Ronnie fell off her bike and scraped her knee pretty badly. Alexa and Penny watched with fascination as I cleaned Ronnie up and applied bandages.
When it was time to change the dressing, Alexa asked if she could do it. After the girls looked at the section in our first aid book on how to care for wounds, and after we practiced on a baby doll, I supervised Alexa in helping Ronnie change her bandages. 
Penny loved the First Aid book, or as she called it, The Blood Book, and kept asking questions about all the pictures. I taught her what different wounds are called and how they might happen. Ronnie and Alexa started listening too, so we had a nice little story time about abrasions, lacerations, stabs, contusions, punctures, and gunshot wounds.
To take the impromptu lesson further, I had an idea to three-dimensionally represent the creation of a wound. I left a nice imprint of my skin behind as I flattened some clay and used different tools to create "wounds" on the clay. Aftwerward, I gave Ronnie and Alexa a fun little quiz.
Penny opted out of quiz time and just spent the rest of the afternoon wounding clay.
