Free Respiratory System MCQs with Answers
40 Respiratory System MCQs from Anatomy and Physiology for Nursing, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
The respiratory system includes the air passages, lungs, pleura, alveoli and the mechanics of breathing. It explains pulmonary ventilation, gas exchange, oxygen and carbon dioxide transport, regulation of breathing, and the difference between external respiration in the lungs and internal respiration in body tissues.
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40 questions · page 2 of 2
21. Which structure is the main site of gas exchange between inspired air and pulmonary capillary blood?
- A. Terminal bronchioles
- B. Alveolar sacs
- C. Laryngeal cavity
- D. Main bronchi
Explanation: Alveolar sacs contain thin-walled alveoli surrounded by pulmonary capillaries, allowing rapid diffusion of gases.
Correct answer: Alveolar sacs- A. It decreases thoracic volume
- B. It increases thoracic volume
- C. It closes the small bronchioles
- D. It increases pressure inside the lungs
Explanation: When the diaphragm contracts, it flattens and increases the volume of the thoracic cavity.
Correct answer: It increases thoracic volume- A. Air inhaled during a normal breath
- B. Air exhaled after a normal breath
- C. Air remaining after maximal exhalation
- D. Air moved during forced inspiration
Explanation: Residual volume is the air that remains in the lungs after the strongest possible exhalation.
Correct answer: Air remaining after maximal exhalation- A. 2 litres per minute
- B. 4 litres per minute
- C. 6 litres per minute
- D. 12 litres per minute
Explanation: Minute ventilation equals respiratory rate multiplied by tidal volume: 12 × 500 mL = 6000 mL, or 6 litres per minute.
Correct answer: 6 litres per minute- A. Pulmonary artery
- B. Pulmonary vein
- C. Aorta
- D. Superior vena cava
Explanation: The pulmonary artery carries deoxygenated blood from the right ventricle to the pulmonary capillaries.
Correct answer: Pulmonary artery- A. Breathe rapidly through the mouth
- B. Use pursed-lip breathing during exhalation
- C. Hold the breath after every inspiration
- D. Lie flat and breathe shallowly
Explanation: Pursed-lip breathing creates slight back pressure during exhalation and helps keep narrowed airways open longer.
Correct answer: Use pursed-lip breathing during exhalation- A. Diaphragm
- B. Internal intercostal muscle
- C. Abdominal muscle
- D. Sternocleidomastoid muscle
Explanation: The diaphragm is the primary muscle used during quiet inspiration. The accessory muscles, including the sternocleidomastoid, are recruited…
Correct answer: Diaphragm- A. Respiratory rate of 30 per minute
- B. Mild dryness of the lips
- C. Reduced appetite at breakfast
- D. Difficulty sleeping overnight
Explanation: Tachypnoea with shallow breathing may indicate inadequate ventilation and developing hypoxaemia, so it requires prompt assessment and…
Correct answer: Respiratory rate of 30 per minute- A. A fall in arterial carbon dioxide
- B. A rise in arterial carbon dioxide
- C. A rise in blood oxygen above normal
- D. A fall in body temperature
Explanation: A rise in arterial carbon dioxide increases hydrogen ion concentration and stimulates respiratory centres to increase ventilation.
Correct answer: A rise in arterial carbon dioxide- A. Uvula
- B. Epiglottis
- C. Soft palate
- D. Vocal cord
Explanation: The epiglottis folds downward over the laryngeal opening during swallowing.
Correct answer: Epiglottis- A. It becomes lower than atmospheric pressure
- B. It becomes equal to venous pressure
- C. It becomes higher than atmospheric pressure
- D. It becomes equal to pleural pressure
Explanation: During quiet expiration, the respiratory muscles relax and elastic recoil decreases lung volume.
Correct answer: It becomes higher than atmospheric pressure- A. Tidal ventilation
- B. Alveolar ventilation
- C. Residual ventilation
- D. Inspiratory reserve
Explanation: Alveolar ventilation is the volume of fresh air reaching the alveoli each minute after dead-space air is excluded.
Correct answer: Alveolar ventilation- A. 1,800 mL
- B. 4,200 mL
- C. 6,000 mL
- D. 7,800 mL
Explanation: Alveolar ventilation equals (tidal volume minus dead space) multiplied by respiratory rate: (500 minus 150) × 12 = 4,200 mL per minute.
Correct answer: 4,200 mL- A. Parietal pleura
- B. Visceral pleura
- C. Mediastinal fascia
- D. Endothoracic fascia
Explanation: The visceral pleura closely covers the lungs and enters the fissures between lobes.
Correct answer: Visceral pleura- A. Respiratory alkalosis
- B. Metabolic alkalosis
- C. Respiratory acidosis
- D. Metabolic acidosis
Explanation: Hypoventilation causes carbon dioxide retention, and carbon dioxide combines with water to increase carbonic acid.
Correct answer: Respiratory acidosis- A. Air in alveoli that receives no blood flow
- B. Air in conducting passages that does not exchange gases
- C. Air remaining after maximum forced expiration
- D. Air exchanged during normal quiet breathing
Explanation: Anatomical dead space includes air in the nose, pharynx, larynx, trachea and bronchi, where gas exchange does not occur.
Correct answer: Air in conducting passages that does not exchange gases- A. Expiratory wheezing
- B. Pulse rate of 104 beats per minute
- C. Silent chest with increasing drowsiness
- D. Mild anxiety about breathing
Explanation: A silent chest with drowsiness suggests severely reduced airflow and worsening respiratory failure, so airway and breathing take priority.
Correct answer: Silent chest with increasing drowsiness- A. Pulmonary artery
- B. Pulmonary vein
- C. Superior vena cava
- D. Bronchial artery
Explanation: Pulmonary veins carry oxygenated blood from the pulmonary capillaries to the left atrium.
Correct answer: Pulmonary vein- A. Loss of voluntary swallowing only
- B. Irregular or inadequate breathing
- C. Increased production of surfactant
- D. Improved response to carbon dioxide
Explanation: The medulla contains vital respiratory centres that generate and regulate the basic breathing rhythm.
Correct answer: Irregular or inadequate breathing- A. Haemoglobin releases more oxygen to the tissues
- B. Haemoglobin binds oxygen more strongly in the tissues
- C. Haemoglobin releases less oxygen to the tissues
- D. Haemoglobin stops carrying oxygen in the blood
Explanation: Increased temperature and carbon dioxide reduce haemoglobin's affinity for oxygen, shifting the oxyhaemoglobin dissociation curve to the…
Correct answer: Haemoglobin releases more oxygen to the tissues