Any muscles attaching to the ribs can potentially move one rib relative to another and therefore act as accessory respiratory muscles. Muscles in the neck and the abdomen can fix or alter the positions of upper and lower ribs.
Two pleural cavities, one on either side of the mediastinum, surround the lungs (Fig. 3.37):
Superiorly, they extend above rib I into the root of the neck.
Inferiorly, they extend to a level just above the costal margin.