IB Biology SL - Gas Exchange

6.4 Gas Exchange

6.4.1 Distinguish between ventilation, gas exchange and cell respiration

Ventilation: muscle movement to move fresh air into alveoli
Gas exchange: replacing carbon dioxide with oxygen in blood in lungs

Cell respiration: cellular energy production from glucose

6.4.2 Explain the need for a ventilation system

most cellular respiration is aerobic/requires oxygen / produces carbon dioxide;

they have thin walls with less elastic tissue/muscle/wider lumen;

ventilation system exchanges gases between inhaled air and lungs/blood stream;

ventilation system maintains high concentration gradient of gases in alveoli/ lungs

6.4.3 Describe the features of alveoli that adapt them to gas exchange.

Large total surface area à efficient gas exchange

Wall of single layer of flattened cells à short diffusion distance allowing rapid gas exchange

Moist lining à for the gases to diffuse into the blood before absorbed and to prevent the walls of the alveoli from sticking together

Walls elastic à

Network of capillaries à Have a low oxygen and high carbon dioxide concentration, allowing oxygen to diffuse into the blood and carbon dioxide to diffuse out of the blood

Capillary walls are thin/one cell thick

6.4.4 Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles and alveoli.

                         

6.4.5 Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles.

external intercostal muscles contract;

internal intercostal muscles relax;

pulling the rib cage upwards;

diaphragm contracts and flattens;

increase in volume of thoracic cavity;

this reduces pressure;

so air enters the lungs;