GASTROINTESTINAL SYSTEM: STRUCTURE AND FUNCTIONS
The gastrointestinal (GI) system, also known as the digestive system, is responsible for breaking down food, absorbing nutrients, and eliminating waste. It consists of the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus, along with accessory organs such as the liver, pancreas, and gallbladder.
| Mouth and esophagus: | Digestion begins in the mouth, where food is chewed and mixed with saliva, containing enzymes that start breaking down carbohydrates. The chewed food, now called a bolus, is swallowed and passes through the esophagus, a muscular tube that conveys it to the stomach via peristaltic contractions. |
| Stomach: | The stomach is a muscular organ that further breaks down food using gastric juices, which contain hydrochloric acid and digestive enzymes. The acidic environment helps break down proteins and kill harmful microorganisms. The partially digested food, now called chyme, is slowly released into the small intestine. |
| Small intestine: | The small intestine is a long, coiled tube where most of the digestion and absorption of nutrients occurs. It consists of three sections: the duodenum, jejunum, and ileum. In the duodenum, chyme is mixed with bile from the liver and digestive enzymes from the pancreas, further breaking down fats, proteins, and carbohydrates. Nutrients are absorbed through the intestinal walls into the bloodstream. |
| Large Intestine and Accessory Organs: | The large intestine absorbs water and electrolytes from the remaining indigestible food matter, forming solid waste (feces) to be excreted. The large intestine includes the cecum, colon, rectum, and anus. The liver, pancreas, and gallbladder play vital roles in digestion, producing bile, enzymes, and other substances necessary for breaking down food. |