A large proportion of oxygen is left unsused in the human blood even after its uptake by the body tissues. This ${\mathrm{O}}_2$
1. raises the ${\mathrm{P}}_{{\mathrm{CO}}_2}$ of blood to 75 mm of Hg
2. is enough to keep oxyhaemoglobin
3. helps in releasing more ${\mathrm{O}}_2$ to the epithelial tissues
4. acts as a reserve during muscular exercise

What is true about RBCs in humans?

Which two of the following changes (1-4) usually tend to occur in the plain dwellers when they move to high altitudes (3,500 m or more)?

(a) Increase in red blood cell size
(b) Increase in red blood cell production
(c) Increased breathing rate
(d) Increase in thrombocyte count 

1. (b) and (c)
2. (c) and (d)
3. (a) and (d)
4. (a) and (b)

What is vital capacity of our lungs?
1. Inspiratory reserve volume plus tidal volume
2. Total lung capacity minus expiratory reserve volume
3. Inspiratory reserve volume plus expiratory reserve volume
4. Total lung capacity minus residual volume

The haemoglobin of a human foetus
1. has a lower affinity for oxygen than that of the adult
2. has the same affinity for oxygen as that of an adult
3. has only 2 protein subunits instead of 4
4. has a higher affinity for oxygen than that of an adult

People living at sea level have around 5 million RBC per cubic millimeter of their blood whereas those living at an altitude of 5400 metres have around 8 million. This is because at high altitude:
1. people get pollution-free air to breathe and more oxygen is available
2. atmospheric O₂ level is less and hence more RBCs are needed to absorb the required amount of O₂ to survive
3. there is more UV radiation which enhances RBC production
4. people eat more nutritive food, therefore more RBCs are formed

The majority of carbon dioxide produced by our body cells is transported to the lungs:
1. dissolved in the blood
2. as bicarbonates
3. as carbonates
4. attached to haemoglobin

Consider the following statements:

Which of the above statements are true?

Name the pulmonary disease in which alveolar surface area involved in gas exchange is drastically reduced due to damage in the alveolar walls.
1. Pleurisy
2. Pneumonia
3. Emphysema
4. Asthma

The figure shows a diagrammatic view of human respiratory system with labels A, B, C and D. Select the option, which gives correct identification and main function and/or characteristic.