of trypsin inhibitors to reduce the risk of such premature activation because trypsin is the activator of other pro-forms of enzymes secreted in pancreatic juice
• *Second level of protection lies in the fact that trypsin can itself be degraded by other trypsin molecules

Question 2

Considered the effector arm of a pH regulatory system designed to respond to luminal acid in the small intestine and secrete just enough bicarbonate to restore pH to neutrality

Answer 2

The ducts of the pancreas

Question 3

In the pancreatic duct cells, bicarbonate secretion is dependent on what transporter?

Answer 3

Cystic fibrosis transmembrane conductance regulator (CFTR)
**secretin increases cAMP in the ductular cells and thereby opens CFTR Cl- channels and causes an outflow of Cl- in the duct lumen This secondarily drives the activity of an adjacent antiporter that exchanges the chloride ions for bicarbonate

Question 4

The bicarbonate needed for secretory process in the pancreatic duct cells is derived from two sources. Some is taken up across the basolateral membrane of the ductular epithelial cells via what symporter?

Answer 4

NBC-1 (sodium-bicarbonate cotransporter type 1) – 2 bicarbonate: 1 Na

Question 5

Pancreatic ductules is to secretin; pancreatic acinar cells is to _____

Answer 5

CCK (cholecystokinin)

Question 6

A genetic disease that affects the function of a variety of epithelial organs, including the lung, intestine, biliary system, and pancreas

Answer 6

Cystic fibrosis
** The disease is caused by a mutation in the CFTR which impairs the ability to hydrate and thus alkalinize the luminal contents

Question 7

What are the two luminally acting releasing factors that regulate the release of CCK?

Answer 7

CCK-releasing factor (or peptide) and monitor peptide

Question 8

In protein digestion, particularly in the small intestine, inactive proteases released by the pancreas are activated by what enzyme located only in the brush border of small intestinal epithelial cells?

Answer 8

Enterokinase

Question 9

Endopeptidase that is capable of cleaving basic amino acids only at internal bonds within the peptide chain

Answer 9

Trypsin

Question 10

Endopeptidase that is capable of cleaving neutral amino acids only at internal bonds within the peptide chain

Answer 10

Chymotrypsin and elastase

Question 11

Ectopeptidases that cleave single amino acids from the end of the peptide chain

Answer 11

Carboxypeptidase A – neutral AA

Carboxypeptidase B – basic AA

Question 12

The peristaltic motor patterns that occur during fasting are organized into sequence of phases known as ______

Answer 12

Migrating motor complex

Question 13

Characterized as an “ileal brake” in that it is released if nutrients, especially fat, are not absorbed by the time that the meal reaches the terminal ileum and proximal part of the colon

Answer 13

Peptide YY

Question 14

True or false

Propulsive motility in the colon is less effective than in the small intestine

Answer 14

True

Question 15

True or false

The rectum lack circular muscles and is surrounded only by longitudinal muscle fibers

Answer 15

True

Question 16

Voluntary input from the spinal cord via what branches of what nerve regulates the contraction of the external anal sphincter and muscles of the pelvic floor

Answer 16

Pudendal nerve

Question 17

Short duration contraction in the colon is to ______: long duration contraction in the colon is to _______

Answer 17

Circular muscle; longitudinal muscle

Question 18

Fluid absorption in the colon is driven by three transport processes

Answer 18

Electroneural NaCl absorption

Absorption of short-chain fatty acids (acetate, propionate and butyrate) – together with Na through sodium-monocarboxylate transporter

Absorption of Na – through epithelial channel ENaC localized to the distal part of the colon