Design Control is a set of management practices such as procedures, processes and policies. They have to be followed to ensure proper quality and to correct any errors during the product development. Medical devices must meet quality and safety standards. Otherwise these products might be called for recall due to design problems. The recall can be very costly for the manufacturer. In the order to make sure that the medical device is done correctly manufacturers develop proper documentation to confirm that the design criteria are met.
The Design and development plan is written to plan the design activities. It forms the roles to all the departments so the product meet the right criteria.

Thanks