EMS does not exist in isolation, but is integrated with other services and systems intended to maintain and enhance the community's health and safety. As seen in the graphic below, EMS operates at the crossroads between health care, public health and public safety. A combination of the principles and resources of each is employed in EMS systems. Since EMS providers work in the community, they are often the first to identify public health problems and issues. The emergence of significant health problems is often heralded by its arrival in the Emergency Department – and it arrives via EMS. Since EMS providers respond to all kinds of emergencies and all kinds of hazards, they often work shoulder-to-shoulder with public safety colleagues in law enforcement and fire services. But their primary mission is emergency medical care.

The organizational structure of EMS, as well as who provides and finances the services, varies significantly from community to community. Prehospital services can be based in a fire department, a hospital, an independent government agency (i.e., public health agency), a non-profit corporation (e.g., Rescue Squad) – or be provided for by commercial for-profit companies. But, regardless of provider, the essential components of an EMS System remain the same.

The diagram right illustrates the complexity of an EMS system. In the diagram, the large circle represents each system element as it is activated in response to an incident. The "brown arrowed" elements within the circle represent the specialty care areas within EMS. The list within the circle represents the elements acting "behind the scenes" to support the system. In order to be "ready every day for every kind of emergency," an EMS system must be as comprehensive as the one pictured above. Developing and maintaining such a system requires thoughtful planning, preparation, and dedication from EMS stakeholders at the local, State, and Federal levels.