There are three types of joint mentioned here Diarthrosis: it refers to the moving joints of the body, that is the synovial joints. These are more numerous in the members. In a synovial joint, the bones are associated through a cavity filled with a liquid called "synovium".
Amphiarthrosic joints: Articulation uniting two bone surfaces covered with cartilage, to which it allows only limited movements. Like symphysis of the vertebral column and syndesmosis of the ankle.
Synarthrosis: Term for a motionless joint where contact between bones occurs through a fibrous structure. Like Synostosis (Cranium), Suture (skull), Gomphosia (mouth), Synchondrosis (cartilage).
True, air pollution is like smog in a city. It surrounds the atmosphere and causes you to breath in chemicals, the crops and plants that absorb the air as well. It's very harmful for your system and for the wildlife around.
