Gastrointestinal and Liver Disorders

Gastrointestinal and Liver Disorders

Case 1

The gastrointestinal (GI) tract is the body’s entry point for nutrients, including fluids and electrolytes needed to sustain life. Disorders of the GI tract are often grouped into the following categories: alteration of digestive function, absorptive function, immunologic function, and neuroendocrine function.

What are the stimuli to the multiple substances that control gastric acid secretion? What risks result from having strong acidity in the stomach?

What is the pathophysiology of Helicobacter pylori?

Case 2

The liver is a complex organ with many contributions to homeostasis that are often not appreciated until liver function declines. The liver has the capacity to rebound and regenerate after a variety of acute chemically or virally induced insults, but it is vulnerable to chronic chemical or infectious damage.

What blood tests are appropriate for a patient with a suspected acute liver injury?

Explain the rationale for ordering these tests, and patterns of results that you might see in a patient with acute HAV infection.

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APA

Gastrointestinal and Liver Disorders

Stimuli Controlling Gastric Acid Secretion

Gastric acid secretion in the stomach is tightly regulated by multiple stimuli, which include both neural and hormonal factors. The primary substances involved in controlling gastric acid secretion include acetylcholine, gastrin, and histamine.

1. Acetylcholine (ACh): Released from the parasympathetic vagus nerve, acetylcholine stimulates the muscarinic receptors on parietal cells to increase gastric acid secretion.

2. Gastrin: Secreted by G cells in the stomach in response to food intake (especially proteins), gastrin binds to CCK-B receptors on parietal cells, which leads to increased acid production. Gastrin also stimulates the release of histamine from enterochromaffin-like (ECL) cells, further enhancing acid secretion.

3. Histamine: Released from ECL cells, histamine binds to H2 receptors on parietal cells, resulting in increased acid secretion. This pathway is the target of H2 blockers (e.g., ranitidine), which are used to reduce gastric acid production.

Other factors, such as proteins in food, especially amino acids, and stretching of the stomach wall (distension), also play a role in stimulating gastric acid secretion.

Risks of Strong Acidity in the Stomach

Excessive acidity in the stomach can result in several health risks, including:

1. Peptic Ulcer Disease (PUD): The erosion of the stomach lining or the duodenum due to excessive gastric acid leads to ulcers. If untreated, this can result in bleeding, perforation, or obstruction.

2. Gastroesophageal Reflux Disease (GERD): Chronic acid reflux from the stomach into the esophagus can cause esophagitis, scarring, and even an increased risk of esophageal cancer over time.

3. Gastritis: Inflammation of the stomach lining, often caused by excessive acid production, leading to pain, nausea, and vomiting.

4. Bleeding: Strong acid can damage the stomach lining and cause gastric bleeding, which can be a medical emergency.

Pathophysiology of Helicobacter pylori Infection

Helicobacter pylori (H. pylori) is a…