Digestive System Function

Stomach Function in Digestion

• Mechanical Breakdown of food through muscle contractions.
• Denaturation of Proteins by Hydrochloric acid (HCl).
• Microbial Control: HCl kills microbes in food.

Stomach Muscles

• Oblique Muscles: Help churn food, mixing it with digestive juices to form chyme.
• Smooth Muscles: Assist in motility and mechanical processing of food.

Digestive Juices

• Hydrochloric Acid: Responsible for protein denaturation, microbial killing, and activating digestive enzymes.
• Digestive Enzymes: Proteins like pepsin activated by HCl, essential for protein digestion.
• Gastric Juice Secretion: Stimulated by the presence of food and regulated by neural and hormonal signals.
  • Neural Regulation: via Vagus nerve (parasympathetic) increases secretion; sympathetic decreases it.
  • Hormonal Regulation: Gastrin hormone stimulates secretion.

Mucosal Protection

• Mucus Production: Protects stomach lining from acid and digestive enzymes.
• Role of Chief Cells: Produce pepsinogen, converted to pepsin by HCl.

Disorders of the Stomach

Gastritis

• Inflammation: Of the stomach lining which can lead to various digestive issues.
• Causes: Infection, excessive alcohol, chronic use of NSAIDs, stress, etc.

Gastric Ulcers

• Caused by erosion of the stomach lining.
• Commonly linked to Helicobacter pylori infection.
• Treatment often involves antibiotics and acid-reducing medications.

Peptic Ulcers

• Effect: Can occur in the stomach or upper part of the small intestine.
• Often a result of H. pylori infection or prolonged NSAID use.

Vitamin B12 and Intrinsic Factor

• Intrinsic Factor: Glycoprotein necessary for Vitamin B12 absorption in the small intestine.
• Deficiency: Leads to anemia and other neurological issues.
• Sources: Mainly from fortified foods and supplements.

Regulation of Gastric Activity

Phases of Gastric Secretion

• Cephalic Phase: Triggered by the thought, sight, smell of food, stimulating gastric juice production.
• Gastric Phase: Activated by the actual presence of food in the stomach, increasing secretion of gastric juices.
• Intestinal Phase: Begins when chyme enters the small intestine, involves feedback mechanisms to regulate further secretion.

Key Hormones

• Gastrin: Stimulates HCl production and gastric motility.
• Somatostatin: Inhibits gastric secretion, balancing the digestive process.