I heard that rib besides protecting our lungs, promoting the breathing action, it also produce red blood cells. Is it true?

The ribs are bones, they don't make red blood cells as far as I am aware.

bone marrow DOES make red blood cells.

 

take a peek here: http://www.cancerhelp.org.uk/help/default.asp?page=314

yeah, any bone with marrowbone in it contributes to the production of red and white blood cells

 

as for breathing, the muscles and cartelage inbetween the ribs contract, causing the rib cage to shrink and expel air from the lungs (blow out quickly and pay attention to your ribs)

Intercostal and Diacostal muscles are the ones used to make them move IIRC form old singing lessons.

What seperate the thoracic wall and the pleural membrane?

Nothing, IIRC... i believe the pleural membrane is a double-layer of membrane which seperates the lungs from the ribs. theres probably some fluidy stuff inbitwix.

Fluid in the thoracic wall? Isn't the wall comprise the outer membrane?

You mammals and your diaphragms and divided body cavities....

Pleura has two "folds", visceralis (also called pulmonalis) and parietalis (the outer one), with fluid in between that assists in respiratory action we call breathing. Pleura covers only the latera, dorsal and ventral (side, back and belly) side, but not the side where lung and mediastinum meet.