I'll be leading our First Grade Co-op lessons...starting mid-month, or for April (I was supposed to lead March, but following the death of my aunt I had to ask my fellow members to step in for a couple weeks,) we'll be doing a study of body systems.
I'll be starting with respiratory system, and found this:
Respiratory System: TeachersPayTeachers
Also: Nervous System, Skeletal System, Components of blood, Digestive System
And: Smart Art Body Systems this one is $3.00 but when you are using in a small group like this, it's not a big cost.