Aspects of human physiology assignment?

I am doing an assignment currently.
The main things to consider is activities undertaken in a typical day such as eating, drinking, physical work and exercise. I have to describe the structure and function of the relevant organ systems which allow the body to carry out these activities in a controlled and coordinated way. I have written around 8000 words with the appendix. I am struggling with the structure though.

How have you structured it so far? What level are you studying at? 8000 words seems like quite a lot , although the assignment is quite broad and there is a lot of detail to go into.

It's A level Human Physiology. The word limit is 3500 but you can go over in the appendix

What is included in your appendix? An additional 4500 words in the appendix when the assignment is 3500 sounds like a lot. You shouldn't use the appendix to bypass the word limit, I'm not saying that's what you've done.