Why is the digestive system so important?
Because digestive system breakdown the complex macromolecules we eat into simpler substances i.e nutrients that can be absorbed by our body in order to get energy.
Digestive system constitutes the whole
Food we eat is the body's source of fuel. Before food can be used it has to be broken down into tiny little pieces. The predominant feature of digestive system is to grind the complex molecules of food e.g carbohydrates, proteins & lipids into the simpler one e.g monosaccharides, amino acids and fatty acids via mechanical and chemical digestion. These simpler substances are nutrients which are absorbed which then provide energy to body cells which they need to operate. Hence, if there would be no digestive system, there would no energy and no energy means no life.
Besides, digestive system has role in immunity which mean like immune system it also tries to keep the body free from foreign invaders. For example, lysozyme that is an enzyme present in saliva breaks down bacterial cells.
Hope it helps!