Physiology of GI Tract III

Question 1

What factors stimulate pancreatic secretions?

Answer 1

Neurol and humoral mechanisms

NOTE: The acinar cells around the pancreatic gland produce a host of pancreatic enzymes. They are released into the pancreatic gland duct. This is driven by Ach, CCK, GRP, secretin and VIP.

Question 2

Pancreatic secretions are alkaline during the ________ phase of the meal.

Answer 2

Intestinal

NOTE: Initially the meal stimulated secretion of Na+ doesn’t change. The important thing is to get bicarb from the duct cells to neutralize the acid that enters the duodenum from the stomach. The amout of bicarnb increases as the pancreatic secretions increase to help control the acid levels.

Question 3

Proteins secreted by pancreatic acinar cells

Answer 3

Question 4

What affect does CCK have on the gall bladder and the sphincter of oddi?

Answer 4

CCK stimulates gallbladder contraction and sphinter of oddi relaxation by both neural and humoral pathways.

Question 5

What are the two basic functions of glucose insulinotropic peptide (GIP)?

Answer 5

• Release stored insulin from the pancreatic beta cells after eating a meal
  
  • Should happen within a few hours
• Slows down all upstream functions
  
  • Decreases motility

NOTE: GIP release is stimulated only by oral glucose and not intravenous glucose.

Question 6

What substances are secreted by the duodenum?

Answer 6

CCK, GIP, HCO3-, Secretin

Question 7

What substances are secreted by the ileum?

Answer 7

PYY and HCO3-

Question 8

Which substances are absorbed soley by the duodenum?

Answer 8

Fe

NOTE: Absorption of ions, nutrient, and H2O also happens here. Ions, nutrients, and H2O are absorpbed in all parts of the small intestine but decreases as you go down from the duodenum.

Question 9

Which substances are absorbed soley by the ileum?

Answer 9

Bile acids

B12

Question 10

Intraluminal digestion prepares the meal for surface digestion and absoption

Answer 10

NOTE: There is no brush border activity for fats and nodditional products

Question 12

Where does digestion of carbohydrates occur?

Answer 12

In the intestinal lumen and at the brush border

Question 13

Glucose and galatose enter the apical membrane through the ___________ transporter. Fructose enters the apical membtane through the ________ transporter. All three monosaccharides leave from the basolateral membrane throught the _________ transporter.

Answer 13

SGLT1; GLUT5; GLUT2

NOTE: The SGLT1 transporter requires active transport, so the Na/K+ ATPase creates a gradient to facilitate the uptake of glucose and galactose. Fructose taken up but GLUT5 via facilitated diffusion.

Question 14

What enzyme activates trypsinogen?

Answer 14

Enterokinase, which is an intestinal enzyme

Question 15

Function of bile acids

Answer 15

Bile acids take large fat molecles and emulsify them into smaller fat molecules

Question 16

Composition of a micelle

Answer 16

Question 17

Absorbed products of lipolysis are synthesized into triglycerides in the enterocytes and exit as ___________.

Answer 17

Chylomicrons

NOTE: The chylomicron is then emptied into the lymphatic system to eventually be moved into circulation

Question 18

Function of Peptide YY

Answer 18

• Inhibits:
  
  • Gastric acid secretion
  • Gastric emptying
  • Pancreatic secretion
  • Colonic motility
• Decreased transit rate

NOTE: PYY is released because of undigested carbs and fats; it has a net effect that slows down all upstream processes

Question 19

Where does water come from?

Answer 19

Question 20

Where does water absorption occuring?

Answer 20

Question 21

Where is most water reabsorption occuring?

Answer 21

Proximal part of the samll intestine

Question 22

What part of the GI tract is most efficient at water reabsorption?

Answer 22

Colon