Gastrointestinal Physiology Overview

Study Notes

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

Description

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!