State the role of the C-shaped cartilage rings in the human trachea and explain why these rings are incomplete at the posterior surface adjacent to the oesophagus.
Describe three distinct structural adaptations of the human alveoli and explain how each feature maximises the rate of gas diffusion into pulmonary blood capillaries.
State the approximate percentage of carbon dioxide found in inspired atmospheric air and in expired air.
State one physical difference other than gas composition between inspired air and expired air, and explain its physiological cause.
A student uses the apparatus shown in the diagram to compare the carbon dioxide content of inspired and expired air by breathing in and out through the central mouthpiece for 30 seconds. Describe the expected observation in Flask A and Flask B, and explain the biological reason for the difference in results.