Gastrointestinal Physiology Quiz

Digestive System Diseases: Gastritis and Peptic Disease

• Gastritis is a condition where the stomach lining becomes inflamed due to various causes.
• Gastritis can be categorized as acute or chronic, based on the duration of inflammation.
• Acute gastritis involves neutrophils in the stomach lining, and can stem from conditions like extensive burns, trauma, or severe sepsis. It can also result from drug use (NSAIDs), alcohol consumption (severity depends on amount, fasting intake, and binge frequency), or exposure to caustics or radiation.
• Chronic gastritis involves monocytes, lymphocytes, and plasma cells in the stomach lining. Types include autoimmune chronic gastritis (Type A), chronic gastritis related to H. pylori infection (Type B), and bile reflux gastritis (Type C).

Stomach Anatomy and Function

• The stomach is a J-shaped organ in the upper abdomen.
• Its main functions include food storage, mixing liquefying food (chyme), and emptying chyme into the small intestine.
• The stomach has different regions (fundus, proximal part of the gastric body, distal portion of the gastric body + antrum) which each contribute to different functions, like food storage and mixing by peristaltic contractions.
• The stomach has a mucosal barrier, containing bicarbonate-rich mucus to prevent self-digestion. This barrier also contains surface mucus cells that release alkaline mucus.
• The stomach has different cell types (mucous neck cells, parietal cells, chief cells, enteroendocrine cells, etc.) that secrete different substances, including mucus, acids (hydrochloric acid), intrinsic factor, enzymes (pepsinogen), and hormones (gastrin).

Stomach Function: Secretion

• Parietal cells in the stomach secrete roughly two liters of hydrochloric acid (HCl) per day. This acid is crucial to kill bacteria, aiding digestion by solubilizing food, and establishing the proper pH environment for the function of digestive enzymes. A key protein for this process is H+/K+-ATPase (or proton pump).
• Pepsinogen is a protein-digesting enzyme produced by chief cells in the stomach. HCl converts pepsinogen to the active pepsin, and this process happens at a pH between 1.8-3.5.
• Mucus, bicarbonate, and prostaglandins are key protective components of the stomach's mucosal barrier, helping to safeguard against self-digestion damage.

Stomach Function: Motility

• Stomach motility involves rhythmic contractions of smooth muscles. It plays important functions in processing food, like mixing and grinding, and emptying into the small intestine.
• The stomach divides into two regions based on motility patterns: a reservoir and a grinder, working together to mix and mechanically process food contents for better digestion.

Helicobacter Pylori

• H. pylori is a spiral-shaped bacterium that plays a key role in gastric disease.
• It can cause chronic gastritis and is linked with both duodenal and gastric ulcers.
• The bacterium produces urease, neutralizing acids and establishing a localized neutral environment conducive to its survival and infection.
• It's also linked to precancerous conditions and gastric cancer and is the most common cause of chronic gastritis (> 90%).
• Diagnostic tests for H. pylori infection include histology, rapid urease tests, culture tests, IgG in serum, 13C Urea Breath Tests, and fecal antigen tests.

Peptic Ulcer Disease

• Peptic ulcers are open sores in the lining of the stomach or duodenum.
• Factors associated with peptic ulcer disease include infection with H. pylori and NSAID (nonsteroidal anti-inflammatory drug) use.
• Symptoms commonly include pain or burning sensation, typically after eating.
• Diagnostic tools include endoscopy and biopsies.
• Treatment often involves antibiotics and proton pump inhibitors to reduce stomach acidity and combat H. pylori infection.
• Complications can arise if left untreated and include hemorrhage, perforation, or gastric outlet obstruction.

Gastritis: Additional Considerations

• Classifications of gastritis include time-course (acute or chronic) and specific causative factors (e.g., autoimmune, H pylori, bile reflux).
• Pathological evaluation (biopsy) is essential to determine gastritis type.
• Factors influencing ulcer recurrence include treatment failure, ongoing NSAID exposure, and smoking.
• Treatment of mild or uncomplicated cases generally features proton pump inhibitors, whereas complicated ulcers might necessitate endoscopic therapy and even surgery.

Chronic Gastritis: Important Aspects

• Chronic gastritis is a prolonged condition involving inflammatory infiltration and cellular and functional damage.
• Two major types (Types A and B) are distinct in cause, manifestation, and cellular components involved in the inflammation.
• Type A is primarily autoimmune in nature, frequently involves the body and fundus of the stomach, and often relates to other autoimmune conditions.
• Type B is largely attributed to H. pylori infection and typically affects the antrum.
• Additional risk factors for chronic gastritis, are things like cigarette smoking and bile reflux.
• Diagnosis typically necessitates an endoscopy and biopsy.

Intestinal Metaplasia in Chronic Gastritis

• Intestinal metaplasia is a type of gastric mucosal change involving the replacement of gastric epithelium with intestinal-type epithelium.
• The OLGA staging system utilizes these changes, particularly intestinal metaplasia, as a diagnostic tool, aiding assessment of gastritis severity and potential cancerous risk.
• Intestinal metaplasia is a precancerous condition.

Dyspepsia

• Dyspepsia describes a complex of symptoms, often involving chronic or recurrent upper abdominal pain and/or discomfort associated with eating.
• The differentiation of the exact cause of the pain requires advanced diagnostic approaches involving multiple studies, often through endoscopy and biopsy.