The volume of air that can be inspired forcefully after a normal inspiration is called:

 # The volume of air that can be inspired forcefully after a normal inspiration is called:

A. Residual Volume (RV)

B. Tidal Volume (TV)

C. Expiratory Reserve Volume (ERV)

D. Inspiratory Reserve Volume (IRV)

The correct answer is D. Inspiratory Reserve Volume (IRV).

The Inspiratory Reserve Volume (IRV) is the volume of air that can be forcefully inspired after a normal inspiration (tidal volume). It represents the additional air that can be taken into the lungs beyond a typical breath.

• A. Residual Volume (RV): The volume of air remaining in the lungs after a maximal expiration.
• B. Tidal Volume (TV): The volume of air inhaled or exhaled during normal breathing.
• C. Expiratory Reserve Volume (ERV): The volume of air that can be forcefully exhaled after a normal expiration.

The partial pressure of oxygen (pO2) in the alveoli is approximately:

 # The partial pressure of oxygen (pO2) in the alveoli is approximately:

A. 40 mm Hg

B. 160 mm Hg

C. 104 mm Hg

D. 95 mm Hg

The correct answer is C. 104 mm Hg.

The partial pressure of oxygen (pO₂) in the alveoli is approximately 104 mm Hg under normal conditions. This value is calculated based on the atmospheric pressure (760 mm Hg at sea level), the fraction of oxygen in inspired air (about 21%), and adjustments for water vapor pressure (47 mm Hg at body temperature) and the effects of carbon dioxide and nitrogen in the alveoli. The alveolar pO₂ is lower than the atmospheric pO₂ (about 160 mm Hg) due to these factors.

Which of the following structures is not part of the conducting zone of the respiratory system?

 # Which of the following structures is not part of the conducting zone of the respiratory system?

 A. Trachea

 B. Main bronchi

C. Alveolar duct

D. Pharynx

The correct answer is C. Alveolar duct.

The conducting zone of the respiratory system includes structures that facilitate the movement of air into and out of the lungs but are not directly involved in gas exchange. These structures include the pharynx, trachea, main bronchi, and other bronchi and bronchioles up to the terminal bronchioles. The alveolar duct, however, is part of the respiratory zone, where gas exchange occurs, as it leads to the alveoli.