Relationship between ki and physical body

Does a correlation between ki and physical body exists or the physical body is only a "tank" for ki?
I believe that it would be better if the ki system was based also on "physiological" and biological
factors.
For example Saiyans could be stronger because of their different muscle structure

Gohan explained it to Videl during her flying training. It's the latter. Everybody has ki, most humans just aren't skilled enough to utilize it.

Saiyans are just genetically much stronger than humans. The fact that they are race that thrive on battle and send their young children to conquer planets, as well as get stronger after recovering from injuries really helps.

Yeah everyone has Ki except RRA androids. It just takes skill to be able to gather, amplify and fire it.