Anatomy, Thorax, Wall Movements

Pulmonary ventilation, more commonly referred to as breathing, is the movement of air into and out of the lungs. Inhalation is the act of drawing air into the lungs, while exhalation is the expulsion of that air out of the lungs. Breathing involves Boyle’s law, which states that the pressure of a gas decreases as the volume increases if the temperature is held constant. Increasing the volume of the thoracic cavity causes a decrease in the intrathoracic pressure and an influx of air. Meanwhile, decreasing the volume of the thoracic cavity generally occurs by the relaxation of the muscles of inspiration, which causes an increase in intrathoracic pressure and results in exhalation. The thoracic wall is essential to this process and is made up of the sternum, 12 pairs of ribs, 12 thoracic vertebrae, and the muscles, fascia, and skin that connect to this bony cage.