1.3.2 Epithelial Cell Structure and Function in the GI Tract

Question 1

What is going on in this image? Identify the letters.

Answer 1

Exocytosis of zymogen granules

C = centroacinar cell

L = lumen

A = acinar cells

Question 2

What is a safer and more convenient substitute for glucose in ORT in underdeveloped countries?

Answer 2

Starch

Question 3

Name 3 antimicrobial products (and their effects) released by paneth cells into the lumen of crypts.

Answer 3

defensins (also called cryptdins here)

lactoferrin (Fe-binding)

lysozyme (digests bacterial cell walls)

Question 5

What portion of the pancreas is this? Identify the structures present

Answer 5

Exocrine pancreas

Acinus and acinar cells

Question 6

How does the bacterial load change as you progress through the gut?

Answer 6

Bacterial load increases moving from the small intestine to large intestine

Question 7

What is this an image of and what are the different parts?

Answer 7

Acinar cell of the pancreas

Increased levels of Golgi due to high synthesis

Question 8

What some of the ways that gut bacteria can modify or alter their host?

Answer 8

Question 9

What are some of the stimulators of acinar secretion?

Answer 9

VIP, Secretin (cAMP)

GRP, ACh (Ca++)

Question 10

What is one of the most effective ways to treat a C. diff?

Answer 10

Fecal transplant (90% effective)

Question 11

What are some of the intrinsic and extrinsic factors that affect gut bacteria?

Answer 11

Intrinsic: gastric acid, O2, motility, mucus, GI secretion, antimicrobial peptides, immunity

Extrinsic: diet, probiotics, PPIs, H2 blockers, antibiotics, prokinetics, laxatives, opioids, NSAIDs

Question 12

In what two ways can a fiber-rich diet promote good colon health?

Answer 12

It helps regulate the amount of microbes as well as maintaining the mucus membrane

Question 13

What are the stimulators of pancreatic secretions and what is their pathway?

Answer 13

VIP and Secretin - cAMP

GRP and Ach - Ca2+

Question 14

What are the 5 effects of probiotics?

Answer 14

1. Modulate intestinal immune function
2. Promote epithelial homeostasis
3. Neuromodulatory effects
4. Block effects of pathogens
5. Nutritional benefits

Question 15

What is the mechanism of cholera toxin action on enterocytes and EC cells?

Answer 15

Question 16

What is one of the major effects of enteric pathogens (ie cholera)?

Answer 16

Secretory diarrhea

Question 17

Use of antibiotics can result in what type of GI infection?

Answer 17

C. diff

Question 18

Describe the organization of crypts within the small intestine

Answer 18

Question 19

How is electrolyte transport altered during enteric infection?

Answer 19

Decreased sodium reabsorption (NaCL)

Increased Cl- secretion

Question 20

Identify these structures

Answer 20

Question 21

What do each of the letters represent?

Answer 21

G = Golgi apparatus

C = condensing vacuole

S = mature secretory (zymogen) granules

M = mitochondrion

Question 22

Identify the two stem cell populations found in the small intestine. Where are they found?

Answer 22

+4 stem cells: positioned ~4 cells from crypt base

Lgr5+: crypt base columnar stem cells which reside between Paneth cells, express the marker Lgr5

Question 23

Describe the polarity of the exocrine acinar cell of the pancreas.

Answer 23

Question 24

What is the mechanism through which enteric pathogens lead to secretory diarrhea?

Answer 24

Question 25

What is this an image of?

Answer 25

Paneth cells

Question 26

Through what mechanism can CCK indirectly activate the secretion from acinar pancreatic cells?

Answer 26

Through the parasympathetic nerve (Ach)

Question 27

What organ is this? Identify the structures?

Answer 27

Pancreas

Arrows = Islets of Langerhans

Arrowhead = connective tissue septum

Question 28

What is this an image of?

Answer 28

Exocytosis of zymogen granules

Question 29

Identify the three cell types found in the small intestine

Answer 29

M = mast cell

Arrowhead = enteroendocrine cell

Arrow = Paneth cell

Question 30

What is this an image of?

Answer 30

Fiber rich diet - left higher mucosa

Fiber free diet

Question 31

What is the trick to oral rehydration therapy in treating people with enteric infections?

Answer 31

Sodium transport and glucose transport are coupled in the small intestine so that glucose accelerates absorption of solute and water.

Question 32

What are the four functions of mucus in the GI tract

Answer 32

1. Physical/chemical barrier (stomach/colon)
2. Scaffold for defensive molecules including IgA
3. Entrap microbes
4. Lubricant