Q: Which of the following is the correct calculation for the partial pressure of oxygen in humid air at 25°C, given atmospheric pressure is 760 mm Hg, water vapor pressure is 24 mm Hg, and oxygen is 21% of the air?

$$P_{O_2$} = (760 - 24) \times 0.21 = 155 mm Hg$$

Q: A patient has a tidal volume of 500 mL, a respiratory rate of 12 breaths/min, and an anatomic dead space of 150 mL. What is their alveolar ventilation per minute?

$$Alveolar\ ventilation = 12 \times (500 - 150) = 4200 mL/$$min

Question 1

Which of the following best describes the primary function of Type II alveolar cells in the lungs?

Accepted Answer

They produce surfactant to reduce surface tension in the alveoli.

Question 2

According to Boyle's Law, what happens to the pressure inside the lungs if the lung volume doubles, assuming temperature and the number of gas molecules remain constant?

Accepted Answer

The pressure is halved.

Question 3

A patient with pulmonary fibrosis has difficulty inflating their lungs. Which property of the lungs is most affected in this condition?

Accepted Answer

Lung compliance

Question 4

Which equation correctly represents the Law of LaPlace as it applies to alveoli?

Accepted Answer

$$P = 2T/r$$

Question 5

A person inhales deeply, increasing their thoracic cavity volume. According to the ideal gas law, what happens to the alveolar pressure during this process?

Accepted Answer

Alveolar pressure decreases below atmospheric pressure.

Question 6

Which of the following is the correct calculation for the partial pressure of oxygen in humid air at 25°C, given atmospheric pressure is 760 mm Hg, water vapor pressure is 24 mm Hg, and oxygen is 21% of the air?

Accepted Answer

$$P_{O_2$} = (760 - 24) 	imes 0.21 = 155 mm Hg$$

Question 7

Which of the following changes would most likely increase airway resistance and decrease airflow to the alveoli?

Accepted Answer

Bronchoconstriction due to parasympathetic stimulation

Question 8

A spirometry test shows a patient has a reduced forced expiratory volume in 1 second (FEV1) but a normal forced vital capacity (FVC). What type of lung disease does this pattern suggest?

Accepted Answer

Obstructive lung disease

Question 9

Which of the following best explains why pulmonary circulation is considered 'high flow, low pressure' compared to systemic circulation?

Accepted Answer

The pulmonary circuit has shorter blood vessel length.

Question 10

A premature infant is diagnosed with newborn respiratory distress syndrome (NRDS). Which of the following is the primary physiological problem in this condition?

Accepted Answer

Inadequate production of surfactant

Question 11

During quiet breathing, what is the primary muscle responsible for inspiration?

Accepted Answer

Diaphragm

Question 12

Which of the following best describes the effect of surfactant on alveolar surface tension and the work of breathing?

Accepted Answer

Surfactant decreases surface tension, making breathing easier.

Question 13

A patient has a tidal volume of 500 mL, a respiratory rate of 12 breaths/min, and an anatomic dead space of 150 mL. What is their alveolar ventilation per minute?

Accepted Answer

$$Alveolar\ ventilation = 12 	imes (500 - 150) = 4200 mL/$$min

Question 14

Which of the following is NOT a function of the respiratory system?

Accepted Answer

Synthesis of plasma proteins

Question 15

If the intrapleural pressure becomes equal to atmospheric pressure, what is the most likely consequence?

Accepted Answer

The lungs will collapse (pneumothorax).

Question 16

Which of the following best describes the relationship between airway diameter and airway resistance?

Accepted Answer

As airway diameter decreases, airway resistance increases.

Question 17

A person is exposed to a high altitude where atmospheric pressure is 600 mm Hg and oxygen makes up 21% of the air. What is the partial pressure of oxygen ($$P_{O_2$}) in $$this environment?

Accepted Answer

$$P_{O_2$} = 600 	imes 0.21 = 126 mm Hg$$

Question 18

Which of the following best explains why fresh air entering the lungs during inspiration is only about 10% of the total lung volume at the end of inspiration?

Accepted Answer

Most of the air in the lungs is residual air that does not participate in gas exchange.

Question 19

Which of the following formulas correctly calculates total pulmonary ventilation?

Accepted Answer

$$Total\ pulmonary\ ventilation = ventilation\ rate 	imes tidal\ volume$$

Question 20

Which of the following best describes the effect of sympathetic stimulation on airway smooth muscle?

Accepted Answer

It causes bronchodilation by relaxing smooth muscle via $$\$$beta_2$$ receptors.

Mechanics of Breathing: Structure, Function, and Gas Laws of the Respiratory System

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