Digestion is the process of turning nutrients into less complex, soluble compounds that are easily absorbed into the blood and lymph. A variety of nutrients (proteins, fats, starch, etc.) contained in food and necessary for human life are insoluble in water. They can not penetrate into the blood and are absorbed by the body without prior treatment. In the digestive system, these nutrients are ground, crushed, and transferred into soluble compounds.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.