The graphic is called "Bagpipe anatomy"
The lungs or belly is the bag and can be made of leather, Gortex or other material. Some have a zip, others a drain for condensation but most do not.
Construction
Glossary for the experienced reader.
Compare the two uses of "bagpipe/s". The traditionalist refers to the instrument as bagpipe. If a plural is needed, it may be in a sentence such as "John will be playing the pipes tonight."