1.3.2 Epithelial Cell Structure and Function in the GI Tract Flashcards
What is going on in this image? Identify the letters.
Exocytosis of zymogen granules
C = centroacinar cell
L = lumen
A = acinar cells
What is a safer and more convenient substitute for glucose in ORT in underdeveloped countries?
Starch
Name 3 antimicrobial products (and their effects) released by paneth cells into the lumen of crypts.
defensins (also called cryptdins here)
lactoferrin (Fe-binding)
lysozyme (digests bacterial cell walls)
What portion of the pancreas is this? Identify the structures present
Exocrine pancreas
Acinus and acinar cells
How does the bacterial load change as you progress through the gut?
Bacterial load increases moving from the small intestine to large intestine
What is this an image of and what are the different parts?
Acinar cell of the pancreas
Increased levels of Golgi due to high synthesis
What some of the ways that gut bacteria can modify or alter their host?
What are some of the stimulators of acinar secretion?
VIP, Secretin (cAMP)
GRP, ACh (Ca++)
What is one of the most effective ways to treat a C. diff?
Fecal transplant (90% effective)
What are some of the intrinsic and extrinsic factors that affect gut bacteria?
Intrinsic: gastric acid, O2, motility, mucus, GI secretion, antimicrobial peptides, immunity
Extrinsic: diet, probiotics, PPIs, H2 blockers, antibiotics, prokinetics, laxatives, opioids, NSAIDs
In what two ways can a fiber-rich diet promote good colon health?
It helps regulate the amount of microbes as well as maintaining the mucus membrane
What are the stimulators of pancreatic secretions and what is their pathway?
VIP and Secretin - cAMP
GRP and Ach - Ca2+
What are the 5 effects of probiotics?
- Modulate intestinal immune function
- Promote epithelial homeostasis
- Neuromodulatory effects
- Block effects of pathogens
- Nutritional benefits
What is the mechanism of cholera toxin action on enterocytes and EC cells?
What is one of the major effects of enteric pathogens (ie cholera)?
Secretory diarrhea
Use of antibiotics can result in what type of GI infection?
C. diff
Describe the organization of crypts within the small intestine
How is electrolyte transport altered during enteric infection?
Decreased sodium reabsorption (NaCL)
Increased Cl- secretion
Identify these structures
What do each of the letters represent?
G = Golgi apparatus
C = condensing vacuole
S = mature secretory (zymogen) granules
M = mitochondrion
Identify the two stem cell populations found in the small intestine. Where are they found?
+4 stem cells: positioned ~4 cells from crypt base
Lgr5+: crypt base columnar stem cells which reside between Paneth cells, express the marker Lgr5
Describe the polarity of the exocrine acinar cell of the pancreas.
What is the mechanism through which enteric pathogens lead to secretory diarrhea?
What is this an image of?
Paneth cells
Through what mechanism can CCK indirectly activate the secretion from acinar pancreatic cells?
Through the parasympathetic nerve (Ach)
What organ is this? Identify the structures?
Pancreas
Arrows = Islets of Langerhans
Arrowhead = connective tissue septum
What is this an image of?
Exocytosis of zymogen granules
Identify the three cell types found in the small intestine
M = mast cell
Arrowhead = enteroendocrine cell
Arrow = Paneth cell
What is this an image of?
Fiber rich diet - left higher mucosa
Fiber free diet
What is the trick to oral rehydration therapy in treating people with enteric infections?
Sodium transport and glucose transport are coupled in the small intestine so that glucose accelerates absorption of solute and water.
What are the four functions of mucus in the GI tract
- Physical/chemical barrier (stomach/colon)
- Scaffold for defensive molecules including IgA
- Entrap microbes
- Lubricant
