Digestive System

The digestive system, also known as the gastrointestinal (GI) tract, is a complex series of organs and structures that processes food, extracts and absorbs nutrients, and eliminates waste from the body. It includes the mouth, pharynx, esophagus, stomach, small intestine, large intestine (colon), rectum, and anus. Accessory organs, such as the salivary glands, liver, gallbladder, and pancreas, produce enzymes and substances that aid in digestion but are not part of the alimentary canal. The process begins with ingestion, where food is chewed and mixed with saliva to begin mechanical and chemical breakdown.

After initial processing in the mouth, food passes through the esophagus and into the stomach, where it is further broken down by gastric juices. The partially digested food, now called chyme, enters the small intestine, where the majority of nutrient absorption occurs through its lining into the bloodstream. The small intestine's villi and microvilli increase the absorptive surface area significantly. Any undigested residues proceed to the large intestine, where water is reabsorbed and the remaining material is formed into feces, which are ultimately expelled from the body through defecation, concluding the digestive process. The system is regulated by complex neural and hormonal mechanisms to ensure optimal function.