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Free Human Respiratory System MCQs with Answers

146 Human Respiratory System MCQs from Biology, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

The human respiratory system conducts air to the alveoli, where oxygen and carbon dioxide exchange occurs across thin respiratory surfaces. Questions cover the nasal passage, trachea, bronchi, lungs, diaphragm and intercostal muscles, ventilation mechanics and gas transport, while distinguishing breathing and gaseous exchange from cellular respiration.

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146 questions · page 8 of 8

141. Percentage of CO2 carried by plasma proteins is:

  • A. 5%
  • B. 6%
  • C. 7%
  • D. 8%

Explanation: Carbon dioxide (CO2) is transported in the blood in three main forms. Approximately 7% of CO2 is transported bound to plasma proteins…

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Correct answer: 7%

142. If a new born baby possesses carboxyhemoglobin instead of the oxyhemoglobin, the condition may be:

  • A. Embolism
  • B. Atherosclensis
  • C. Cyanosis
  • D. Arteriosclerosis

Explanation: Cyanosis indicates there may be decreased oxygen attached to red blood cells in the bloodstream.

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Correct answer: Cyanosis

143. Each nasal cavity is lined with mocous membrane of:

  • A. Flagellated endothelium
  • B. Flagellated epithelium
  • C. Ciliated epithelium
  • D. All of the above

Explanation: The nasal cavity is lined with a mucous membrane that contains a specialized type of epithelium called ciliated epithelium.

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Correct answer: Ciliated epithelium

144. Presence of cartilaginous ring in respiratory tract act as:

  • A. Support
  • B. Keep passage open
  • C. Prevent collapsing
  • D. All of the above

Explanation: A. Support: The rings provide structural support to the trachea and bronchi, helping to maintain their shape and prevent collapse during…

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Correct answer: All of the above

145. The lateral walls of the chest cavity of man are composed of the:

  • A. Ribs and trachea
  • B. Intercostal muscles
  • C. Ribs & intercostal muscles
  • D. Ribs, intercostal muscles & diaphragm

Explanation: Option C, "Ribs & intercostal muscles," is the correct answer. The lateral walls of the chest cavity in humans are primarily composed of…

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Correct answer: Ribs & intercostal muscles

146. Where does the Trachea lie in relation to the esophagus?

  • A. Dorsal
  • B. Ventral
  • C. Medial
  • D. Lateral

Explanation: The trachea (windpipe) is located ventral (in front of) the esophagus in the thoracic cavity.

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Correct answer: Ventral
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