Intestinal

The intestinal tract is a component of the digestive system, a long muscular tube that extends from the pyloric sphincter to the anus. It is divided into the small and large intestines. The inner surface is lined with mucosa that forms folds, villi, and microvilli to increase surface area. The enteric nervous system coordinates motility, and the gut is also influenced by the autonomic nervous system and various hormones.

The small intestine measures about 6 meters and comprises the duodenum, jejunum, and ileum. It is the primary site of chemical digestion and nutrient absorption. Pancreatic enzymes and bile aid digestion; carbohydrates, proteins, fats, vitamins, and minerals are absorbed across the mucosa. The surface area is expanded by villi and microvilli, and fats are absorbed into lymphatic vessels called lacteals.

The large intestine includes the cecum, colon, and rectum. It reabsorbs water and electrolytes, forms stool, and stores it until defecation. The colon hosts a diverse microbial community that ferments indigestible carbohydrates, producing short-chain fatty acids and gases; microbes also participate in vitamin synthesis and immune interactions.

Immune and regulatory functions are supported by gut-associated lymphoid tissue and other immune cells that monitor intestinal contents and maintain the barrier between the interior of the body and the external environment. Normal function supports digestion, nutrient uptake, and overall gut health; dysfunction can be involved in conditions such as inflammatory bowel disease, celiac disease, irritable bowel syndrome, infections, obstruction, or malabsorption.