Civil engineering covers a broader spectrum. Civil engineering students study Structural engineering, water engineering, Geotechnical engineering (soil mechanics) and Traffic and Transport...
I'm not sure why this question is in cardiovascular health and I'm not a medical doctor. I will assume this question was placed in the wrong category and you are asking about he field of engineering....
Structural engineering is usually limited to the design of buildings and other structures. Mechanical engineering includes the same type of components but usually as part of a piece of equipment....