In SMESH you can easily construct groups of specific elements (nodes, edges or faces) which will be taken from a definite submesh.
To construct a group of specific elements:
Right-click on a submesh in the Object Browser and choose the Construct Group item or select your submesh in the Object Browser and in the Mesh menu chose the Construct Group item. SMESH will construct several groups consisting of elements of the definite type: nodes, edges or faces