Q: Dalton’s Law states that the total pressure of a gas mixture is the sum of the partial pressures of each gas. If atmospheric pressure is 760 mmHg and oxygen makes up 21% of the air, what is the partial pressure of oxygen ($$P_{O_2$}$$)?

$$P_{O_2$} = 0.21 \times 760 = 159.6$$ mmHg

Question 1

Which of the following best describes the function of surfactant in the alveoli, according to the Law of LaPlace ($$P = \frac{2T}{r}$$)?

Accepted Answer

It reduces surface tension, equalizing pressure between different sized alveoli and preventing collapse.

Question 2

A patient with emphysema has lungs that are easy to inflate but difficult to deflate. Which of the following best explains this phenomenon?

Accepted Answer

Emphysema destroys elastic fibers, reducing elastic recoil and making passive exhalation difficult.

Question 3

According to Boyle’s Law ($$P = \frac{1}{V}$$), what happens to the intrapulmonary pressure when the thoracic cavity volume increases during inspiration?

Accepted Answer

Intrapulmonary pressure decreases below atmospheric pressure.

Question 4

Which of the following is the correct sequence of airflow through the respiratory tract during inhalation?

Accepted Answer

Oral cavity → Pharynx → Larynx → Trachea → Bronchi → Alveoli

Question 5

A premature infant is experiencing respiratory distress syndrome (RDS). Which of the following best explains the underlying cause?

Accepted Answer

The infant's alveoli lack sufficient surfactant, increasing surface tension and causing alveolar collapse.

Question 6

Which of the following best describes the effect of an asthma attack on airflow, according to the equation $$Flow = \frac{\Delta P}{R}$$ and $$R = \frac{1}{r^4$}$$?

Accepted Answer

Airway radius decreases, resistance increases dramatically, and airflow decreases.

Question 7

Dalton’s Law states that the total pressure of a gas mixture is the sum of the partial pressures of each gas. If atmospheric pressure is 760 mmHg and oxygen makes up 21% of the air, what is the partial pressure of oxygen ($$P_{O_2$}$$)?

Accepted Answer

$$P_{O_2$} = 0.21 	imes 760 = 159.6$$ mmHg

Question 8

Which of the following best explains why hyperventilation can lead to respiratory alkalosis?

Accepted Answer

Hyperventilation decreases CO2 levels, decreasing H+ and raising pH.

Question 9

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

Accepted Answer

Gas exchange between air and blood

Question 10

A patient is exposed to cyanide, which blocks cellular use of oxygen. What type of hypoxia does this patient experience?

Accepted Answer

Histotoxic hypoxia

Question 11

Which of the following best describes the effect of increased temperature on the oxygen-hemoglobin dissociation curve?

Accepted Answer

The curve shifts to the right, decreasing hemoglobin's affinity for oxygen.

Question 12

Which of the following equations correctly represents the carbonic acid-bicarbonate buffer system in the blood?

Accepted Answer

$$CO_2 + H_2O$$ \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + $$HCO_3$$^-$$

Question 13

Which respiratory center is primarily responsible for setting the basic rhythm of breathing?

Accepted Answer

Ventral Respiratory Group (VRG)

Question 14

Which of the following best describes the effect of a pneumothorax on lung function?

Accepted Answer

It eliminates the vacuum between the pleural membranes, causing lung collapse.

Question 15

Which of the following best explains why CO2 is a more powerful regulator of breathing than O2 under normal conditions?

Accepted Answer

CO2 crosses the blood-brain barrier, forms H+ in the CSF, and stimulates central chemoreceptors.

Question 16

Which of the following is a correct calculation for Vital Capacity (VC) using respiratory volumes?

Accepted Answer

$$VC = IRV + TV + ERV$$

Question 17

Which of the following best describes the chloride shift in red blood cells during CO2 transport?

Accepted Answer

Chloride ions enter the RBC as bicarbonate leaves.

Question 18

Which of the following would most likely occur during forced expiration, such as blowing out a candle?

Accepted Answer

Contraction of the internal intercostals and abdominal muscles

Question 19

Which of the following best explains why a person with fibrosis has decreased lung compliance?

Accepted Answer

Fibrosis increases scar tissue, making the lungs stiffer and harder to inflate.

The Respiratory System: Structure, Function, and Physiology

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