Ventilation

Contraction of intercostals muscles allows ventilation of the lungs to take place in mammals. This introduces o2 to the gas exchange surface, the epithelium of the alveoli of the lungs. In order to maintain a high conc grad, the o2 is rapidly removed, a process involving another mineral ion, iron. Iron ions are attached to haem groups on haemoglobin inside red blood cells. The iron can form bonds to o2, allowing haemoglobin to load o2 in the lungs when the pp0 is high. Each molecule of haemoglobin can bind 4 O2 mols allowing a rapid saturation and the production of oxyhaemoglobin. On contraction of the ventricles, the pressure forces the red blood cells through the body to regions where pp0 is lower. Here, the haemoglobin unloads, making o2 available for aerobic respiration and the production of ATP.