Free Respiration MCQs with Answers

• A. alveoli
• B. bronchi
• C. trachea
• D. larynx

Explanation: The millions of thin walled alveoli provide the enormous surface where oxygen enters the blood and carbon dioxide leaves.

• A. pharynx
• B. larynx
• C. trachea
• D. nasal cavity

Explanation: The larynx houses the vocal cords, which vibrate as air passes to produce sound.

• A. trachea
• B. larynx
• C. pharynx
• D. bronchus

Explanation: The pharynx receives air from the nose and food from the mouth and directs them onwards, which is why swallowing must temporarily close…

• A. alveoli
• B. alveolar ducts
• C. pleural sacs
• D. two bronchi

Explanation: Each primary bronchus enters a lung and branches into ever finer bronchioles ending in alveoli.

• A. pleura
• B. pericardium
• C. peritoneum
• D. meninges

Explanation: The pleura secretes fluid that lets the lungs slide smoothly against the chest wall during breathing.

• A. 6 per minute
• B. 16 per minute
• C. 40 per minute
• D. 75 per minute

Explanation: Quiet breathing runs at roughly 12 to 20 cycles per minute, around 16. The figure 75 per minute belongs to the heart rate, and examiners…

• A. the abdominal muscles only
• B. the internal intercostal muscles only
• C. the external intercostal muscles
• D. the smooth muscles of the alveoli

Explanation: The external intercostals lift the rib cage up and out, enlarging the thorax with the diaphragm's downward pull.

• A. glomeruli
• B. villi
• C. cisternae
• D. alveoli

Explanation: Alveoli hang in grape like clusters at the end of the airways, each wrapped in capillaries.

• A. nasal cavity
• B. trachea only
• C. bronchi
• D. alveoli

Explanation: Hairs and mucus trap particles while blood vessels warm the air and secretions humidify it before it reaches delicate lung tissue.

• A. fluid filling the alveoli
• B. constriction of the bronchi and bronchioles with excess mucus
• C. destruction of the cartilage rings of the trachea
• D. paralysis of the diaphragm

Explanation: The airway smooth muscle contracts and the lining swells with mucus, narrowing the tubes so air whistles through.

• A. the blood actively pumps it in
• B. the alveolar walls are impermeable to nitrogen
• C. the partial pressure of oxygen is higher in the alveoli than in the blood
• D. plasma proteins pull it across

Explanation: Gases always diffuse down their partial pressure gradients, and incoming alveolar air carries more oxygen than the arriving deoxygenated…

• A. dissolved in the plasma
• B. as bicarbonate ions
• C. as carboxyhaemoglobin
• D. bound to haemoglobin inside red blood cells

Explanation: About 97 per cent of oxygen rides on haemoglobin as oxyhaemoglobin, while only a small fraction dissolves in plasma.

• A. carbonic anhydrase
• B. catalase
• C. amylase
• D. decarboxylase

Explanation: Carbonic anhydrase makes carbonic acid form rapidly, which then dissociates to bicarbonate and H+, the main vehicle for CO2 transport.

• A. external respiration
• B. internal respiration
• C. breathing
• D. ventilation

Explanation: Internal, or tissue, respiration is gas exchange at the cells, while external respiration happens at the lungs.

• A. alveolar air
• B. arterial blood
• C. respiring tissues
• D. pulmonary vein

Explanation: Cells produce CO2 continuously, so its pressure peaks in the tissues and falls stepwise into venous blood, alveoli and finally the expired…

• A. releases carbon dioxide and binds more oxygen
• B. is destroyed by the cells
• C. holds its oxygen more tightly
• D. releases oxygen and picks up carbon dioxide

Explanation: Low oxygen pressure and high CO2 in the tissues make haemoglobin surrender oxygen and take on CO2 and H+, reversing what happened in the…

• A. It is dry and thick
• B. It is thin
• C. It is kept moist
• D. It has a large surface area

Explanation: Gases must dissolve before diffusing, and distance must be tiny, so efficiency demands a moist, thin, extensive surface.

• A. one cell layer
• B. two cell layers
• C. four cell layers
• D. eight cell layers

Explanation: Only the single alveolar epithelium and the single capillary endothelium stand in the way, a combined thickness of about one micrometre.

• A. from the alveolar air into the blood
• B. from red blood cells into haemoglobin
• C. from the blood into the alveolar air
• D. from the plasma into the lymph

Explanation: Venous blood arrives with a higher CO2 pressure than alveolar air, so the gas diffuses out to be exhaled.

• A. nicotine
• B. carbon monoxide
• C. ash
• D. tar

Explanation: Tar condenses in the airways and contains the chemicals that mutate DNA and cause cancer, while nicotine addicts and carbon monoxide…