1. In the human digestive system, the process of digestion has many stages, the first of which starts in the mouth (oral cavity). Digestion involves the breakdown of food into smaller and smaller components which can be absorbed and assimilated into the body

2. . The pharynx is an organ found in vertebrates and invertebrates, though the structure is not universally the same across the species. In humans the pharynx is part of the digestive system.

3. The liver is a vital organ of the digestive system present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemical necessary for digestion

4. The stomach is a muscular, hollow, dilated part of the digestion system which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects and molluscs. It is involved in the second phase of digestion, following mastication (chewing).