Practise IB Biology SL 3.1.5 using exact SL questions tracing diaphragm and intercostal action through thoracic pressure, volume and airflow.
Explain the need for a ventilation system and the mechanism of ventilation of the lungs in humans
a. (cellular) respiration drives the need for gas exchange/absorption of oxygen and removal of CO2;
b. gas exchange depends upon a ventilation system;
c. lungs/alveoli provide surface area for gas exchange (with capillaries/blood);
d. ventilation system maintains a high concentration of oxygen in the alveoli;
e. bloodstream links alveoli to cells;
f. inhalation by contraction of diaphragm;
g. inhalation occurs with contraction of external intercostals/relaxation of internal intercostals;
h. (these) increase the volume/reduce the pressure in thorax, pulling air into lungs;
i. exhalation caused by relaxation of the diaphragm; j. exhalation occurs with relaxation of external intercostals/contraction of internal intercostals;
k. (these) decrease volume/increase pressure in the thorax, forcing air out of lungs;