Writing the introduction of an explanation text about the digestive system

An introduction's purpose is to give general facts about the topic and to tell the reader what they will learn. Digestion is the process of breaking down food into particles small enough to be absorbed into the bloodstream. The scientific definition of digestion, and the use of scientific vocabulary, are essential for introducing the subject. The relative pronoun "which" can be used to embed a relative clause within a main clause to add detail. A relative complex sentence is formed of a main clause and a relative subordinate clause.