(a(i))[2]
Name the cells marked A and B in Fig. 4.1.
(a(ii))[3]
Describe how the tissue shown in Fig. 4.1 is adapted for its role in the gas exchange system.
(b(i))[2]
The structures labelled X in Fig. 4.1 have a distinctive internal structure, as shown in Fig. 4.2. Describe the internal structure of the structures labelled X.
(b(ii))[1]
Explain how Fig. 4.2 shows that each of the structures labelled X is intracellular.
(c)[4]
Stem cells are present in the lining of the bronchi. Describe the function of centrioles and explain how they take part in the cell cycle of a stem cell.