1.3.1 Gastric Secretion Flashcards
Identify. What is the white arrowhead marking?
White arrowhead = intracellular canaliculi
What do each of these endrocrine cells of the GI produce: enterochromaffin-like, G cells, D cells?
enterochromaffin-like: histamine
G cells: gastrin
D cells: somatostatin
What are two inhibitors of acid secretion from parietal cells?
PGE2 and Somatostatin
Why are chief cells basophilic staining?
abundant rough ER
What is this an image of?
What is marked by A? B?
A = Parietal cell
B = Chief cell
What is this an image of?
Tubulovesicle insertion in parietal cells
Describe the step-wise process that tubulovesicles (TV) form microvilli (MV).
Tubulovesicles (TV) are in the cytoplasm when the cell is at rest. They contain the proton pump (H+, K+-ATPase) which cannot elaborate acid secretion from this location in the cell.
Upon stimulus, TV are inserted into the apical plasma membrane (exocytosis). As they are inserted, a core of actin microfilaments (MF) is assembled and forms the core of these long microvilli.
When the stimulus ends, the microvilli are endocytosed and the TV reform, ending acid secretion.
Which part of the stomach is responsible for pulsatile secretion of chyme into the duodenum?
Antrum
What is the arrow pointing to?
A mucous cell
What are two other stimulators (and their receptors) of parietal cells? What cellular mechanism acts downstream?
Acetylcholine (M3) and Gastrin (CCK8)
PLC -> IP3 + DAG (Ca++)
What are some of the stimulators of secretion of pepsinogen from chief cells?
Secretin, VIP, PGE2, Beta adronergic agonists (cAMP)
Ach, Gastrin/CCK (PLC -> Ca++)
Identify the blue dots
M = mitochondria
MV = microvilli
What is one of the more important enzymes in M cells?
HRP enzyme
What are the two parts of the stomach?
Fundus and Antrum
What enzyme is responsible for stimulating the alkaline tide?
Carbonic Anhydrase II
Why are parietal cells eosinophilic staining?
The large amount of mitochondria
Identify
Arrowheads = parietal cells
Arrows = chief cells
What is the circled part?
Mucous cells:
- surface mucous cells (arrow)
- mucous neck cells
What are some proton pump inhibitors (PPI)?
Omeprazole, lansoprazole
What is the long term solution to epithelial damage in the stomach?
New cell growth
What are some of the short term responses to epithelial damage in the stomach?
Decreased acid prod
increased mucous secretion
increased PGE production
undamaged cells migrate to cover area of damage
What is the main stimulator of parietal cells? What cellular mechanism/pathway is utilized downstream?
Histamine
Adenylate Cyclase (ATP -> cAMP)
What are the signaling molecules in ECL cells on parietal cells?
Gastrin + Histamine is much stronger on parietal cells than gastrin alone
The importance of histamine is an example of potentiation. The Ca2+ signal stimulated by gastrin and acetylcholine produces a weak secretory effect. However, when combined with the cAMP signal stimulated by histamine, the parietal cell secretory response is much greater. The combined response exceeds the sum of the response to the two individual pathways = potentiation.
What is this an image of?
Gastric gland
What is the process of secreting IgA in the GI immune system?
What is this structure? Identify the arrow and arrowhead
Peyer’s Patch
Arrow = lymphoid aggregate
Arrowheads = lacteal (lymphatic capillaries)
What is rearranged to be more organized during the formation of microvilli when tubulovesicles are inserted into the cytoplasm of parietal cells?
Actin cytoskeleton
The insertion of tubulovesicles into the cytoplasm of parietal cells causes the formation of what?
Microvilli
What is the name for the specialized location for immune cells within the GI system? Where are they found?
Peyer’s patch; Ileum
What type of cell is this? What are marked with red dots?
Chief cells
Secretory vesicles
What is one of the possible side effects of proton pump inhibitors?
hypergastrinemia (uncertain significance)
What are the two main pumps used in acid secretion of parietal cells?
H,K ATPase
Potassium channel
At rest, what are present within parietal cells that integrate into the plasma membrane during acid secretion?
Tubulovesicles
(85% of the protein content is H,K ATPase pumps)
Draw the regulation of the parietal cells. Also know the pathways they use in the cell
What acts to indirectly inhibit parietal cell acid production?
CCK
What is a possible side effect of H2 histamine receptor antagonists?
Reduce production of intrinsic factor (leading to B12 deficiency)
What is circled in this image?
These are M cells - NOTE THEY ARE NOT ANTIGEN PRESENTING CELLS
What are two of the protective mechanisms in the stomach?
Production of mucous and bicarbonate
What are some of the H2 histamine receptor antagonists?
Cimetidine and rantidine
