Fig. 1.1 is an image of a transverse section through the trachea of the gas exchange system. [Figure 1.1]

1. (a)Write the names of structures X and Y on Fig. 1.1 in the boxes provided.[2]
2. (b)The perichondrium contains collagen fibres, composed of collagen molecules. Collagen is an example of one type of biological molecule. State the name of the type of biological molecule of which collagen is an example.[1]
3. (c)Some structures in the gas exchange system are listed in alphabetical order in Table 1.1. Write YES in the box provided if the structure contains smooth muscle. Write NO in the box provided if the structure does not contain smooth muscle. [Table 1.1][1]

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