Explore how diaphragm and intercostal muscles change thoracic volume and pressure to drive inspiration, expiration and exercise ventilation in IB Biology HL B3.1.5.
Explain the mechanism of ventilation of human lungs.
ventilation is movement of air into and out of lungs;
volume of thorax/lungs/chest increased/decreased;
pressure in thorax/lungs/chest decreased/increased;
air flows from higher to lower pressure / air flows until the pressures are equal;
During inspiration/inhalation:
external intercostal muscles contract so ribcage moved up/out;
diaphragm contracts so moves down/becomes flatter;
internal intercostal/abdomen (wall) muscles relax;
During expiration/exhalation:
external intercostal muscles relax so ribcage moved down/in;
diaphragm relaxes;
recoil of elastic fibres that stretched during inspiration;
internal intercostal muscles contract (during forced ventilation);
abdomen (wall) muscles contract (during forced ventilation);