O Level Biology Mechanisms of ventilation in the Human lungs

O Level Biology Mechanisms of ventilation in the Human lungs

This is the  method  that  pumps air into  and  out   of the lungs  of  mammals it occurs  in two  faces

• Breathing In ( Inspiration or  Inhalation )
• Breathing Out  ( Expiration  or  exhalation )

Mechanisms  of  Breathing  In  (Inspiration )

The  external  intercostal  muscles  contract while  the  internal  intercostal  muscles  relax . this cause  the  rip  cage  upward and outward .At  the same time  the  dome  shaped diaphragm  muscles  contracts pulling  it downward to  assume a  flat  shape . This  action  results in an  increase in the volume  of  the  thorax and a  decrease in the pressure  alone the lungs  such  that  the pressure  falls   below  external  air  pressure  . These cause  air to   fall  in the  lungs

Mechanisms  of  Breathing  out   (Expiration)

The  external  muscles  relax  while the intercostal muscles contracts  this causes  the rid cage to  move downward and inward .At  the same time the flatten diaphragm muscles  relax  allowing  the  liver  below it  to  push it backward   to  it  original  resting  dome shaped . This  action resolve  in the decrease  of the thorax and increase in the pressure around the  lungs  such as  that   pressure  around  the lungs  rises  above external  air pressure  .This cause  air  to  be forced  out of the  lungs  .

Difference between inspiration and expiration