Physiology of the Gastrointestinal System II: Digestion and Absorption

The gastrointestinal tract extends from the mouth to the anus, facilitating both mechanical and chemical digestion.

Digestion starts by chewing food in the mouth. The chewed food, known as bolus, travels through the esophagus to the stomach for further digestion.

The stomach produces gastric secretions, like hydrochloric acid, which converts food into a semi-fluid mass called chyme.

This acidic environment activates pepsin, initiating protein digestion.

Chyme then moves to the small intestine, prompting the release of pancreatic enzymes and bile.

Bile emulsifies fat, and pancreatic amylase continues carbohydrate digestion while brush-border enzymes convert disaccharides into monosaccharides and complete protein digestion.

Next, digestion occurs in the small intestine through pancreatic lipase, breaking triglycerides into fatty acids and monoglycerides.

Finally, the small intestine absorbs end products like monosaccharides, amino acids, fatty acids, water, electrolytes, vitamins, and minerals through villi movement.