NEET Biology Breathing and Exchange of Gases MCQs Set 10

Answer: (d) Pharynx

Explanation:
1. The pharynx is the common passage for food and air.

Teacher's Note:
1. Inspiration is caused by contraction of the diaphragm and external intercostal muscles, which enlarge the thoracic volume; expiration is normally passive.
2. Know the lung volumes: TV 500 mL, IRV 2500-3000 mL, ERV 1000-1100 mL, RV 1100-1200 mL.

Answer: (b) Incomplete cartilaginous rings

Explanation:
1. Trachea, primary, secondary and tertiary bronchi and initial bronchioles are supported by incomplete cartilaginous rings.

Teacher's Note:
1. Oxygen is carried mostly as oxyhaemoglobin (97 per cent) and CO2 mostly as bicarbonate (about 70 per cent).
2. Diffusion of gases depends on partial pressure gradient, solubility and thickness of the diffusion membrane.

Answer: (b) By the contraction in diaphragm, volume of thoracic cavity increases antero-posterior axis.

Explanation:
1. Contraction of the diaphragm flattens it and increases the volume of the thoracic chamber in the antero-posterior axis; the external intercostal muscles increase it in the dorso-ventral axis.

Teacher's Note:
1. Each 100 mL of oxygenated blood normally delivers about 5 mL of oxygen to the tissues.
2. pO2 falls from 104 mm Hg in alveoli to 40 mm Hg in deoxygenated blood, while pCO2 rises from 40 to 45 mm Hg.

Answer: (c) C and D

Explanation:
1. Forced expiration is helped by the internal intercostal muscles and the abdominal muscles.

Teacher's Note:
1. Inspiration is caused by contraction of the diaphragm and external intercostal muscles, which enlarge the thoracic volume; expiration is normally passive.
2. Know the lung volumes: TV 500 mL, IRV 2500-3000 mL, ERV 1000-1100 mL, RV 1100-1200 mL.

Answer: (a) Diaphragm and EICM

Explanation:
1. The diaphragm and external intercostal muscles increase the thoracic volume during inspiration.

Teacher's Note:
1. Oxygen is carried mostly as oxyhaemoglobin (97 per cent) and CO2 mostly as bicarbonate (about 70 per cent).
2. Diffusion of gases depends on partial pressure gradient, solubility and thickness of the diffusion membrane.

Answer: (a) i - c, ii - b, iii - d, iv - a

Explanation:
1. IRV is about 2500-3000 mL, ERV 1000-1100 mL, tidal volume 500 mL and residual volume 1100-1200 mL.

Teacher's Note:
1. Each 100 mL of oxygenated blood normally delivers about 5 mL of oxygen to the tissues.
2. pO2 falls from 104 mm Hg in alveoli to 40 mm Hg in deoxygenated blood, while pCO2 rises from 40 to 45 mm Hg.

Answer: (b) ERV + TV + RV + IRV

Explanation:
1. Total lung capacity is the sum of IRV, TV, ERV and RV.

Teacher's Note:
1. Inspiration is caused by contraction of the diaphragm and external intercostal muscles, which enlarge the thoracic volume; expiration is normally passive.
2. Know the lung volumes: TV 500 mL, IRV 2500-3000 mL, ERV 1000-1100 mL, RV 1100-1200 mL.

Answer: (d) Diaphragm

Explanation:
1. The diaphragm is the primary muscle of inspiration.

Teacher's Note:
1. Oxygen is carried mostly as oxyhaemoglobin (97 per cent) and CO2 mostly as bicarbonate (about 70 per cent).
2. Diffusion of gases depends on partial pressure gradient, solubility and thickness of the diffusion membrane.

Answer: (b) 104 mm Hg, 95 mm Hg

Explanation:
1. Alveolar air has pO2 of about 104 mm Hg and oxygenated blood about 95 mm Hg.

Teacher's Note:
1. Each 100 mL of oxygenated blood normally delivers about 5 mL of oxygen to the tissues.
2. pO2 falls from 104 mm Hg in alveoli to 40 mm Hg in deoxygenated blood, while pCO2 rises from 40 to 45 mm Hg.

Answer: (d) Both 1 and 2 are correct

Explanation:
1. CO2 is 20-25 times more soluble than O2, so a far larger amount of CO2 diffuses per unit pressure difference; statements 1 and 2 are both true.

Teacher's Note:
1. Inspiration is caused by contraction of the diaphragm and external intercostal muscles, which enlarge the thoracic volume; expiration is normally passive.
2. Know the lung volumes: TV 500 mL, IRV 2500-3000 mL, ERV 1000-1100 mL, RV 1100-1200 mL.

Answer: (d) All of these

Explanation:
1. The alveolar wall is a single cell thick, the diffusion membrane is far thinner than 1 mm and exchange is by simple diffusion.

Teacher's Note:
1. Oxygen is carried mostly as oxyhaemoglobin (97 per cent) and CO2 mostly as bicarbonate (about 70 per cent).
2. Diffusion of gases depends on partial pressure gradient, solubility and thickness of the diffusion membrane.

Answer: (a) About 97 per cent of O2 is transported by RBCs in the blood

Explanation:
1. About 97 per cent of O2 goes with haemoglobin in RBCs; only 20-25 per cent of CO2 is carried by RBCs and about 3 per cent of O2 and 7 per cent of CO2 is dissolved in plasma.

Teacher's Note:
1. Each 100 mL of oxygenated blood normally delivers about 5 mL of oxygen to the tissues.
2. pO2 falls from 104 mm Hg in alveoli to 40 mm Hg in deoxygenated blood, while pCO2 rises from 40 to 45 mm Hg.

Answer: (b) 5 ml

Explanation:
1. Under normal conditions 100 mL of oxygenated blood delivers about 5 mL of O2 to the tissues.

Teacher's Note:
1. Inspiration is caused by contraction of the diaphragm and external intercostal muscles, which enlarge the thoracic volume; expiration is normally passive.
2. Know the lung volumes: TV 500 mL, IRV 2500-3000 mL, ERV 1000-1100 mL, RV 1100-1200 mL.