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SF3_3 (Kereen) > Littletone Part II > Flashcards

Littletone Part II Flashcards

1
Q

The gastric mucosa is compased of two functional regions, what are they?

A

Oxyntic Gland Area (85%)

Pyloric Gland Area (15%)

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2
Q

What are the anatomic areas of the Oxyntic Gland Area?

A

Cardia

Fundus

Corpus

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3
Q

What are the anatomic areas of the pyloric gland area?

A

Antrum

Pylorus

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4
Q

Where do Ulcers tend to occur?

A

Near Mucosal Junction

Esophageal Junction

Oxyntic-Antral Junction

Gastroduodenal Junction

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5
Q

What causes Esophageal Ulcers?

A

Reflux disease. Gastric content is protruded twoard the lower esophageal spincter.

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6
Q

At the Cardia of the stomach there are specialized cells, what are they?

A

Cardiac Pacemaker cells

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7
Q

What is the function of cardiac pace maker cells?

A

Change stomach general motility when they become depolarized.

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8
Q

What is the main type ulcer that is usually found?

A

Gastric Ulcer

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9
Q

Duodenal Ulcers typicaly occur at which part of the duodenum?

A

head of the duodenum

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10
Q

Surface Mucous Neck Cells

A

Secrete

Mucous

Bicarbonate

trefoil peptidase (small, on surface of epithelial cell)

Stimulus for Release

Tonic Secretion ; with irritation of mucosa

Bicarb secreted with mucus

Function of Secretion (protection and lubrication)

Physical Barrier between lumen and epithelium

Bicarb buffers gastic acid to prevent damage to epithelium

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11
Q

Parietal Cells

A

Secrete

Gastric acid (HCL) - H+

Intrinsic factor

Stimulus

Ach, gastrin, histamine

Function of secretion

Activates pepsin, kills bacteria (protein digestion)

Complexes with vitamin B12 (cobalamin) to permit absorption of iron in ileum

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12
Q

Enterochromaffin-like cell

A

Secrete

Histamine

Stimulus

Ach, gastrin

Function of Secretion

stimulates gastric acid secretion

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13
Q

Chief Cells

A

Secrete

Pepsin(ogen)

Gastric Lipase

Stimulus

Ach acid, secretin

Function of Secretion (regulation of acid secretion)

Digest proteins

Digest fats

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14
Q

D cells

A

Secretes

Somatostatin

Stimulus

Acid in the Stomach

Functionof Secretion

Inhibits gastric acid secretion

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15
Q

G cells

A

Secretes

Gastrin

Stimulus

Ach, peptides, and amino acids

Function of Secretion

Stimulates gastric acid secretion

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16
Q

Endocrine Cells

A

Product

gastrin, histamine, somatostatin

Function

Regulation of acid secretion

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17
Q

Ionic concentrations in gastric juice vary with secretory rate. Describe how Cl-, H+, K+, HCO3-, and Na+ change and gastric secretion increases.

A

Cl- and H+ increase

K+ slight increase

HCO3- mild increase

Na+ huge decrease

This all happens as gastric secretion increases

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18
Q

Describe the Gastric Acid Secretion in the Parietal Cell

A

CO2 (readily acceptable to parietal cell) + H2O -> H2CO3 -> (carbonic anhydrase) -> HCO3- + H+

Hydrogen is removed out the cell by a H+/K+ Antiport, ATP (hydrogen excreted to lumen and potassium taken into the cell.

More Potassium also gets into the cell through the Na+/K+ ATP pump

Potassium needs to get back out. Sent out through positive charge potassium channel -> Lumen

Removal of Bicarb from the cell = Cl-/HCO3- exchanger (passive). Bicarb to plasma and Cl- taken into the cell. This Cl- is then sent to the Lumen through and negative charge chloride channel.

H+ + Cl- -> HCL in the lumen = increase in acidity

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19
Q

What is Electrogenic proton transport?

A

Coupling an electroneutral H+ for K+ ATP driven exchange activity (ATP) in parallel with conductive channels for K+ and Cl-, and eddicient recycling of K+.

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20
Q

The upper gastrointestinal mucosa is covered by a layer of what?

A

Mucus

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21
Q

What is mucus?

A

A viscoelastic get that contains 85& water and 15% glycoproteins.

It slightly impedes movement from the lumen to the apical cell membrane

(HCL flow sin HCO3 flows out

It is relatively impermeable to pepsin

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22
Q

A barrier to the diffusion of H+ and pepsin covers the gastroduodenal mucosa. What is it called?

A

Mucus-Bicarbonate Barrier

H+ flows in and HCO3 flows out

Lumen ph = 1-2

Mucosa ph = 7

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23
Q

While the luminal pH may be ______, the pH at the surface cell membrane is near _______.

A

acidic

neutral

24
Q

During damage _______, _____, and other ________ _______ increase capillary filtration.

A

Histamine

Acid

Vasoactive Agents

25
Q

What occurs in the damaged area during erosion?

A

Ultrafiltrate of plasma

Edema

Protein loss

Blood loss

26
Q

Erosion occurs by?

A

Damage to the mucus protection layer of the GI

27
Q

How does hydrogen ions increase the damage in a area?

A

Hydrogen ions act on mast cells which causes them to realease PGs, Leukotrines, histamines, and chemotactic factors.

Histamine breaks down capillaries

28
Q

Polymorphonuclear (PMN_) leukocytes release?

A

These are found in the GI lining and they release leukotrines, PGs, O2 radicals, proteases, and peroxidases.

29
Q

What is H. Pylori?

A

Gram negative bacteria found in contaminated water. It goes through the mucous layer of the GI tract and sits on the basement membrane (on top of epithelium) and opens up the epithelium -> erosion

30
Q

H Pylori releases several products that may mediate local tissue injury, what are they?

A

Urease

Cytotoxins

Mucinase

Phospholipase

Platelet-activating factor

31
Q

What is the purpose of Urease secreted by H. Pylori?

A

Converts Urea -> ammonia + CO2

An ammonia cloud is created to protect H. Pylori from the acidic enviroment of the GI tract

32
Q

What is the purpose of Mucinase that is secreted by H. Pylori?

A

degrades mucous gylcoproteins

33
Q

What is the point of Phospholipdase that is secreted by H. Pylori?

A

Damages epithelial cells, mucus

34
Q

What is the effect of Platelet activating factor that is secreted by H. Pylori?

A

Mucosal injury, thrombosis in microcirculation

35
Q

What effect does H. Pylori have on D cells and Somatostatin?

A

It decreases Antral D-cells and Somatostatin, increasing gastrin and possibly acid secretion

(somatostatin is suppose to inhibit acid secretion by inhibiting the activity of G-cells. Because it is decreased G-cells are running wild -> increase in gastrin secretion -> increase in number of parietal cell and increase in gastric secretion)

36
Q

What are the three receptros found on parietal cells and what do they respond too?

A

CCKB - responds ot Gasrin

H2 = responds to histamine

M2 = responds to acetylcholine.

Alll three of these substance stimulate the release of HCL

37
Q

Parietal Cell Secretion is regulated by what?

A

Site-specific agonist and antagonist

38
Q

What is the effect of prostaglandins on parietal cells?

A

They inhibit cAMP (which is increased in response to histamine) to decrease gastric acid secretion.

39
Q

What effect does histamine have on cAMP in the parietal cell.

A

It causes a increase in cAMP which leads to acid secretion

40
Q

What is increase in the parietal cell in response to gastrin?

A

In calcium concentration which leads to increase in gastric acid secretion.

41
Q

What can be inhibited at teh apical membrane to decrease gastric acid secretion?

A

H+/K+ ATPase is used by Histamine, Gastrin, and acetycholine to get H+ ions to the lumen. A ATPase antagonist can be used to block this reaction -> decreased acid secretion

42
Q

What can be used to decrease the affect of acetycholine on parietal cells?

A

Anticholinergics

43
Q

What can be used to decrease the effect of Gastrin on parietal cells?

A

Gastrin antagonist

44
Q

What can be used to decrease the effects of histamine on the parietal cell?

A

H2 blocker

(antagonist structurally similar to histamine)

45
Q

What are examples of H2 antagonist?

A

Cimetidine (most known)

Ranitidine

Famotidine

Nizatidine

46
Q

What are the affects of Omeprazole?

A

It is a weak base (pH = 4) that concetrates exclusively in secretory canaliculus where it becomes ionized

activated at low pH to for an ative sulfur group. The sulfar group forms a covalent disulfide bond at a critical luminal site on H+/K+ ATPase

47
Q

Stimulation of Acid Secretion is divided into 4 phases, what are they?

A

Interdigestive

Cephalic

Gastric

Intestinal

48
Q

Interdigestive phase of Acid Secretion

A

Stimulus = Basal (between meals there is a small continuos amount of acid secretion)

Percent of total response = 15%

49
Q

Cephalic phase of Acid Secretion

A

Stimulus = smell, taste, and sight of food

Percent = 30%

Mediated by Vagus nerve

50
Q

Gastric phase of Acid Secretion

A

Stimulus = food in stomach

Percent = 50%

Gastrin and acetycholine are released by distention and protein digestion products

51
Q

Intestinal Phase of Acid Secretion

A

Stimulus = Digestion products in intestine

Percent = 5%

Secretion stimulated by hormones and absorbed amino acids

52
Q

Describe the mediation of the vagus nerve on the cephalic phase of acid secretion

A

sigh, smell, taste, chewing, swallowing, condition reflex -> postively stimulates vagal nucleus

Direct effect

acetycholine is released -> Oxyntic cell stimulated -> increase acid secretion

Indirect effect

Bombesin released -> stimulates G cells -> gastrin released -> this stimulates Oxyntic cell -> increase acid secretion

Vagal nucleus inhibits the somatostatin cell

53
Q

What is the autoregulation control of acid in the stomach?

A

When the stomach becomes to acidic the vagal inhibition is overcame and somatostatin cell is no longer inhibited -> somatostatin is released -> this inhibits the G cell this inhibiting gastrin release = decrease in H+ secretion

54
Q

Distention of the stomach by food caused what?

A
  1. Local reflexes -> acetycholine released -> acts on G cell (release gastrin) and Oxyntic cell -> increase H+
  2. Vaso-vagal reflex

Bombesin release -> g cell activated -> gastrin released -> act on Oxyntic cell -> increase H+ release

acetycholine - > Oxyntic cell stimulated -> increase H+ release

55
Q

What is the effect of digesiton of proteins in gastric phase?

A

Peptides and amino acids -> stimulate G cell -> gastrin (big) released -> Oxyntic cell stimulated -> H+ release

56
Q

What is the effect of digestion of proteins in the intestinal phase?

A
  1. Intestinal G cell stimulated -> big gastrin released
  2. Intestinal Endocrine cell stimulated -> Entero-oxyntin released
  3. Absorbed amino acids

All act on Oxyntic cell -> small amounts H+ released

SF3_3 (Kereen) (14 decks)

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