Stomach Flashcards
Diff. between deep layer cells of the mucosa in the proximal vs. distal stomach?
Proximal stomach contains acid-secreting cells:
- Chief cells
- Parietal cells
- Enterochromaffin-like cells (ECL)
Distal stomach contains neuroendocrine cells that secrete regulatory peptides:
- Gastrin
- Somatostatin
- Glucagon
Difference between muscular layer in stomach vs. esophagus?
Stomach has a 3rd layer of oblique fibers that provide more muscular support for the function of the organ
During meals, the ____ nerve seems to promote receptive relaxation of the proximal stomach, gastric acid secretion and the grinding and mixing of food with gastric acid secretion in the distal stomach
Vagus
What is the process called that relaxes the proximal stomach to enable it to accommodate food and allow it to promote its storage without raising intra-gastric pressure?
Receptive Relaxation
What 4 things does the stomach secrete during meals?
For each, give the cell that secretes it & where in the stomach these cells are located.
- Hydrochloric (Gastric) Acid
- Parietal cells in proximal stomach (active energy-dependent; H/K+ATPase) - Intrinsic factor
- Parietal cells in proximal stomach - Pepsinogen
- Chief cells in proximal stomach - Mucus
- Mucous cells in all parts of stomach
Hydrochloric (Gastric) Acid: Function?
Activated by? Inhibited by?
Fx:
- Activates pepsinogen –> pepsin
- Breaks down proteins
- Provides a protective barrier against ingested microorganisms
Activated by:
- Gastrin
- Acetylcholine
- Histamine
Inhibited by:
- Somatostatin
Intrinsic Factor: Function?
Binds vitamin B12 to form a complex that can be absorbed in the terminal ileum
Pepsin: Function? Activated by?
Fx:
- Breaks down protein for digestion
Activated by:
- Gastric acid (pepsinogen –>
pepsin)
Mucus: Function in stomach?
It consists of a glycoproteins and mucopolysaccarides that form a thin gel lining the stomach and protecting it from digestion by pepsin and acid injury
What is the inter-digestive migrating motor complex (IMMC)?
Periodic bursts of peristalsis that occur every 90 minutes between meals.
It is triggered by Motilin, which is released during long periods of inactivity (fasting).
(this results in the emptying of large indigestible solids, bacteria and debri, getting the stomach empty and ready for the next meal)
When are UGI series used?
- Detection of mucosal lesions such as ulcers or cancers
- They’re less sensitive than endoscopy, but also less invasive (still at times used)
When are CT scan, MRI, & endoscopic ultrasonography (EUS) used on the stomach?
Evaluation & staging of malignant gastric disorders
Name of procedure?
Patients are fed a test meal that is labeled with radioactive technetium. They are then scanned to determine the emptying rate of the stomach using a gamma camera.
Radionuclide Gastric Emptying Scan
Which test is the most commonly used to evaluate gastric motility disorders?
Radionuclide Gastric Emptying Scan
(patients are fed a test meal labeled w/ radioactive technetium, then scanned to determine emptying rate of the stomach using a gamma camera)
What is “Dyspepsia”
A term for epigastric pain associated with peptic injury of the stomach
- Burning discomfort
- Relieved by ingestion of foods or antacids
- May also present w/ nausea, w/ or w/out vomiting, early satiety, or postprandial fullness
What might upper GI
bleeding represent?
- Peptic ulcer disease
- Neoplastic disorders:
- - Polyps
- - Adenocarcinoma
- - Lymphoma
- - Carcinoid
- - Gastrointestinal stromal tumors (GIST)
Where in the stomach do ulcers usually form?
Antrum (specifically @ junction w/ fundus)
- normally lined by columnar epithelium that does not secrete acid
- suggests non-acid secreting cells are more susceptible to ulceration
When are Fasting Serum Gastrin Levels useful for diagnosis?
In evaluating hypergastrenimic states associated with peptic ulcer disease such as suspected:
1) Gastrinoma (Zollinger-Ellison syndrome)
2) Retained antrum syndrome, following antrectomy
3) G cell hyperplasia
Dyspepsia: first dDx thoughts?
- Acute gastritis
- Chronic gastritis (H pylori, autoimmune)
- Complications of chronic gastritis:
peptic ulcer disease - Hypertrophic gastropathies
- Gastroparesis (motor disorder)
Acid-secreting cells of the stomach are located where w/in the stomach?
Fundus & body
(parietal cells)
Symptom presentation of gastric vs. duodenal ulcers?
Gastric:
- More severe pain, soon after meals
- Less frequent relief by antacids or food
- Older patient
- Lower gastric acid levels
- (ass’d w/ risk of gastric cancer)
Duodenal:
- Pain/discomfort 3-5 hrs after meals or on empty stomach, also during night @ peak acid secretion (11p-2a)
- Younger age patient
- higher gastric acid levels
- (also no risk of gastric/duodenal cancer)
Likely explanation for ulcers formed in acid-secreting parts of the stomach?
Infection (H. pylori) can cause atrophy of acid- secreting cells, leaving the region susceptible to ulceration once they’re gone
Major worldwide cause of Peptic Ulcer Disease?
H. pylori infection
Most frequent site of duodenal ulcer?
Duodenal bulb or pyloric channel crossing into the bulb
(aka close to the stomach)
Are duodenal ulcers typically single or multiple?
Single
(multiple or large ulcers prompt an investigation for other causes, like Zollinger Ellison Syndrome)
T or F?
Up to 40% of patients w/ healed ulcers (on endoscopy) will have persistent symptoms.
True
Describe the host immune response to H. pylori infection.
(or at least that which is linked to disease & possible progression to cancer)
Th1 immune response, specifically with elevated levels of IL-1, TNF-alpha, & low levels of IL-10
Following H. pylori infection, inflammatory cells trigger the Fas Ag/CD95 pathway, which has what direct effect on the stomach?
Triggers apoptosis of gastric mucosal cells – parietal & chief cells are most susceptible
(“how does H. pylori cause infection?”)
H. pylori infection: Symptoms/presentation?
Most asymptomatic or w/ mild symptoms. Those w/ symptoms, have:
- Dyspepsia (40-50%)
- Ulcer disease (20-30%)
- Gastric adenocarcinoma (<1.0%)
Risk factors for GI toxicity due to NSAIDs?
History of Ulcers = most important! Others:
- Dose
- Duration
- Age >75
- Co-morbidity (esp. cardiovascular)
- Concurrent use of: Steroids, Anticoagulants, Aspirin, Alendronate, Clopidogrel
Ulcer complications?
- Bleeding
- Perforation
- Obstruction
- Penetration into surrounding organs (most notably a DU penetrating into the pancreas)
How do penetrating ulcers typically present?
A shift from the typical vague visceral discomfort to a more localized and intense pain that radiates to the back and is not relieved by food or antacids
The sudden development of severe, diffuse abdominal pain in a patient with a GI ulcer may indicate ______
perforation