(in french)The problem of modelling a mechanical biological system is studied in this thesis through the modelling and simulation of the trunk movements during respiration. The aim is the realistic graphical representation of these movements. The organisation of the present document suggests methodological steps for modelling.In the first part, the mechanical principles of the respiratory phenomena are explained. Then, the problem appears as the modelling and behavioural simulation under constraints of a complex object composed of regions having different properties (elasticity, motor functioning and rigidity). Physically-based dynamic methods are suited to our aim. A state of the art of these methods and their problematic is drawn up.The second part presents the making of the computer model by specific property regions. The geometric and dynamic based are proposed, the notion of force generated by an attractive point is defined. A new elastic function that uses this notion and the expression of local shape memory is presented. This function is then successfully compared to another elastic function. The modelling of muscle and solid regions is then explained. How to constrain the model is then study. We develop a new direct resolution method that allows verifying local and global constraints without any need for iterative algorithms. The incompressibility constraint resolution illustrates this resolution method, its principles are generalised to be used independently of our model.The last part of this thesis gives a qualitative validation of our model by the use of some examples, including the simulation of trunk movements during respiration.