Lungs contain internal respiratory surfaces shaped as a cavity or sac. Lungs provide a membrane for gaseous exchange with blood. Gases diffuse across the inner respiratory surfaces of the lungs. Pulmonary circulation enhances the diffusion of dissolved gases into and out of lung capillaries. Human Respiratory System A. Airways to the Lungs 1.
Blood vessels warm the air and mucus moistens it.
Alveoli provide a tremendous surface area for gaseous exchange with the blood located in the dense capillary network surrounding each alveolar sac. How Breathing Changes Air Pressure in the Lungs 1. To inhale, the diaphragm contracts and flattens, muscles lift the rib cage upward and outward, the chest cavity volume increases, internal pressure decreases, air rushes in. The nervous system controls oxygen and carbon dioxide levels for the entire body. Respiration in Unusual Environments A. Decompression Sickness 1.