What happens after application in..?

[Durban]

Hi. We have lodged our study permit with our embassy in South africa and am waiting for confirmation. Do you know if they keep your passports and all the docs while we go for medicals. I understand they send you a letter of introduction (which then gets presented at immigration in canada) and your forms to do medical. How does the medical fit in (processing of medical is another 4 weeks). I just cant seem to find exact detail on the finer details of next step?
thanks