- The food that we eat undergoes digestion, which starts in the mouth. Our mouths chew the food, and saliva is mixed into it. With the salivary enzymes facilitating chemical digestion and manual digestion from the teeth, the food turns into a bolus, a small, wet, ball-like mixture of food and saliva. When swallowed, the tongue pushes it down the esophagus, where it’s propelled into the stomach. In the stomach, the bolus is churned by muscles, aided by the release of bile and enzymes breaking it down to a semi-fluid mass called chyme. As it continues down the small intestine, it becomes liquid for more efficient absorption. When it reaches the large intestine, water is absorbed, turning it into stool or solid waste.
- Absorption happens in the intestines; however, it starts in the mouth as saliva is mixed with the food. Saliva contains amylase, a digestive enzyme that breaks down starch or carbohydrates. As the food is propelled into the stomach, it’s mixed and churned with gastric juice containing acid and digestive enzymes that break down proteins and some fats. It then passes through the small intestine, where additional fat is broken down and most of the nutrients are absorbed. Around 90% is absorbed here with carbohydrates, fats, minerals, proteins, and vitamins mostly absorbed by the jejunum. The large intestine, on the other hand, absorbs water, salts, and some of the remaining nutrients unabsorbed previously. Working with the intestines, the circulatory system is then responsible for passing the absorbed nutrients throughout the parts of the body.