Term
| What is the purpose of the mesenteric membranes? |
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Definition
| Keep the stomach in place -- lesser and greater omentums |
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Term
| What is the anatomy of the stomach? |
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Definition
- Cardial stomach - portion right after the stomach. Produces ONLY mucus
- Fundus - raises up. Mucus, gastric acid, enzymes, and intrinsic factor
- Body/corpus - main part - MOST amount of gastric acid, mucus, and intrinsic factor.
- Antrum - just before pyloric. Mucus, enzymes, and the HORMONE gastrin
- Pyloric canal- empties into duodenum, ending at the pyloric sphincter. ONLY mucus.
** folds called rugae, allow for expansion |
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Term
| What parts of the stomach secrete intrinsic factor? What is it? |
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Definition
| The fundus and the body/corpus. Required for absorption of b12 |
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Term
| What is the anatomy of gastric glands? |
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Definition
- Chief cells - produce enzymes
- Parietal cells - produce acid and intrinsic factor |
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Term
| How large can the stomach expand to? |
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Definition
| Up to 4 L, expanded by chyme and gastric juice |
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Term
| What provides blood flow to the stomach? |
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Definition
Right and left gastric arteries
Right and left gastropiploid arteries
Not much nutrient absorption, what is absorbed goes to the hepatic portal vein. |
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Term
| What are the major functions of the stomach? |
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Definition
- Temporary storage of food - receptive relaxation through VIP, NO, CCK. MAIN FUNCTION
- Mechanical breakdown of PROTEINs by HCl and pepsin
- Mixing - formation of chyme
- Propulsion towards intestines
- Production of intrinsic factor |
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Term
| How is gastric emptying controlled? |
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Definition
- By BOTH stomach distention and duodenum
- Vagal PSNS stimulation increases motility
- Gastrin - slows emptying, signalled by proteins
- Enterogastrones are inhibitory - CCK, Secretin, GIP
- Duodenum has reflexes to the presence of acid, irritation, foods, and distention --> inhibition
** goal is to slow emptying, allow stomach to work longer. |
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Term
| Where is acid secreted in the stomach? |
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Definition
In the gastric lumen. Beneath that is (should be) a mucous/bicarbonate layer to protect the COLUMNAR/goblet cells of the stomach.
Goblet cells produce mucus, columnar cells produce bicarb. |
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Term
| How are parietal cells activated? |
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Definition
Activated during meals - TV turn into microvilli and intracellular canaliculus is developed. Hydrogen/potassium ATPase pump is active.
**An active parietal cell secretes acid and intrinsic factor! |
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Term
| What secretagogues are responsible for acid release? |
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Definition
- Ach -- on M3 receptors - act directly and indirectly by releasing histamine
- GASTRIN - from G cells in antrum - directly and indirectly by histamine release
- Histamine - from EC-like cells |
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Term
| What are mechanisms for direct acid release from parietal cells? |
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Definition
- Ach acts on M3 --> IP3/Calcium --> ATPase pump
- Histamine acts on H2 --> cAMP/PKA --> ATPase pump
- Gastrin acts on CCKb --> IP3/calcium --> ATPase pump |
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Term
| What are mechanisms for indirect release of acid from parietal cells? |
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Definition
| - Ach or gastrin stimulate EC-like cells to release histamine --> histamine acts of H2 receptor of parietal cell --> cAMP/PKA and activation of ATPase pump |
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Term
| What are the steps to the parietal cell forming HCl? |
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Definition
- Gastrin, histamine, or Ach directly or indirectly stimulate the cell, activating the ATPase pump
- carbonic acid breaks down bicarb into hydrogen ions.
- ATPase exchanges H/K, while and exchanger brings Cl inside the cell in exchange for HCO3-
- Chlorine and K channels exist, allowing the Cl- and K+ to leave. H+ + Cl- = ACID! |
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Term
| What are functions of high acidity in the stomach? |
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Definition
- KILL microorganisms present in food
- Denature proteins
- Break down plant cell walls
- Activation of pepsinogen released from chief cells. |
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Term
| What can inhibit secretion of acid endogenously? |
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Definition
- Prostaglandins - from stomach. reduce cAMP
- Stomatostatin - from D cells
- Enterogastrones: Secretin (S cells), CCK (I cells), GIP (K cells), VIP (enteric nerves) |
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Term
| How do infant chief cells differ from adult physiology? |
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Definition
| Pepsinogen is not produced - rennin is produced that breaks down only milk. |
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Term
| What is the only function of the stomach necessary for life? |
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Definition
| Manufacture of intrinsic factor |
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Term
| How is cobalmin handled by the stomach/small intestine? |
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Definition
- Bound to proteins in food, released in the stomach by acid.
- Parietal cells secrete intrinsic factor
- Haptocorrin binds to B12 in the stomach, prevents degradation. Removed in the small intestine
- In the small intestine, IF-B12 complex forms. B12 can now be absorbed. |
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Term
| What are the 4 phases of digestion? |
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Definition
- Cephalic phase - prepares the stomach for the arrival of food. 20% of acid secreted. Under Vagal control
- Gastric phase - 60-70% of acid. Stimulation of receptors by food. PEPSIN breaks down protein. ENS and vagovagal reflexes inhibit D cell release of somatostatin
- Intestinal phase - control rate of gastric emptying, last phase of acid release
- Interdigestive phase
**Acid is it's own negative feedback |
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Term
| What are the function of Ach in the stomach? |
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Definition
- Direct binding to parietal cell --> acid release
- Binds to M3 on chief cells - pepsinogen release
- M3 on EC-like cells - histamine release --> parietal cells
- Bind to G cells to release gastrin --> parietal cells
** Ach moderates acid cleavage of pepsinogen to pepsin! |
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Term
| What happens if acid or fat gets into the small intestine? |
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Definition
Neural response - increase in SNS, constriction of pyloric sphincter. Decrease in PNS
Release of CCK, Secretin, and GIP to slow gastric emptying.
Enhanced digestion in the STOMACH. |
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Term
| What do enterogastrones stimulate? |
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Definition
- CCK (I cells) - stimulates pancreas acinar cells and gallbladder
- Secretin (S cells) - stimulates pancreas duct and liver - bicarbonate and bile
- All 3 - Inhibits stomach release of gastrin, acid, and pepsinogen. |
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Term
| How are ghrelin levels effected by consumption of meals? |
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Definition
- Low during consumption of meals
- High during fasting
** stimulates GH secretion
** stimulates appetite |
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Term
| How does leptin control body weight? |
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Definition
Leptin is released from adipose, turns off appetite.
**More adipose, less of an appetite. |
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Term
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Definition
| Inflammation of the rugae, can be caused by H. pylori |
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Term
| What is peptic ulcer disease? |
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Definition
An ulcer in the GI tract that is usually acidic.
- Gastric ulcer - in the stomach. Usually decreased protection in MUCOSA rather than oversecretion of acid
- Duodenal ulcer - in duodenum. Increased parietal cells = increased acid/pepsin, increased SENSITIVITY to gastrin
- Esophageal ulcer - in esophagus, usually caused by GERD |
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Term
| What are the major causes of PUD? |
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Definition
- H.Pylori - more duodenal ulcers. MOST COMMON CAUSE
- Impaired mucosa - NSAIDS!, steroids, stress
- Hypersecretion - Zollinger-ellison --> elevated gastrin release |
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Term
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Definition
A lifelong infection of a bacteria that burrows into the stomach and intestinal lining. Burrows into the antrum or duodenum to protect itself from acid.
** Production of ammonia to neutralize acid
** Initiation of inflammatory response --> injection of CagA --> NFkB --> release of IL-8 attracts PMNs and release of TNF and IL-1.
** Humoral and Cellular immune rxn leads to chronic inflammation |
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Term
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Definition
- Loss of epithelial cell fxn - mitochondria uncoupling
- Inhibition of prostaglandin synthesis through COX inhibition --> decreased mucus, bicarb, and increased acid
- increased free radicals
- direct toxicity
**Attraction of NEUTROPHILS promotes inflammation |
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Term
| What is zollinger-ellison syndrome? |
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Definition
| The least common source of PUD, tumors produce excessive gastrin --> increased acid release. NO negative feedback! |
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