Final answer:
In the context of biology, the diaphragm is a muscle that deforms during breathing by contracting and relaxing. A 'rigid diaphragm' in biological terms does not apply as the biological diaphragm is inherently flexible and designed for movement.
Step-by-step explanation:
In a rigid diaphragm, neither the diaphragm nor the walls deform because a rigid diaphragm is a term that typically refers to a structural component in engineering rather than biology. In the context of biology, the diaphragm is a domed-shaped muscular partition separating the thoracic cavity from the abdominal cavity and is not rigid. It contracts and relaxes to aid in breathing. The diaphragm itself is the structure that deforms during the process of breathing, allowing the thoracic cavity to change volume and the lungs to fill with air.
In physiology, deformation would typically refer to the changes in shape that organs or muscles undergo during their function. For instance, muscles contract and relax which can be viewed as a form of deformation. However, this is different from engineering or physics where a rigid diaphragm might be considered a static structure designed not to deform.