1. How does the food change in consistency and form?
The oral cavity, through chewing and hydrolysis, breaks down food physically and enzymatically, turning it into bolus, a sphere of digested food. Food, now bolus, is then propelled into the stomach by the esophagus. The stomach further breaks down the food through churning and hydrolysis. While stored in the stomach, the bolus is transformed into chyme, a more fluid, heavy cream-like substance that may be passed on to the small intestines where hydrolysis and absorption of nutrients take place. It is stored in the colon until it is passed onto the rectum and eventually, the anus, once it is ready for expulsion.
2. How could the body absorb the nutrients form the food we eat?
From the oral cavity through the small intestine, each and every chemical and mechanical stages of digestion aim to transform food into forms that may enter the blood and lymphatic capillaries. Depending on the kind of food we eat, different kinds of absorption methods take place for different nutrients. The large and small intestines are crucial for the absorption of vital nutrients. Water and digestive byproduct absorption takes place in the small intestine. In the meantime, most of the residual water, certain ions, and the vitamins K and B can only be absorbed by the large intestine. Active transport is how most nutrients are absorbed. Conversely, lactase facilitates the diffusion-based absorption of lipids. Osmosis, on the other hand, is the mechanism by which water is absorbed while pinocytosis is responsible for the absorption of large molecules.