Final answer:
Ingestion is the process of taking in food through the mouth, and plays a role in breaking down large food particles. In the absorption of nutrients, transport mechanisms at the surface of enterocytes play a key role, including the emulsification of dietary fats for absorption.
Step-by-step explanation:
Ingestion is the process of taking in food through the mouth. In vertebrates, the teeth, saliva, and tongue play important roles in mastication (preparing the food into bolus). While the food is being mechanically broken down, the enzymes in saliva begin to chemically process the food as well. The combined action of these processes modifies the food from large particles to a soft mass that can be swallowed and can travel the length of the esophagus.
Most nutrients are absorbed by transport mechanisms at the apical surface of enterocytes. With the help of bile salts and lecithin, the dietary fats are emulsified to form micelles, which can carry the fat particles to the surface of the enterocytes. There, the micelles release their fats to diffuse across the cell membrane. The fats are then reassembled into triglycerides and mixed with other lipids and proteins into chylomicrons that can pass into lacteals.