Gastrointestinal Physiology Overview

Overview of Gastrointestinal Physiology

• The gastrointestinal (GI) system is responsible for the ingestion, digestion, and absorption of nutrients, as well as the elimination of waste products.
• The GI system consists of the mouth, esophagus, stomach, small intestine, and large intestine.

Motility and Movement

• Peristalsis: rhythmic, wave-like muscle contractions that propel food through the GI system
• Segmentation: localized, intermittent contractions that mix food with digestive enzymes
• Mass movement: strong, coordinated contractions that propel food through the large intestine

Digestion and Absorption

• Mechanical digestion: breakdown of food into smaller particles through chewing and grinding
• Chemical digestion: breakdown of nutrients into smaller molecules through enzymatic reactions
• Absorption: uptake of nutrients into the bloodstream through the walls of the small intestine
• Nutrient absorption sites:
  • Carbohydrates: small intestine
  • Proteins: small intestine
  • Fats: small intestine and liver

Gastric Function

• Gastric acid: secreted by parietal cells, pH 1.5-2.5, denatures proteins and activates pepsin
• Pepsin: enzyme that breaks down proteins into smaller peptides
• Gastric mixing: contractions of the stomach mix food with gastric acid and pepsin

Small Intestine Function

• Brush border enzymes: enzymes embedded in the microvilli of enterocytes, break down carbohydrates and proteins
• Pancreatic juice: alkaline fluid containing digestive enzymes, secreted by the pancreas
• Bile: emulsifies fats, secreted by the liver and stored in the gallbladder

Large Intestine Function

• Water absorption: reabsorption of water and electrolytes from the colon
• Electrolyte absorption: reabsorption of sodium, potassium, and chloride from the colon
• Feces formation: remaining waste products are formed into feces

Hormonal Regulation

• Gastrin: stimulates gastric acid secretion and gastric motility
• Cholecystokinin (CCK): stimulates pancreatic juice secretion and gallbladder contraction
• Secretin: stimulates pancreatic juice secretion and bicarbonate production
• Motilin: stimulates gastric motility and hormone secretion

This quiz covers the functions and processes of the gastrointestinal system, including motility, digestion, absorption, and hormonal regulation. It explores the roles of different organs and enzymes in the breakdown and uptake of nutrients. Test your knowledge of the GI system!