158. The Stomach & Small Intestines | H. Pylori Infection & Symptoms, Gastric Acid Regulation & Secretion, and a Brief Discussion on Small Intestinal Bacterial Overgrowth

In this episode, we discuss the anatomy and physiology of the stomach and its unique epithelial structure. We dive into the pathophysiological implications of conditions such as Helicobacter pylori infection and hypochlorhydria, examining how they disrupt gastric function and microbial balance. Finally, we connect these concepts to the small intestine, discussing possible downstream effects of altered gastric acid secretion, focusing on microbial colonization and contributions to broader gastrointestinal health challenges, such as small intestinal bacterial overgrowth (SIBO).

Topics:

• 1. Introduction

  • Highlighting the stomach and anatomy.
  • Discussion on H. pylori.
  • Interplay between the stomach and small intestines, focusing on microbial balance and overgrowth.

• 2. Anatomy of the Stomach

  • The stomach as a hollow, muscular organ located between the esophagus and small intestine.
  • Anatomical regions: cardia, fundus, body, and pylorus.
  • Layers of gastric mucosa: epithelial lining, lamina propria, and thin band of smooth muscle.

• 3. Epithelial Lining and Specialized Cells

  • Mucous cells:
  • Location within the surface epithelium and gastric pits.
  • Secretion of viscous mucus containing mucins, forming a protective barrier.
  • Role in shielding the epithelial lining from acidic gastric juices and creating a neutral microenvironment.
  • Parietal cells:
  • Location in the gastric glands, predominantly in the fundus and body.
  • Secretion of hydrochloric acid (HCl) for digestion and defense.
  • Production of intrinsic factor and vitamin B12 absorption.
  • Chief cells:
  • Secretion of pepsinogen, converted to pepsin for protein digestion.
  • Production of gastric lipase for lipid digestion.
  • Enteroendocrine cells:
  • Hormone secretion.
  • Gastrin, acid secretion and gastric motility.

• 4. Protection and Functionality of Gastric Mucosa

  • Physical and chemical barriers.
  • Acidic environment maintained by parietal cells for enzymatic activity and pathogen defense.
  • Coordination of cell functions for efficient digestion and protection.

• 5. Transition from Stomach to Small Intestine

  • Anatomical junction marked by the pyloric sphincter.
  • Balancing the acidic environment of the stomach with the intestinal conditions.
  • Differences between stomach and intestinal epithelial barriers.

• 6. Microbial Communities in the Stomach and Intestines

  • Limited microbial diversity in the stomach due to its low pH.
  • Acid-resistant populations such as H. pylori and their impact on microbial diversity.
  • H. pylori , chronic gastritis, ulcers, and gastric lining atrophy.

• 7. H. Pylori Infection and Symptoms

  • Symptoms, manifestations.

• 8. Low Stomach Acid (Hypochlorhydria)

  • The role of stress, aging, and infections.
  • Downstream effects, particularly in the development of small intestinal bacterial overgrowth (SIBO).

• 9. Small Intestinal Bacterial Overgrowth (SIBO)

  • Definition and microbial population thresholds.
  • Protective mechanisms regulating bacterial density in the small intestine.
  • Role of low stomach acid in bacterial colonization and overgrowth.
  • Consequences of SIBO, including symptoms and metabolic activity of overgrown bacteria.