Structure:
The skeletal muscles of the chest
and neck, pulling on the ribs, and the diaphragm are parts of the body
that permits breathing. The lungs are the organs inside the chest where
respiratory gasses such as oxygen and carbon dioxide are exchanged. In
amphibians, respiration also occurs, in part,
through the thin, moist skin,
but some species of salamanders have only gills and either no, or small
lungs.
Function:
As the chest expands and contracts, gasses move through the windpipe, called
the trachea; oxygen comes in, and carbon dioxide is expelled. The exchange
occurs in thin, alveolar sacs, because the chemical attraction of oxygen
for the hemoglobin pigment of red blood cells is greater than its attraction
for carbon dioxide. These cells wear out in about 120 days, and are continually
replaced by hematopoiesis.
