CBSE Class 10 Science 2023 · Paper 31/5/2 · Question 24

(a) Rings of cartilage: they ensure that the air passage (the throat or windpipe) does not collapse, so air can pass freely to and from the lungs. (b) Alveoli: they provide a very large, thin surface, richly supplied with blood vessels, where the exchange of gases takes place; oxygen passes into the blood and carbon dioxide passes out of it. (c) Haemoglobin: this respiratory pigment of the red blood corpuscles has a very high affinity for oxygen; it takes up oxygen in the lungs and carries it to the tissues. (d) Lining of mucus: it traps dust particles and germs from the air breathed in, and so helps to filter the air before it reaches the lungs.