Understanding biological structures and functions is often difficult because of their complexity and micro-structure. For example, the vascular system is a complex and only partly visible system. Constructing models to better understand biological functions is seen as a suitable learning method. Models function as simplified versions of real objects and concentrate on special features of those to facilitate learning. Because of the complexity of the vascular system, models can be implemented as beneficial teaching aids. Learning with models is also an effective form in combination with collaborative learning. This paper introduces three simplified heart and blood vessel models. They were designed for collaborative learning. The models were implemented in a study with 7th grade students (13 years old). Results of a paper-pencil evaluation show that collaboratively learning with models of the heart and the blood vessels was interesting for students. Furthermore, students gained better understanding and achieved higher test scores. (Contains 9 figures and 1 table.)