Where does mastication, the process of chewing, primarily occur?

Mastication is the mechanical process of breaking down food into smaller pieces through the action of the jaw and teeth, which primarily takes place in the mouth. This initial phase of digestion is crucial as it increases the surface area of the food, making it easier for enzymes in saliva to begin the chemical digestion process. The teeth play a vital role in this process, as they are adapted to different types of food, allowing for effective grinding and tearing. The saliva released during mastication also helps to moisten food, making it easier to swallow and facilitating further digestion in the digestive tract.

The other options pertain to different parts of the digestive system where no chewing occurs. The oesophagus primarily functions as a passage for food to travel from the mouth to the stomach. The stomach is involved mainly in mixing and digesting food once it has been swallowed, while the intestines are responsible for nutrient absorption and further digestion, following the stomach.