Breathing and Exchange of Gases

Lungs are made up of air-filled sacs, the alveoli. They do not collapse even after forceful expiration, because of

1. inspiratory reserve volume
2. tidal volume
3. expiratory reserve volume
4. residual volume.

Reduction in pH of blood will

1. decrease the affinity of haemoglobin with oxygen
2. release bicarbonate ions by the liver
3. reduce the rate of heart beat
4. reduce the blood supply to the brain.

Name the chronic respiratory disorder caused mainly by cigarette smoking.

1. Respiratory acidosis
2. Respiratory alkalosis
3. Emphysema
4. Asthma

Asthma may be attributed to

1. inflammation of the trachea
2. accumulation of fluid in the lungs
3. bacterial infection of the lungs
4. allergic reaction of the mast cells in the lungs.

The partial pressure of oxygen in the alveoli of the lungs is

1. equal to that in the blood
2. more than that in the blood
3. less than that in the blood
4. less than that of carbon dioxide.

Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because

1. there is a negative pressure in the lungs
2. there is a negative intrapleural pressure pulling at the lung walls
3. there is a positive intrapleural pressure
4. pressure in the lungs is higher than the atmospheric pressure.

Name the pulmonary disease in which alveolar surface area involved in gas exchange is drastically reduced due to damage in the alveolar walls.

1. Pneumonia
2. Asthma
3. Pleurisy
4. Emphysema

When you hold your breath, which of the following gas changes in blood would first lead to the urge to breathe?

1. Falling CO2 concentration
2. Rising CO2 and falling O2 concentration
3. Falling O2 concentration
4. Rising CO2 concentration

Approximately seventy percent of carbon dioxide absorbed by the blood will be transported to the lungs

1. as bicarbonate ions
2. in the form of dissolved gas molecules
3. by binding to R.B.C.
4. as carbamino-haemoglobin.

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. [Figure]

1. A - Trachea - Long tube supported by complete cartilaginous rings for conducting inspired air.
2. C - Alveoli - Thin walled vascular bag like structures for exchange of gases.
3. B - Pleural membrane - Surround ribs on both sides to provide cushion against rubbing.
4. D - Lower end of lungs - Diaphragm pulls it down during inspiration.