* ASTDN: Association of State and Territorial Directors of Nursing
Description of the *ASTDN Model
This model consists of three concentric circles. The center circle depicts the nursing process or the art and science of nursing practice. The middle circle suggests a flow or movement of the core functions of assessment, policy development and assurance. The 10 essential services of public health are detailed in the outer circle. The model demonstrates the dynamic nature of the practice of public health nursing within the framework of the core functions and the essential services. The activities performed to accomplish the public health core functions and essential services will include all of the elements of the nursing process. For example, a nurse may utilize evaluation (an element of the nursing process) for policy development (a core function) in monitoring health status to identify community health problems (an essential service).