As part of a series of investigations in which we explore the integration of verbal and nonverbal aspects of communication into a dialectical, sense-constitutive unit during science lectures, this study adapts the notions of catchments (i.e., repetitions of essential features of the gesture-speech dialectic) and growth points (i.e., moments in which ideas in the form of a gesture-speech dialectic are born) to analyze, from a multimodal communicative perspective, the articulation and development of scientific concepts in the course of several consecutive lessons dealing with the circulatory system. The presence of catchments and the identification of growth points "within" and "across" lessons allow us to understand how scientific concepts are instantiated (i.e., taught) in and during science lectures. The results of our analysis make evident the dialectical relations between the various semiotic resources that are integrated into the communicative unit, helping us elucidate teaching of scientific concepts as a process, a drama in several acts, that unfolds in time and across consecutive lectures.