The rationale in this paper is that in order to make meaning of science in school, students are dependent on representations as mediating means. Besides that, learning concerns establishment of continuity between purposes, e.g. Johansson & Wickman (2011) suggested that learning progressions could be analysed from proximate purposes (close to students´ prior experiences) and ultimate purposes (more scientific ones). The aim is to investigate ways that secondary students, 14 years old, learn about the human body by focusing meaning-making of representations. The ultimate teaching purpose was articulated as “transportation and transformation of substances which will eventually reach the cells”. The research questions concern in what ways representations afford and hinder the students’ ways of making sense of the content The issue of exchange of substances came up early in the production of the representation because the students found it necessary to explain how material exchange across surfaces between organs was possible. The students decided that substances “jump” thus avoiding articulation of the specific mechanism and later the jump was visualized with arrows and text. The metaphor ‘jump’ offers an agreed term that ‘stands fast’ (Wickman, 2014) and allows students to move forward even though the material processes associated with jumping are not clear. It acts as a place holder metaphor that sequentially becomes more articulated and refined as students views of what is being exchanged, and where, are developed as part of the ultimate purposes of the sequence. The students started their conversations with naming the substances that enter the body using everyday terms like food and air however these words are replaced by nutrition/oxygen (intermediate wording) to nutrients/glucose and oxygen molecule. The gradual transformation of wording towards a more scientific language could be explained by the teacher´s re-phrasing when talking with students. Another reason might be that the affordance of visual diagrams lies in the way it productively constrains attention (Prain & Tytler, 2012) and thus creates a need for inclusion of other semiotic resources like arrows and formulas. The scientific language progression towards more discriminating and technical terms, as described above, is one of the key factors that scaffold the progression. Another factor is that the ambition of establishing continuity between proximate and ultimate purposes (Johansson & Wickman, 2011) seems to work for these activities. The students often ask each other “where does this substance go now?” or “how does it reach the cell?”.