Simplify the following text for a Grade 6 native English-speaking person.
Original: The ileum ( Ë É lÉ É m ) is the final section of the small intestine in most higher vertebrates , including mammals , reptiles , and birds . In fish , the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine may be used instead of ileum .
Simplified: The ileum is the last section of the small intestine .