Describe the mechanism of gaseous exchange in a mammal

K.C.S.E Biology Q & A - MODEL 2008PP2QN08

Describe the mechanism of gaseous exchange in a mammal

answers

Breathing in
External intercostals muscles contract; internal, intercostals muscles relax lifting/ raising the ribcage upwards and outwards; muscles of diaphragm contract. It flattens the volume of the thoracic cavity increases; pressure decrease; higher air pressure in the atmosphere forces air into the lungs
  Breathing out
External intercostals/ muscles relax; internal intercostals muscles contract moving the ribcage downwards and inwards; the muscles of diaphragm relax, the diaphragm assumes dome shape; volume of thoracic cavity decreases; while pressure increases; higher pressure forces air out of the lungs