Consensus was reached on seven core concepts of physiology using the Delphi method, including 'Integration' outlined by the descriptor, 'Cells, tissues, organs, and organ systems interact to create and sustain life' This Core Concept was unpacked by a team of three Australian physiology educators into hierarchical levels, identifying five themes and ten sub-themes, up to one level deep. The unpacked core concept was then circulated amongst twenty-five experienced physiology educators for comments and to rate both level of importance and level of difficulty for each theme and sub-theme. Data were analysed using a one-way ANOVA to compare between and within themes. The main theme 'The body is organised within a hierarchy of structures, from atoms to molecules, cells, tissues, organs, and organ systems' almost universally rated as 'Essential' Interestingly, the main theme, also rated between 'Slightly Difficult' to 'Not Difficult', which was significantly different from all other sub-themes. There were two separate subsets of themes in relation to importance, with three themes rating between 'Essential' and 'Important', and the two other themes rating as 'Important'. Two subsets in difficulty of the main themes were also identified. While many core concepts can be taught concurrently, Integration requires application of prior knowledge, with expectation that learners should be able to apply concepts from cell-cell communication, homeostasis and structure and function, prior to understanding the overall Integration core concept. As such, themes from the Integration core concept should be taught within the endmost semesters of a Physiology program.