Thorax vs Pleuretic - What's the difference?

As a noun thorax

is thorax (region of the mammalian body).

(anatomy) of or pertaining to the pleura, the smooth serous membrane which closely covers the lungs and the adjacent surfaces of the thorax.

(en-noun)

the middle of three distinct divisions in an insect, crustacean or arachnid body

the region of the mammalian body between the neck and abdomen as well as the cavity containing the heart and lungs

* thoracic * thoracal * thoracic vertebra * thoracoplasty

(-)

(anatomy) Of or pertaining to the pleura, the smooth serous membrane which closely covers the lungs and the adjacent surfaces of the thorax.

which I expected to have found extremely sizy and glutinous, or indeed coagulated, as it is in pleuretic complaints;