The diagram shows the structural and functional unit of the lungs.

(a) Identify structure Z.
Answer: Structure Z is the alveolus.

(b) Name the gases X and Y.
X: Oxygen (Oâ‚‚)

Y: Carbon dioxide (COâ‚‚)

(c) What is the name of the blood leaving at point E?
The blood leaving at point E is oxygenated blood.