Periosteum is a membrane that covers the outer surface of all bones, except at the joints of long bones. Endosteum lines the inner surface of all bones.
The process of breathing involves the exchange of gases, namely, oxygen and carbon dioxide that occurs between you, in particular, the cells of your body, and the outside environment, which is the air. This exchange happens in the lungs. In all, breathing has two components: Ventilation, or movement of oxygen into, and carbon dioxide, out of your lungs. Circulation, or transporting the oxygen taken into the body during ventilation to where it is needed in the body. In terms of how breathing can enhance your therapeutic back exercise program or your successful participation in a pro-active holistic therapy, it's the ventilation component that takes center stage.
As the space in the chest cavity gets smaller, air rich in carbon dioxide is forced out of your lungs and windpipe, and then out of your nose or mouth. Breathing out requires no effort from your body unless you have a lung disease or are doing physical activity.