Biology 9700 · AS & A Level · The gas exchange system

The gas exchange system — practice question

The Weibel Lung model was created from a thorough investigation of the gas exchange system. It records precise airway diameter measurements, namely the lumen diameters of the airways. Within the model, the different regions of the gas exchange system are assigned a generation number, as shown in Fig. 6.1.
(a)[1]

In the Weibel Lung model, each airway splits into two branches. Name the airways in generation 1, labelled X in Fig. 6.1, that come from generation 0.

(b)[2]

The airways receive a good blood supply. However, the airways from generation 0 to generation 16, shown in Fig. 6.1, cannot perform gas exchange. Suggest why the airways from generation 0 to generation 16 are not able to carry out gas exchange.

(c)

High-resolution computed tomography (HRCT) is an imaging method used to measure airway diameters in people with a pulmonary (lung) disease. It must not be carried out repeatedly at regular intervals because it exposes patients to harmful radiation. Researchers investigated another method, HP gas MRI, which does not involve harmful radiation. Two MRI image types, called projection and multi-slice, were used to measure airway diameters. Fig. 6.2 presents the HP gas MRI results compared with the Weibel Lung model for generations 0 to 5. The Weibel Lung model served as the reference standard for airway diameters.

(c(i))[1]

State the relationship shown in Fig. 6.2 between airway diameter and airway generation for the Weibel Lung model data.

(c(ii))[3]

Using the data in Fig. 6.2, explain whether HP gas MRI could be a useful substitute for HRCT when measuring airway diameters.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: Left and right bronchus (bronchi)

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI