16 Esophagus and Stomach

Question 1

Is the buccal phase of swallowing voluntary or involuntary?

Answer 1

Voluntary– begins with opening mouth, chewing, tongue movement to push food up and back

Question 2

Is the pharyngeal phase of swallowing voluntary or involuntary?

Answer 2

involuntary

Question 3

Is the epiglottis pulled down when swallowing?

Answer 3

No–the larynx is pulled upward and the food pushes the epiglottis down to full close the hole

Question 4

What relaxes is the pharyngeal phase of swallowing?

Answer 4

upper esophageal sphincter relaxes

Question 5

What nerves are mediating the pharyngeal phase of swallowing?

Answer 5

V, IX, X, and XII

Question 6

T-F respiration continues in the act of swallowing?

Answer 6

false

Question 7

What type of peristalsis is initiated by swallowing?

Answer 7

primary peristalsis

Question 8

What type of peristalsis occurs in response to stretching of the esophagus?

Answer 8

secondary peristalsis [usually by retained food or refluxed gastric fluid not accompanied by a swallow]

Question 9

As the upper esophageal sphincter closes what happens to the lower esophageal sphincter?

Answer 9

it opens and peristalsis begins

Question 10

When does the LES finally close?

Answer 10

after the contraction wave reaches the stomach—this prevents a reflux of gastric contents into the esophagus

Question 11

Control of the esophageal peristalsis occurs via what nerve?

Answer 11

vagus nerve and intrinsic plexuses in the wall of the esophagus

Question 12

What are the 3 major stomach divisions?

Answer 12

cardia, body, antrum

Question 13

The body of the stomach contains which of the gastric gland cell types?

Answer 13

parietal
mucus
chief
enterochromaffin-like

Question 14

In the antrum, what gastric gland cell types are there?

Answer 14

mucus
chief
enterochromaffin-like
G cells
[NO PARIETAL CELLS]

Question 15

The foveolar epithelial cells in the stomach largely secrete what?

Answer 15

bicarb and mucus [contain multiple mucin-containing granules in the apical region]

Question 16

What are the 4 major functions of the stomach?

Answer 16

food accommodation
mechanical breakdown
secretion
digestion

Question 17

Where does the majority of accommodation occur?

Answer 17

in the fundus

Question 18

The resulting food mixture of mechanical breakdown in the stomach is called?

Answer 18

chyme

Question 19

What are the major things secreted by the stomach?

Answer 19

acid, fluid, electrolytes, bicarb

Question 20

How much fluid do the gastrin glands produce in a given day?

Answer 20

around 2 liters

Question 21

What is the primary cation in the stomach when acid secretion is not induced?

Answer 21

Na

Question 22

What is the primary cation in the stomach when acid secretion is increased?

Answer 22

H [Na become remarkably low]

Question 23

When do gastric pepsin function best?

Answer 23

low pH

Question 24

What are the 3 major functions for acid production in the stomach?

Answer 24

• optimum pepsin function
• bactericide
• physical breakdown of food

Question 25

T-F---stomach acid is essential for digestion?

Answer 25

false

Question 26

During resting state, where are the H-K ATPase molecules found in the parietal cell?

Answer 26

contained within intracellular tubulovesicles

Question 27

What part of the parietal cell do the proton pumps fuse with upon activation of parietal cells?

Answer 27

canalicular membrane

Question 28

What other channels are inserted into canalicular membrane upon parietal cell activation?

Answer 28

K and Cl

Question 29

H-K ATPase is a heterodimer of what units?

Answer 29

alpha [catalytic] and beta [delivery to apical membrane]

Question 30

What drug covalently binds to the proton pump on the lumenal side and inhibits it?

Answer 30

PPI

Question 31

T-F--water passively follows HCL into lumen

Answer 31

True

Question 32

Protons in stomach acid are produced by what?

Answer 32

carbonic anhydrase

Question 33

How is HCO3 created in the parietal cell secreted?

Answer 33

Cl- HCO3- exchanger on basolateral side

Question 34

What are the 3 secretagogues?

Answer 34

gastrin, Ach, and histamine

Question 35

What is the strongest direct stimulator of parietal cells? what does it act on? what is it produced by?

Answer 35

Histamine--H2 receptor of parietal cells---produced by ECL cells

Question 36

Is the principal action of gastrin and Ach direct or indirect?

Answer 36

indirect via stimulation of histamine release from ECL cells

Question 37

Do H2 blockers strongly block acid production even with gastrin or ACh stimulation?

Answer 37

yes [this is the evidence that ACh and gastrin act in an indirect manner]

Question 38

What is gastrin produced by? where are they located? what are the 2 major forms?

Answer 38

G cells, in the antrum and duodenum, little and big gastrin

Question 39

What are the 3 major effects of gastrin on the GI tract?

Answer 39

- indirect acid stimulation by histamine release by ECL cells - direct stimulation on parietal cells - epithelial cell proliferation in stomach, small intestine, colon

Question 40

What stimulates gastrin secretion by G cells into the blood to circulate to ECL and parietal cells?

Answer 40

dissension of stomach and stimulation by nutrients [peptides and amino acids]

Question 41

What is the main inhibitor of acid secretion? produced where?

Answer 41

somatostatin produced in pyloris by D cells [can act directly and indirectly]

Question 42

What is the most potent inhibitor of acid secretion pertaining to food in the duodenum?

Answer 42

fat [acid and hyperosmolarity are the other 2]

Question 43

What is the major hormone involved in feedback inhibition of acid production? what does it do [3 things]?

Answer 43

secretin-- decreases gastrin release,promotes somatostatin release, and directly inhibits acid release [others are CCK, vasoactive intestinal peptide, gastric inhibitory peptide, neurotensin, peptide YY]

Question 44

When is acid secretion lowest?

Answer 44

basal state- in the morning before awakening

Question 45

What what phase of acid secretion is described by the following--thinking, seeing, smelling, tasting food? what percentage of acid secretion does it produce? What nerve mediates?

Answer 45

cephalic phase 30% vagus nerve

Question 46

The cephalic phase has 4 effects on cells, what are they?

Answer 46

parietal cell stimulation ECL stimulation G cell stimulation inhibition of somatostatin secretion

Question 47

The gastric phase entry of food has two major effects that stimulate acid secretion and produce 50-60 % of the acid secretion levels, what are they?

Answer 47

1. stomach wall stretching-->vagus and local ENS nerves | 2. protein fragments stimulate G cells

Question 48

What is the major mediator of gastric phase acid secretion?

Answer 48

gastrin

Question 49

What is activated in very low pH conditions in the stomach?

Answer 49

D cells---> somatostatin secretion

Question 50

What are the 2 types of pepsinogen? what are they secreted by? which one is more dominant?

Answer 50

Type I--chief cells--dominant | Type II--chief and mucous neck cells

Question 51

What activates secretion of pepsinogen by chief cells?

Answer 51

ACh [secretin may have role too]

Question 52

What is pepsinogen activated by

Answer 52

pH less than 5

Question 53

What are the 3 components of the gastric diffusion barrier?

Answer 53

tight junctions mucous gel layer bicarb rich secretions under mucous

Question 54

what is a glycoprotein secreted by numerous mucous cells in the stomach and located on surface epithelium?

Answer 54

Mucin--when hydrated it forms mucus

Question 55

Why does the mucus gel layer need to be constantly renewed?

Answer 55

damaged by food,

Question 56

What is release of bicarb and mucin by stomach epithelial cells stimulated by?

Answer 56

ACh

Question 57

What doe bicarb also protect cell from besides stomach acid?

Answer 57

pepsin---inactivates it