Best path-finding algorithm with minimum changes of direction

arithmetica

Hi everyone,
I'm trying to design an algorithm finding the shortest path between two nodes in a simple graph such that this path has the minimum number of changes of directions. So, the path would be the shortest and straightest of all. For the shortest part, I would apply a Dijkstra algorithm but I don't know how to modify it to match the straightest part.
Any help would be appreciated.