What happens in small intestine?

The small intestine is a vital organ in the human digestive system responsible for several crucial processes related to digestion and nutrient absorption. Here's an overview of what happens in the small intestine:

1. Digestion of Carbohydrates, Proteins, and Fats:

- The small intestine receives partially digested food from the stomach.

- Enzymes secreted by the pancreas and the lining of the small intestine further break down carbohydrates, proteins, and fats.

- Carbohydrates are broken down into simple sugars like glucose, galactose, and fructose.

- Proteins are broken down into amino acids.

- Fats are broken down into fatty acids and glycerol.

2. Absorption of Nutrients:

- The inner lining of the small intestine has numerous tiny finger-like projections called villi, which increase the surface area for nutrient absorption.

- Villi contain even smaller projections called microvilli, further enhancing nutrient absorption.

- Glucose and galactose are absorbed into the bloodstream through the villi.

- Fructose is absorbed by facilitated diffusion.

- Amino acids are absorbed into the bloodstream through active transport.

- Fatty acids and glycerol are absorbed into the lymphatic system and then enter the bloodstream.

3. Emulsification of Fats:

- The gallbladder releases bile, which helps in the emulsification of fats.

- Bile salts break down large fat droplets into smaller ones, increasing the surface area for enzyme action.

4. Absorption of Water and Electrolytes:

- The remaining chyme, consisting of undigested materials and water, moves through the small intestine.

- Water is absorbed through osmosis, and electrolytes like sodium and potassium are actively transported.

5. Peristalsis:

- Peristaltic contractions occur in the small intestine, which help mix and propel the contents forward, facilitating digestion and absorption.

6. Secretion of Hormones:

- The small intestine also produces hormones that regulate digestion and metabolism, such as cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1).

After nutrient absorption is complete in the small intestine, the undigested materials and waste products pass into the large intestine for further processing and eventual elimination.