Stomach

Question 1

three regions of the stomach

Answer 1

cardia, body/corpus, antrum

Question 2

covers the entire surface of the stomach

Answer 2

viscid mucous

Question 3

characteristic of the cardia, body, and antrum of stomach

Answer 3

cardia - no acid secreting cells but responsible for mucous and HCO3-

body - gastric gland, parietal and chief cells, mucous secreting neck cells, ECL cells which release histamine

antrum - pyloric glands contain endocrine cells (gastrin G cell and somatostatin D cells) and chief cells (secrete pepsinogen)

Question 4

what is the motor and protection function of the stomach

Answer 4

motor - reservoir, mixing, kneading, regulated emptying

protection - destroys pathogens

Question 5

what is the exocrine and endocrine secretion function of the stomach

Answer 5

exocrine - H+, intrinsic factor, pepsinogen, mucus, HCO3, H2O, gastric lipase

endocrine - gastrin and somatostatin

Question 6

some other motor functions of the stomach

Answer 6

• Relaxation and dilation to receive and store food
• Contracts to mix food with water and gastric secretions
• Churning: grind food to decrease particle size
• Moves the resultant chyme through the pyloric sphincter into the duodenum- at an appropriate rate

Question 7

stomach motility in fasting state

Answer 7

in fasting state: stimulation of the migration motor complex which cleans the gut every 1-2 hours (or 90 mins)

Question 8

stomach motility in fed state

Answer 8

• when meal enter stomach: vago-vagal reflex (receptive relaxation & accomodation)
• peristalsis begins: increased gastric pressure, slow sustained propulsive contraction that pushes food towards the closed pyloric sphincter in the antrum (retropulsion - no food leaves the stomach in the immediate post prandial phase)
• antral systole: contractions of distal stomach grinds food and mixes it with gastric juices –> powerful contractions “antral systole” force food back for more mixing

Question 9

amount of chyme that goes through the pyloric sphincter and the size of particles

Answer 9

1mL

particles less than 2mm

Question 10

what is pyloric stenosis

Answer 10

hypertrophy of pyloric sphincter which causes project vomiting from force exerted on pylorus

Question 11

characteristics seen in patients with pyloric stenosis

Answer 11

• occurs mainly in children and it makes them always hungry
• dehydrated
• olive shaped mass felt in right upper quadrant
• string sign (where pylorus is constricted) on CT scan
• mushroom sign (aka kirklin sign) on CT

Question 12

emptying of stomach is regulated by what

Answer 12

ANS and gut hormones

Question 13

types of contractions in motility

Answer 13

tonic contraction - low amplitude and in orad region

phasic contraction - caudad region

Question 14

rates of emptying of different fluids and materials in descending order

Answer 14

water or isotonic saline > acid and caloric fluids > fatty material

Question 15

what initiates the peristaltic wave that leads to circumferential constrictor waves&raquo_space; mixing, grinding, and propeling

Answer 15

pacemaker

Question 16

what is dumping syndrome

Answer 16

rapid gastric emptying that leads to distension of proximal small intestine

Question 17

what causes diarrhea in dumping syndrome

Answer 17

hypertonic fluid pulling fluid into the lumen

Question 18

symptoms of dumping syndrome

Answer 18

tachycardia, diarrhea, sweating, hypertension, flushing, palpitation, abdominal discomfort, autonomic reflexes –> release of GIT hormones

Question 19

cell type in pit or neck of the oxyntic gland and what do they secrete

Answer 19

mucus surface cells and mucus neck cells

they secrete mucus, bicarbonate, and water

Question 20

what does HCl and intrinsic factor do

Answer 20

HCl - activates pepsin, kills bacteria, denatures protein

intrinsic factor - activates vit b12 to enable absorption in lumen

Question 21

what increases secretion of parietal cells

Answer 21

gastrin, acetylcholine, histamine

Question 22

function of pepsinogen and gastric lipase

Answer 22

pepsinogen - digest proteins once cleaved to pepsin

gastric lipase - starts fat digestion

Question 23

what stimulates secretion of chief cells

Answer 23

acetylcholine and secretin

Question 24

what increases secretion in the neck/pit of the oxyntic gland

Answer 24

acetylcholine

Question 25

cell types after the neck of the oxyntic gland and what they secrete

Answer 25

parietal cells (oxyntic) –> secrete HCl, intrinsic factor, water

Question 26

cells active in base of oxyntic gland and what they secrete

Answer 26

peptic chief cells –> secrete pepsinogen, gastric lipase, water

Question 27

area of stomach that is oxyntic gland and that is pyloric area

Answer 27

oxyntic gland - 80%

pyloric - 20%

Question 28

explain the mechanism for the secretion of gastric acid/HCl

Answer 28

• H+ is pumped out of the cell via the H+/K+ ATPase on the apical surface
• the K+ leaks back out into the lumen via a channel to provide the K+ needed for the exchange for H+
• the H+ is provided by CO2 coming into cell and with H20 and CA forming H2CO3 which dissociates to H+ and HCO3-
• the HCO3- is pumped back into the plasma (alkaline tide) in exchange for Cl- (using HCO3-/Cl- exchanger)
• the Cl then exits the cell into the lumen to provide the Cl- to use to make HCl with the already secreted H+

Question 29

what protects the mucosa

Answer 29

mucous gel barrier

Question 30

oxyntic fluid vs. non oxyntic fluid

Answer 30

oxyntic fluid - high H+, Cl-, and K+ with low Na and no HCO3

non oxyntic fluid - high HCO3, Na, Cl with low K+ and H+

Question 31

what is happening when you vomit

Answer 31

you are getting rid of acid (HCl) so you have an increase in bicarb making person alkalotic –> metabolic alkalosis

also because of decrease in H+, K+ will replace H+ on the transporter to be secreted hence person become hypokalemic

Question 32

time spent in cephalic and gastric phase in stimulation of acid secretion

Answer 32

cephalic - 30%

gastric - 50%

Question 33

what is happening in the cephalic phase

Answer 33

vagus nerve is stimulated due to sight or smell of food –> stimulation of acetylcholine which triggers –> parietal cells, gastrin releasing peptide (act on G cells to produce gastrin which acts on parietal cells to produce HCl)

Question 34

negative feedback for HCl - how do you stop its production

Answer 34

increased H+ –> inhibits G cells
increased H+ –> increases D cells (somatostatin) which inhibits G cells
if G cells are inhibited then they can’t act on parietal cells to release HCl

Question 35

more ways to inhibit parietal cells

Answer 35

somatostatin can directly inhibit it
somatostatin can inhibit ECl which releases histamine
PGE2 can directly inhibit it

Question 36

what happens if fats, acids, proteins, or hyperosmolar fluid gets into the small intestine

Answer 36

stimulation of enteric hormones like CCK, secretin, GIP, neurotensin, peptide YY, VIP, somatostatin

Question 37

what digestive enzymes are present in the stomach and what they digest

Answer 37

gastric amylase - starch
gastric lipase - butter fat
intrinsic factor - facilitate b12 absorption
pepsin - protein

Question 38

what does chief cell secrete

Answer 38

pepsinogen which in presence of pH less than 5 is activated to pepsin

Question 39

importance of bicarb rich zone in protection of the mucosa

Answer 39

• if any of the H+ is able to cross the mucus gel barrier into the bicarb rich zone, the bicarb can neutralize the ion
• also inactivates pepsinogen so that there is no protein degradation of the epithelium

Question 40

what does the integrity of the defense barrier depend on

Answer 40

balance of defensive and aggressive factors so you want to have more bicarb, mucus, blood flow, growth factors, cell renewal, prostaglandins

Question 41

treatment for pyloric

Answer 41

antibiotics