This is the 14749th most frequent Polish word.
płucach
"Płucach" means "lungs" (locative case) in English.
In this sentence, "płucach" is used to refer to the lungs as a physical organ, indicating where the air is contained.
Mam w płucach dużo powietrza po głębokim oddechu.
I have a lot of air in my lungs after a deep breath.
Here, "płucach" is used to describe the anatomical location where important respiratory tissue is situated.
W płucach znajduje się ważna tkanka do oddychania.
Important tissue for breathing is located in the lungs.
In this context, "płucach" is used to express the sensation of pain localized in the lungs after prolonged activity.