The respiratory system
The following structures can be found in the human thorax:
- bronchi (left and right bronchus)
- intercostal muscles
- pleural membranes
The trachea branches into two bronchi (one to each lung). Pleural membranes surround each lung. Cartilage rings in the walls of the trachea help to keep it open.
The bronchi split into smaller and smaller tubes called bronchioles. These end in microscopic air sacs called alveoli. There is a muscular diaphragm below the lungs.