NEET 2025 MCQ with Answer Explanation : Breathing and Exchange of Gases.

MCQ 21:
Which structure is responsible for the production of sound in the human body?

A) Trachea

B) Larynx

C) Pharynx

D) Bronchi

Answer: B) Larynx

Explanation: The larynx, or voice box, contains vocal cords and is responsible for sound production during speaking and singing.

MCQ 22:
What is the term for the maximum amount of air that can be inhaled after a normal tidal expiration?

A) Vital capacity

B) Inspiratory reserve volume

C) Expiratory reserve volume

D) Total lung capacity

Answer: B) Inspiratory reserve volume

Explanation: Inspiratory reserve volume is the additional air that can be inhaled beyond the normal tidal volume after a normal expiration.

MCQ 23:
The exchange of gases between the blood and tissues is known as:

A) External respiration

B) Internal respiration

C) Cellular respiration

D) Alveolar respiration

Answer: B) Internal respiration

Explanation: Internal respiration refers to the exchange of gases between blood and body tissues.

MCQ 24:
What happens to the diaphragm during exhalation?

A) It contracts and moves downwards.

B) It relaxes and moves upwards.

C) It remains stationary.

D) It changes shape.

Answer: B) It relaxes and moves upwards.

Explanation: During exhalation, the diaphragm relaxes and moves upwards, decreasing the volume of the thoracic cavity and forcing air out of the lungs.

MCQ 25:
Which of the following is a common symptom of respiratory diseases?

A) Nausea

B) Coughing

C) Abdominal pain

D) Skin rash

Answer: B) Coughing

Explanation: Coughing is a common symptom of respiratory diseases, helping to clear the airways of mucus and irritants.

MCQ 26:
The pleural cavity contains:

A) Air

B) Blood

C) Serous fluid

D) Lymph

Answer: C) Serous fluid

Explanation: The pleural cavity contains serous fluid, which lubricates the surfaces of the pleura and reduces friction during breathing.

MCQ 27:
What is the condition characterized by the destruction of alveoli?

A) Asthma

B) Emphysema

C) Chronic bronchitis

D) Pneumonia

Answer: B) Emphysema

Explanation: Emphysema is a chronic lung condition characterized by the destruction of alveoli, leading to difficulty in breathing.

MCQ 28:
Which of the following factors does NOT affect the rate of gas exchange?

A) Surface area of alveoli

B) Thickness of respiratory membrane

C) Temperature

D) Speed of blood flow

Answer: D) Speed of blood flow

Explanation: While speed of blood flow can influence oxygen transport, the rate of gas exchange itself is primarily affected by surface area, membrane thickness, and concentration gradients.

MCQ 29:
Which component of air has the highest partial pressure at sea level?

A) Oxygen

B) Carbon dioxide

C) Nitrogen

D) Water vapor

Answer: C) Nitrogen

Explanation: At sea level, nitrogen has the highest partial pressure, making up about 78% of the atmosphere.

MCQ 30:
The primary method of carbon dioxide transport in the blood is:

A) Dissolved in plasma

B) Bound to hemoglobin

C) As bicarbonate ions

D) All of the above

Answer: D) All of the above

Explanation: Carbon dioxide is transported in the blood in three forms: dissolved in plasma, bound to hemoglobin, and primarily as bicarbonate ions.