Physical digestion is the physical process of breaking down food into smaller pieces that can easily be accessed by digestive enzymes, without making any chemical changes, whereas chemical digestion refers to the process through which the mammalian body further breaks down food substances into small, soluble chemicals that can be absorbed into the blood. The chewing of food and movement in the stomach contribute to physical digestion while natural catalysts aid chemical digestion.
Peristalsis is an important part of physical digestion; it facilitates the muscular churning of food in the stomach and the movement of food down the digestive tract. Chemical digestion is sped up by enzymes. After the food fully digests, the molecules pass through the small intestine wall via diffusion.