1.3.1 Gastric Secretion

Question 1

Identify. What is the white arrowhead marking?

Answer 1

White arrowhead = intracellular canaliculi

Question 2

What do each of these endrocrine cells of the GI produce: enterochromaffin-like, G cells, D cells?

Answer 2

enterochromaffin-like: histamine

G cells: gastrin

D cells: somatostatin

Question 3

What are two inhibitors of acid secretion from parietal cells?

Answer 3

PGE2 and Somatostatin

Question 4

Why are chief cells basophilic staining?

Answer 4

abundant rough ER

Question 5

What is this an image of?

Answer 5

Question 6

What is marked by A? B?

Answer 6

A = Parietal cell

B = Chief cell

Question 7

What is this an image of?

Answer 7

Tubulovesicle insertion in parietal cells

Question 8

Describe the step-wise process that tubulovesicles (TV) form microvilli (MV).

Answer 8

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.

Question 9

Which part of the stomach is responsible for pulsatile secretion of chyme into the duodenum?

Answer 9

Antrum

Question 10

What is the arrow pointing to?

Answer 10

A mucous cell

Question 11

What are two other stimulators (and their receptors) of parietal cells? What cellular mechanism acts downstream?

Answer 11

Acetylcholine (M3) and Gastrin (CCK8)

PLC -> IP3 + DAG (Ca++)

Question 12

What are some of the stimulators of secretion of pepsinogen from chief cells?

Answer 12

Secretin, VIP, PGE2, Beta adronergic agonists (cAMP)

Ach, Gastrin/CCK (PLC -> Ca++)

Question 13

Identify the blue dots

Answer 13

M = mitochondria

MV = microvilli

Question 14

What is one of the more important enzymes in M cells?

Answer 14

HRP enzyme

Question 15

What are the two parts of the stomach?

Answer 15

Fundus and Antrum

Question 16

What enzyme is responsible for stimulating the alkaline tide?

Answer 16

Carbonic Anhydrase II

Question 17

Why are parietal cells eosinophilic staining?

Answer 17

The large amount of mitochondria

Question 18

Identify

Answer 18

Arrowheads = parietal cells

Arrows = chief cells

Question 19

What is the circled part?

Answer 19

Mucous cells:

• surface mucous cells (arrow)
• mucous neck cells

Question 20

What are some proton pump inhibitors (PPI)?

Answer 20

Omeprazole, lansoprazole

Question 21

What is the long term solution to epithelial damage in the stomach?

Answer 21

New cell growth

Question 22

What are some of the short term responses to epithelial damage in the stomach?

Answer 22

Decreased acid prod

increased mucous secretion

increased PGE production

undamaged cells migrate to cover area of damage

Question 23

What is the main stimulator of parietal cells? What cellular mechanism/pathway is utilized downstream?

Answer 23

Histamine

Adenylate Cyclase (ATP -> cAMP)

Question 24

What are the signaling molecules in ECL cells on parietal cells?

Answer 24

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.

Question 25

What is this an image of?

Answer 25

Gastric gland

Question 26

What is the process of secreting IgA in the GI immune system?

Answer 26

Question 27

What is this structure? Identify the arrow and arrowhead

Answer 27

Peyer’s Patch

Arrow = lymphoid aggregate

Arrowheads = lacteal (lymphatic capillaries)

Question 28

What is rearranged to be more organized during the formation of microvilli when tubulovesicles are inserted into the cytoplasm of parietal cells?

Answer 28

Actin cytoskeleton

Question 29

The insertion of tubulovesicles into the cytoplasm of parietal cells causes the formation of what?

Answer 29

Microvilli

Question 30

What is the name for the specialized location for immune cells within the GI system? Where are they found?

Answer 30

Peyer’s patch; Ileum

Question 31

What type of cell is this? What are marked with red dots?

Answer 31

Chief cells

Secretory vesicles

Question 32

What is one of the possible side effects of proton pump inhibitors?

Answer 32

hypergastrinemia (uncertain significance)

Question 33

What are the two main pumps used in acid secretion of parietal cells?

Answer 33

H,K ATPase

Potassium channel

Question 34

At rest, what are present within parietal cells that integrate into the plasma membrane during acid secretion?

Answer 34

Tubulovesicles

(85% of the protein content is H,K ATPase pumps)

Question 35

Draw the regulation of the parietal cells. Also know the pathways they use in the cell

Answer 35

Question 36

What acts to indirectly inhibit parietal cell acid production?

Answer 36

CCK

Question 37

What is a possible side effect of H2 histamine receptor antagonists?

Answer 37

Reduce production of intrinsic factor (leading to B12 deficiency)

Question 38

What is circled in this image?

Answer 38

These are M cells - NOTE THEY ARE NOT ANTIGEN PRESENTING CELLS

Question 39

What are two of the protective mechanisms in the stomach?

Answer 39

Production of mucous and bicarbonate

Question 40

What are some of the H2 histamine receptor antagonists?

Answer 40

Cimetidine and rantidine