The group of similar cells working together to perform a specific job is called a tissue. The functional group of multiple tissues is called organ. Functionally related organs form organ systems, which all together form one organism.
So, surgeon is working at the organ level. The lungs are the organs of transpiration. Since they are organs, they consist of multiple tissues, which consist of many cells. But the surgeon does not work on one single cell, he works with the whole organ.
