USMLE Guide: Gastric Glands

Introduction

The article "Gastric Glands" provides an overview of the structure and function of gastric glands in the human stomach. Understanding gastric glands is crucial for medical professionals, especially for those preparing for the United States Medical Licensing Examination (USMLE). This guide aims to summarize the key points from the article to help you effectively review this topic.

Structure of Gastric Glands

1. Location: Gastric glands are found in the gastric mucosa of the stomach.
2. Types of Gastric Glands:
   • Cardiac Glands: Located in the cardiac region of the stomach, these glands secrete mucus and are responsible for protecting the stomach from acid reflux.
   • Fundic Glands: Found in the fundus and body of the stomach, these glands produce gastric acid, pepsinogen, and intrinsic factor.
   • Pyloric Glands: Located in the antrum and pyloric region, these glands secrete mucus and gastrin.

Cell Types in Gastric Glands

1. Parietal Cells:
   • Location: Mainly found in the fundic glands.
   • Function:
     • Secrete hydrochloric acid (HCl) to maintain the acidic environment of the stomach.
     • Produce intrinsic factor, essential for vitamin B12 absorption in the small intestine.
2. Chief Cells:
   • Location: Predominantly present in the fundic glands.
   • Function:
     • Synthesize and release pepsinogen, an inactive precursor of the enzyme pepsin.
     • Pepsinogen is activated by the acidic pH and converted to pepsin, which aids in protein digestion.
3. Mucous Neck Cells:
   • Location: Located in the neck region of gastric glands.
   • Function:
     • Produce and secrete mucus, which forms a protective barrier for the gastric mucosa against acid and digestive enzymes.
4. G Cells:
   • Location: Primarily found in the antrum of gastric glands.
   • Function:
     • Synthesize and release gastrin, a hormone that stimulates gastric acid secretion and enhances gastric motility.

Regulation of Gastric Secretion

1. Gastric Phase:
   • Stimuli:
     • Distension of the stomach by food.
     • Activation of stretch receptors.
   • Effect on Gastric Secretion:
     • Increased gastric acid and pepsinogen secretion.
     • Enhanced gastric motility.
2. Cephalic Phase:
   • Stimuli:
     • Sight, smell, taste, or thought of food.
     • Activation of the vagus nerve.
   • Effect on Gastric Secretion:
     • Increased gastric acid and pepsinogen secretion.
     • Enhanced gastric motility.
3. Intestinal Phase:
   • Stimuli:
     • Presence of acidic chyme in the duodenum.
     • Activation of enteroendocrine cells.
   • Effect on Gastric Secretion:
     • Inhibition of gastric acid and pepsinogen secretion.
     • Delayed gastric emptying.

Clinical Significance

1. Gastric Acid Hypersecretion:
   • Conditions such as Zollinger-Ellison syndrome can lead to excessive gastric acid secretion, causing peptic ulcers and gastroesophageal reflux disease (GERD).
2. Gastric Acid Hyposecretion:
   • Conditions like pernicious anemia can result in decreased gastric acid secretion due to autoimmune destruction of parietal cells, leading to malabsorption of vitamin B12.
3. Gastric Mucosal Protection:
   • The mucus produced by gastric glands plays a crucial role in protecting the gastric mucosa from the corrosive effects of gastric acid and digestive enzymes.
4. Gastric Gland Pathologies:
   • Disorders affecting gastric glands, such as chronic gastritis or gastric adenocarcinoma, can have significant clinical implications and require appropriate diagnosis and management.

Remember to refer to the original article for a more comprehensive understanding of gastric glands. Good luck with your USMLE preparation!