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In the alveoli, oxygen from the air is absorbed into the blood. Carbon dioxide, a waste product of metabolism, travels from the blood to the alveoli, where it can be exhaled. Between the alveoli is a thin layer of cells called the interstitium, which contains blood vessels and cells that help support the alveoli.
A P-v diagram for liquid water. The compressed fluid region is located to the left of the blue line (the liquid-vapor phase boundary). A compressed fluid (also called a subcooled fluid or subcooled liquid) is a fluid under mechanical and or thermodynamic conditions that force it to be a liquid.