Physiology of Digestion and Absorption of Nutrients

Function of the Small Intestine in Nutrient Absorption

The small intestine plays a crucial role in digesting and absorbing nutrients. It is divided into three sections: the duodenum, jejunum, and ileum, each contributing uniquely to the absorption of essential biomolecules.

Structure and Function of the Small Intestine

The small intestine is lined with villi and microvilli, which significantly increase the surface area for absorption. These specialized structures facilitate the uptake of nutrients such as carbohydrates, proteins, and lipids.

Absorption Mechanisms

• Carbohydrates: Digested into monosaccharides and absorbed via active transport and facilitated diffusion.
• Proteins: Broken down into amino acids and absorbed primarily through secondary active transport.
• Lipids: Emulsified by bile salts and absorbed via passive diffusion into the lymphatic system.

Role of Enzymes and Hormones

Digestive enzymes such as amylase, proteases, and lipases aid in the breakdown of macronutrients, while hormones like cholecystokinin (CCK) and secretin regulate digestive processes.

Clinical Implications

Disorders affecting nutrient absorption, such as celiac disease and Crohn’s disease, can severely impact overall health. Early diagnosis and intervention are key to managing these conditions effectively.