Contextual features of assessments can influence the ideas students draw from and the ways they assemble knowledge. We used a mixed-methods approach to explore how surface-level item context impacts student reasoning. In study 1, we developed an isomorphic survey to capture student reasoning about fluid dynamics, a crosscutting phenomenon, in two item contexts (blood vessels, water pipes), and administered the survey to students in two different course contexts: human anatomy and physiology (HA&P) and physics. We observed a significant difference in two of 16 between-context comparisons and a significant difference in how HA&P students responded to our survey compared with physics students. In study 2, we conducted interviews with HA&P students to explore our findings from study 1. Using the resources and framing theoretical framework, we found that HA&P students responding to the blood vessel protocol used teleological cognitive resources more frequently compared with HA&P students responding to the water pipes version. Further, students reasoning about water pipes spontaneously introduced HA&P content. Our findings support a dynamic model of cognition and align with previous work suggesting item context impacts student reasoning. These results also underscore a need for instructors to recognize the impact of context on student reasoning about crosscutting phenomena.