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Phys Phinal (Annie & Lauren) 💩🚽 > Gastric Secretion And Emptying > Flashcards

Gastric Secretion And Emptying Flashcards

1
Q

How many muscle layers does the stomach have?

A

3

Outer longitudinal

Middle circular

Inner oblique** unique to stomach :)

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2
Q

How does the orad stomach know to relax when food is on its way down your esophagus?

A

Via receptive relaxation, a vagovagal reflex**

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3
Q

What does the size of the stomach depend on?

A

Volume of the contents

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4
Q

What is a vagovagal reflex?

A

A reflex in which the afferent AND efferent signals are both carried by the vagus nerve

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5
Q

What happens to your vagovagal reflexes if you cut you vagus nerve>

A

No more

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6
Q

What kind of cells are in the gastric pits?

A

Parietal cells

Chief cells

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7
Q

What part of the stomach has gastric pits (with parietal and chief cells)?

A

Body

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8
Q

What part of the stomach are G cells and Mucous cells?

A

Antrum

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9
Q

What do Parietal cells secrete**

A

HCl

Intrinsic Factor

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10
Q

What do chief cells secrete?

A

Pepsinogen

“Have a Pepsi, Chief” 🥤➡️👮🏼‍♂️

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11
Q

What are the 4 major components of gastric juice?

A

HCl

Pepsinogen/Pepsin

Mucus

Intrinsic Factor

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12
Q

Is pepsinogen active?

A

No, it needs to get turned into Pepsin to be active

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13
Q

What is the only thing that the stomach secretes that we can not live without?

A

Intrinsic Factor (if you lose that part of your stomach , you need B12 injections)

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14
Q

What are the functions of HCl?

A

Reduces pH

Activates pepsin

Protein digestion

Kills bacteria

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15
Q

What does pepsin do?

A

Digests proteins

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16
Q

What does mucus do for the stomach?

A

Protects the gastric mucosa from the corrosive actions of HCl

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17
Q

What does Intrinsic Factor do?

A

It is necessary for the absorption of vitamin B12

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18
Q

How are H+ and HCO3- formed inside parietal cells?

A

Hydration of CO2 by Carbonic Anhydrase

H2O+CO2= HCO3- + H+

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19
Q

After Carbonic Anhydrase makes H+ and HCO3-, where do they each go/

A

HCO3- goes into the blood in exchange for a Cl-

H+ goes into the stomach in exchange for a K+

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20
Q

What is the alkaline tide?

A

The flow of HCO3- out of the parietal cells when they make H+

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21
Q

How does H+ get out of the parietal cell and into the stomach?

A

In exchange for K+ via ATPase

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22
Q

How does Cl- get out of the parietal cell and into the stomach?

A

Passively through chloride channels

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23
Q

What are the functions of Gastrin?

A

Stimulate Acid and pepsinogen secretion (mostly acid)

Growth of gastric and intestinal mucosa (trophic effects**)

Antral and intestinal motility

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24
Q

If you have too much gastrin what happens to the thickness of the stomach?

A

Stomach and intestine mucosa grow too thick, plus there will be a lot of acid

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25
Q

What stimulates G cells to release Gastrin?

A

Small peptides/amino acids in stomach

Distention of stomach

Vagal stimulation

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26
Q

What inhibits the release of Gastrin?

A

Low pH (don’t need any more acid!)

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27
Q

What are the 2 ways that gastrin can communicate with parietal cells

A
  1. Bind to ECL -> releases histamine -> histamine binds to H2 receptor on parietal cell
  2. Gastrin can just bind directly to a CCKb receptor on the parietal cell
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28
Q

What do ECL cells do?

A

When gastrin binds to ECL, ECL releases histamine* which then will bind to an H2 receptor** on the parietal cell and stimulate acid production.

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29
Q

How does ACh released from the vagus nerve affect parietal cells?

A

ACh will bind to an M3 receptor and stimulate acid production
(Parasympathetic stimulation, anyone?)

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30
Q

What two things can inhibit the release of HCl from the parietal cell?

A

PGE2

Somatostatin

31
Q

What is the cephalic phase of HCl secretion?

A

Influence that comes from your head (tasting, smelling, chewing, swallowing food)

32
Q

How does the signal get to your stomach to tell it to secrete HCl when you smell a juicy burger cooking?

A

Vagus nerve directly stimulates parietal cells

OR

PNS stimulates G cells to release gastrin, which will enter the circulation, and then influence Parietal cells

33
Q

What % of total HCl release is due to the Cephalic phase?

A

30%

34
Q

What neurotransmitter is released by the PNS onto G cells to tell them to release gastrin?

A

GRP (Gastrin releasing peptide)

35
Q

What are the primary stimulatnts of HCl release in the Gastric Phase of HCl release?

A

Amino acids

Small peptides (via G cells)

Distention of stomach

36
Q

How does distention stimulate HCl secretion?

A

LOCAL reflex arc- reflex is in the wall of the stomach

AND

Vagovagal reflex arc- vagus detects distention and then loops back around to tell it to release HCl

**** he talked about this A LOT

37
Q

How does Histamine stimulate HCl release?

A

Binds to H2 receptors on parietal cells

38
Q

What does cimetidine do?

A

Blocks H2 receptors on parietal cells = histamine cant bind and cause HCl release

39
Q

What % of total HCl release is due to the Gastric phase?

A

60% (main influence of HCl secretion)

40
Q

What do alcohol and caffeine do to HCl release?

A

Stimulate it

41
Q

What causes pepsinogens to become active?

A

Acid as well as autocatalysing each other once active (pepsin directly activates pepsinogen)

42
Q

What is the optimum pH for Pepsin?

A

1.5-2.0

43
Q

At what pH is pepsin denatured?

A

7.0

44
Q

What is the function of pepsin?

A

Cleaves proteins to peptides at aromatic links

digests 10-20% protein in a typical meal (most will be done in duodenum)

45
Q

What is most important for the release of pepsinogen:
Cephalic phase

Gastric phase

A

Cephalic phase*****🧠

46
Q

What stimulates the release of pepsinogen from chief cells?

A

Vagus nerve stimulation (cephalic phase)

Luminal HCl locally will stimulate release

Gastrin and secretin stimulate release

47
Q

What is the primary barrier for gastric mucosa from acid, enzymes, and physical damage?

A

Mucus

48
Q

What cells secrete mucus?

A

Mucous neck cells

Surface epithelium

49
Q

What is gastric mucus made up of?

A

Mucins (glycoproteins)

High bicarbonate levels***

50
Q

What stimulates mucus and Bicarb secretion?

A

PNS (vagus)

Gastric distention

Prostaglandins*****

51
Q

Why do NSAIDs lead to ulcers?

A

NSAIDs= no prostaglandins= less stimulation to secrete mucus and bicarbonate

52
Q

How does pH change across the mucus layer from the lumen to the gastric epithelial cells?

A

pH is ~2.0 in the lumen

~7.0 at the surface of gastric epithelial cells

53
Q

What are 4 things that protect the gastric mucosal barrier?

A

HCO3- and mucus

Prostaglandins

Mucosal blood flow

Growth factor

54
Q

What are 6 things that are damaging to the gastric mucosal barrier

A

H+ and pepsin

H pylori

NSAIDs**

Stress

Smoking

Alcohol

55
Q

What are the 3 components of gastric motility?

A
  1. Relaxation of orad stomach to accept food from esophagus (receptive relaxation. Vagal reflex involving VIP)
  2. Mixing motions to reduce size of bolus
  3. Propulsion of chyme through pyloric valve into duodenum
56
Q

What factors will increase gastric motility and emptying?

A

PNS stimulation

Gastric distention

Gastrin

Motilin(released in interdigestion periods as a housekeeping hormone)

57
Q

Are gastrin and motilin ever present at the same time?

A

No

Gastrin is released during actual digestion

Motilin is released in interdigestion periods

58
Q

What factors decrease gastric mixing and emptying?

A

SNS stimulation

Secretin, CCK and GIP (from duodenum)

H+, digestion products of fat/protein in the duodenum, duodenal distention

(Basically things that mean food is in the duodenum now and the stomach needs to calm tf down while the duodenum works on the food before the stomach squirts more in)

59
Q

What kind of reflex tells the stomach to hit the brakes for a minute before it squeezes more food into the duodenum?v

A

Enterogastric reflex- (a nervous, not hormonal signal)

60
Q

Is the pyloric valve a wide opening or very narrow?

A

Very narrow. Only VERY small particles can pass into the duodenum

61
Q

What drives the bolus toward the pyloric valve?

A

Antral peristaltic waves

62
Q

What happens if the stomach tries to push food particles that are too big through the pylorus?

A

They get reflected back into the antrum via retropulsion so that the stomach can churn them more into smaller pieces

63
Q

What 3 things will the duodenum release into the blood when its full of food to tell the stomach to hit the brakes?

A

Secretin

CCK

GIP

64
Q

What are some of the things that can cause you to vomit?

A

Stomach stretch and inflammation

Rotation (seasickness etc)

Inreacranial pressure

Pain

Smells/touches

Visual stimuli

Pregnancy

Medications

Toxins

65
Q

What muscles will be RELAXED during vomiting?

A

Stomach !!*

Esophagus

Lower esophageal sphincter

66
Q

What is the order of events when your vomiting reflex is triggered?

A

Diaphragm lowers to just above stomach

Glottis closes

Abdominal muscles contract to increase intra-abdominal pressure

Stomach, esophagus, and LES relax

Stomach gets squeezed between your diaphragm and viscera like a tube of toothpaste

UES relaxes, vomit projected into mouth

🤮

67
Q

What prevents aspiration of vomit when you’re vomiting

A

Closed glottis

68
Q

What causes Peptic Ulcer Disease?

A

Excess acid secretion

Damage to mucosa barrier

69
Q

What can cause damage to the mucosal barrier/

A

Acid-destroys mucosal cells and liberates histamine

Hitramine- stimulates more acid secretion, vasodilation, increases capillary permeability and edema

70
Q

How do you treat H pylori?

A

Clarithromycin, amoxicillin

Dont know if this is important

71
Q

Name 2 H2 blockers

A

Cimetidine (Tagamet)

Ranitidine (Zantac)

72
Q

Name 2 proton pump inhibitors?

A

Omeprazole (Prilosec)

Lansoprazole (Prevacid)

73
Q

What does colloidal bismuth (Pepto Bismol) do to your stomach?

A

Coats and protects ulcers

74
Q

What proton pump is inhibited by PPIs like omeprazole?

A

The ATPase that pumps H+ into the stomach in exchange for one K+ (on a parietal cell)

Phys Phinal (Annie & Lauren) 💩🚽 (4 decks)

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