@anamur-- You're right. People always talk about collagen in the skin, which makes us forget that there is collagen everywhere, in all of our organs and tissues. Because without collagen, we wouldn't be able to keep our organs and tissues together. Along with collagen and several other proteins, our body can function without falling apart. Collagen helps keep everything together, intact and flexible. It's super important.
I learned about collagen types I, II and III from my sister who is a nurse. But I wish I had learned about it before, in science and biology courses at school.