Requirements for Design Controls
1. Design planning
2. Design input and output
3. Design verification and validation
4. Design review
5. Design changes
6. Design transfer
7. Design history file

Design Control is in place so that all documents are in place and everything can be back traced is place of problem.
Reviews are in place to on every steps those are:- user needs, device input, device process, device output,Medical Device.
Verification are done at device input and device output.
Validation is done at medical device and user needs just to verify if the device is working as its intended to work and if it really fulfills the purpose which it was made for.