Uso de gestos-como recurso-mediador-por un profesor de bachillerato para enfrentar un desaf{\'i}o did{\'a}ctico no previsto por {\'e}l.

In this article, we report how a high school teacher (levels 10-12) used gestures when facing a classroom situation not foreseen by him. The use of gestures took place during the interaction with three students around the analysis of the movement of an object in free fall. A qualitative analysis of the data was carried out from a conceptual framework that coordinates elements of three theoretical approaches: documentational approach to didactics, activity theory and historical epistemology. The data collection was carried out by videotaping the teacher-student interaction while the meaning production process about the movement of an object in free fall took place. We consider that the analysis of results shows that the coordination of gestures is, on the one hand, a semiotic resource that should be considered relevant in the teachers' resources system; and on the other hand, represents in itself, a way of visualizing the cognitive structure that guides the actions of the teacher.