Passage involves crossing single layer of squamous epithelium surrounded by blood capillaries. Film of lipoprotein lines inner alveolar surfaces to lower surface tension and prevent them from closing up. Mechanism of Breathing Respiration refers to complete process of supplying oxygen to body cells and ridding body of carbon dioxide. Getting Air to the Lungs a. Vital capacity is maximum volume of air that can be moved in and out during a single breath.
Vital capacity is sum of tidal, inspiratory reserve and expiratory reserve volumes.
In emphysema , residual volume builds up and is no longer useful for gas exchange, reducing vital capacity. Inspiration Precedes Expiration a. Air passes from atmosphere through pharynx to alveoli. Lungs lie within a sealed-off thoracic cavity. The intrapleural pressure is less than atmospheric pressure by about 4 mm Hg. Due to greater atmospheric pressure outside, air rushes in.