Just as in any military structure, the medical needs are assigned to one department. They need someone to give medical attention to the troops. This falls upon the CMO: Chief Medical Officer.
The CMO is in charge of all aspects of medical treatment using a variety of methods. Everything from soldiers trained as medics, to other doctors, to high tech methods such as the medical droids. In short, if someone is hurt and/or dying it is the responsibility of the CMO to see to their needs.