Quiz: Pulmonary Ventilation — 25 questions

1. What is the primary purpose of respiration in the body?

A. To produce digestive enzymes and absorb nutrients

B. To supply tissues with oxygen and remove carbon dioxide

C. To regulate blood pressure and maintain body temperature

D. To generate hormones and distribute them through tissues

Answer: (B)

Explanation

Respiration supports tissue metabolism by delivering O2 and removing CO2 from the organism. Blood pressure regulation is related to circulation rather than the main purpose of respiration.

2. Which sequence best represents the major processes included in respiration?

A. Pulmonary ventilation, gas diffusion, blood transport, and ventilation regulation

B. Air humidification, mucus secretion, swallowing, and cardiac conduction

C. Cell division, hormone release, waste filtration, and immune activation

D. Blood filtration, nutrient absorption, muscle contraction, and heat production

Answer: (A)

Explanation

Respiration includes moving air, exchanging gases between alveoli and blood, transporting those gases, and regulating ventilation. Nutrient absorption and blood filtration are not listed as components of respiration.

3. A process moves air between the atmosphere and the alveoli without describing gas exchange across the alveolar wall; what is this process called?

A. Alveolar diffusion

B. Blood gas transport

C. Pulmonary ventilation

D. Ventilatory regulation

Answer: (C)

Explanation

Pulmonary ventilation is the movement of air into and out of the lungs between the atmosphere and alveoli. Diffusion refers instead to the exchange of O2 and CO2 between alveolar air and blood.

4. What mechanical change occurs during inspiration?

A. Thoracic volume decreases as the ribs descend and the diaphragm rises

B. Thoracic volume decreases while the diaphragm contracts upward

C. Thoracic volume stays constant while alveolar gas is exchanged

D. Thoracic volume increases as the ribs elevate and the diaphragm descends

Answer: (D)

Explanation

Inspiratory muscle contraction elevates the ribs and lowers the diaphragm, increasing thoracic volume and drawing air into the lungs. Decreasing thoracic volume describes active expiration rather than inspiration.

5. During quiet breathing, what approximate shares of lung volume change are associated with the external intercostal muscles and the diaphragm?

A. About 10% from the external intercostals and 90% from the diaphragm

B. About 75% from the external intercostals and 25% from the diaphragm

C. About 50% from the external intercostals and 50% from the diaphragm

D. About 25% from the external intercostals and 75% from the diaphragm

Answer: (D)

Explanation

External intercostal contraction contributes approximately 25% of the lung volume change, whereas diaphragm contraction accounts for approximately 75% of air movement. Reversing these proportions reflects the documented misconception.

6. Which pressure is approximately $-5\ \mathrm{cmH_2O}$ at rest and becomes about $-7.5\ \mathrm{cmH_2O}$ during inspiration?

A. Pleural pressure

B. Alveolar pressure

C. Atmospheric pressure

D. Transpulmonary pressure

Answer: (A)

Explanation

Pleural pressure is the pressure in the fluid-filled space between the visceral and parietal pleura and remains negative during these phases. Alveolar pressure is approximately $0\ \mathrm{cmH_2O}$ when there is no airflow.

7. How does alveolar pressure change during a normal breathing cycle?

A. It is negative without airflow, positive during inspiration, and negative during expiration

B. It is zero without airflow, negative during inspiration, and positive during expiration

C. It remains zero during inspiration and expiration because airflow does not alter it

D. It is positive without airflow, negative during inspiration, and zero during expiration

Answer: (B)

Explanation

Alveolar pressure is $0\ \mathrm{cmH_2O}$ without airflow, falls to $-1\ \mathrm{cmH_2O}$ during inspiration, and rises to $+1\ \mathrm{cmH_2O}$ during expiration. The pressure changes create the gradients that drive airflow.

8. If alveolar pressure is $+1\ \mathrm{cmH_2O}$ and pleural pressure is $-7.5\ \mathrm{cmH_2O}$, what is the transpulmonary pressure?

A. $-8.5\ \mathrm{cmH_2O}$

B. $+7.5\ \mathrm{cmH_2O}$

C. $-6.5\ \mathrm{cmH_2O}$

D. $+8.5\ \mathrm{cmH_2O}$

Answer: (D)

Explanation

Using $P_{el}=P_{alv}-P_{pl}$ gives $1-(-7.5)=+8.5\ \mathrm{cmH_2O}$. Subtracting the magnitudes instead would incorrectly ignore that pleural pressure is negative.

9. A lung with normal compliance receives approximately how much additional air for each $1\ \mathrm{cmH_2O}$ increase in transpulmonary pressure?

A. Approximately 1,000 ml

B. Approximately 200 ml

C. Approximately 20 ml

D. Approximately 500 ml

Answer: (B)

Explanation

Normal lung compliance is approximately 200 ml of added air per $1\ \mathrm{cmH_2O}$ increase in transpulmonary pressure. A value such as 500 ml confuses a typical breath volume with compliance.

10. Which statement best defines pulmonary surfactant?

A. A contractile substance secreted by smooth muscle cells in bronchioles

B. A connective-tissue substance released by capillary endothelial cells

C. A mucus-like substance produced by ciliated cells in the trachea

D. A surface-active substance secreted by type II alveolar epithelial cells

Answer: (D)

Explanation

Pulmonary surfactant is secreted by type II alveolar epithelial cells and markedly lowers the surface tension of alveolar fluid. Untreated alveolar fluid has the opposite effect because it increases the tendency of alveoli to collapse.

11. For an alveolus described by $P=\frac{2T}{r}$, what happens to the pressure generated by surface tension when its radius decreases while surface tension remains constant?

A. The pressure remains constant because radius does not affect surface tension

B. The pressure becomes zero because the alveolar volume becomes smaller

C. The pressure increases because pressure varies inversely with radius

D. The pressure decreases because a smaller radius reduces the numerator

Answer: (C)

Explanation

The equation shows that pressure is inversely proportional to alveolar radius, so reducing the radius raises the pressure generated by surface tension. A smaller radius therefore increases, rather than decreases, the collapsing pressure.

12. Which surface-tension value is characteristic of alveolar fluid containing surfactant?

A. Approximately 0.005–0.030 N/m

B. Approximately 0.072 N/m

C. Approximately 0.050 N/m

D. Approximately 0.200 N/m

Answer: (A)

Explanation

Surfactant lowers alveolar-fluid surface tension to approximately 0.005–0.030 N/m. The higher values represent alveolar fluid without surfactant or pure water, not normal surfactant-containing fluid.

13. Which description correctly compares the phases of normal breathing?

A. Both inspiration and expiration are passive because pressure changes occur naturally

B. Both inspiration and expiration are active because each requires muscular work

C. Inspiration is passive, whereas expiration is active because of muscle contraction

D. Inspiration is active, whereas expiration is passive because of elastic recoil

Answer: (D)

Explanation

Normal inspiration requires muscular work and is therefore active, while normal expiration results from elastic forces of the lungs and chest wall. Expiration can become active during forced breathing, but that is not the normal resting pattern.

14. Which set lists the three components of inspiratory work?

A. Work against gravity, blood viscosity, and alveolar diffusion

B. Work against surface tension, oxygen transport, and chest-wall weight

C. Work against pulmonary blood flow, cardiac output, and airway pressure

D. Work against elastic forces, tissue resistance, and airway resistance

Answer: (D)

Explanation

Inspiratory work is divided into work against elastic forces, tissue resistance, and airway resistance. The other combinations include physiological factors that are not the three listed components of inspiratory work.

15. What does spirometry directly record?

A. The volume of air entering and leaving the lungs

B. The oxygen concentration in pulmonary capillary blood

C. The pressure gradient across the pleural membranes

D. The diffusion rate of carbon dioxide across alveolar walls

Answer: (A)

Explanation

Spirometry records the volumes of air moving into and out of the lungs, producing a spirogram. A spirogram is the resulting record, not the measurement process itself.

16. Which list contains the four pulmonary volumes?

A. Tidal capacity, inspiratory capacity, expiratory capacity, and residual capacity

B. Minute volume, anatomic dead space, alveolar ventilation, and total lung capacity

C. Tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume

D. Inspiratory capacity, functional residual capacity, vital capacity, and total lung capacity

Answer: (C)

Explanation

The four pulmonary volumes are tidal volume, inspiratory reserve volume, expiratory reserve volume, and residual volume. Inspiratory capacity, functional residual capacity, vital capacity, and total lung capacity are capacities formed by combining volumes.

17. Using tidal volume of 500 ml and inspiratory reserve volume of 3000 ml, what is the inspiratory capacity?

A. 3500 ml

B. 5800 ml

C. 4600 ml

D. 2300 ml

Answer: (A)

Explanation

Inspiratory capacity is calculated as $IC=TV+IRV$, so $IC=500+3000=3500\ \mathrm{ml}$. The other values correspond to different pulmonary capacities: functional residual capacity, vital capacity, and total lung capacity.

18. Which pulmonary capacity represents the air remaining in the lungs after a normal expiration?

A. Total lung capacity

B. Vital capacity

C. Inspiratory capacity

D. Functional residual capacity

Answer: (D)

Explanation

Functional residual capacity is the volume remaining after normal expiration and equals $FRC=ERV+RV=2300\ \mathrm{ml}$. Vital capacity instead represents the volume expelled after maximal inspiration, so it describes a different maneuver.

19. Which structures are included among the gas-exchange areas reached by alveolar ventilation?

A. Trachea, bronchi, terminal bronchioles, and conducting bronchioles

B. Alveoli, alveolar ducts, alveolar sacs, and respiratory bronchioles

C. Nasal cavity, pharynx, larynx, and trachea

D. Pleural cavity, alveoli, pulmonary arteries, and bronchi

Answer: (B)

Explanation

Alveolar ventilation delivers new air to the alveoli, alveolar ducts, alveolar sacs, and respiratory bronchioles, where gas exchange can occur. Conducting passages such as the trachea and larger bronchi belong to anatomical dead space rather than the gas-exchange areas.

20. What is the approximate volume of anatomical dead space in a typical adult?

A. About 150 ml

B. About 50 ml

C. About 1,000 ml

D. About 500 ml

Answer: (A)

Explanation

Anatomical dead space is the volume of the conducting airways that do not participate in gas exchange, and it is approximately 150 ml. A value near 500 ml is more representative of a typical tidal volume, not anatomical dead space.

21. Which condition contributes to physiological dead space without being part of anatomical dead space?

A. Alveoli that receive air but have absent or insufficient perfusion

B. Conducting airways that transport air without participating in gas exchange

C. Respiratory bronchioles that connect conducting and gas-exchange regions

D. Alveolar ducts that receive newly inhaled air during inspiration

Answer: (A)

Explanation

Physiological dead space includes anatomical dead space plus alveoli that are ventilated but poorly perfused or unperfused. Conducting airways are part of anatomical dead space, whereas insufficiently perfused alveoli add the alveolar component.

22. If respiratory frequency is 12 breaths per minute, tidal volume is 500 ml, and dead-space volume is 150 ml, what is the minute alveolar ventilation?

A. $1{,}800\ \mathrm{ml/min}$

B. $4{,}200\ \mathrm{ml/min}$

C. $5{,}850\ \mathrm{ml/min}$

D. $6{,}000\ \mathrm{ml/min}$

Answer: (B)

Explanation

Minute alveolar ventilation is calculated as $V_A=f\times(V_T-V_D)=12\times(500-150)=4{,}200\ \mathrm{ml/min}$. Multiplying frequency by the full tidal volume gives minute ventilation, which does not subtract the air remaining in dead space.

23. How does structural support differ between the bronchi and bronchioles?

A. Smooth muscle supports the bronchi, while bronchioles retain cartilage throughout their walls.

B. Cartilage supports the bronchioles, while the bronchi remain open through surfactant action.

C. Cartilage supports the bronchi, while bronchioles lack cartilage and rely mainly on transpulmonary pressure.

D. Bronchi and bronchioles both retain cartilage, but bronchioles contain fewer cartilage plates.

Answer: (C)

Explanation

Cartilage keeps the conducting airways open from the trachea through the bronchi, but it disappears completely in the bronchioles, which depend mainly on transpulmonary pressure. The presence of smooth muscle does not mean that bronchioles retain cartilage.

24. Which autonomic pattern correctly describes regulation of bronchiolar diameter?

A. Vagal acetylcholine dilates bronchi, whereas norepinephrine and epinephrine produce bronchiolar constriction.

B. Beta-adrenergic stimulation by norepinephrine or epinephrine dilates bronchi, whereas vagal acetylcholine causes constriction.

C. Norepinephrine causes bronchiolar constriction, whereas epinephrine and acetylcholine both dilate bronchi.

D. Beta-adrenergic stimulation constricts bronchi, whereas vagal acetylcholine produces marked bronchiolar dilation.

Answer: (B)

Explanation

Sympathetic norepinephrine and epinephrine act on beta-adrenergic receptors to dilate the bronchi, while parasympathetic vagal acetylcholine causes mild to moderate bronchiolar constriction. The opposite autonomic pattern reverses the established effects of these pathways.

25. How does the mucociliary clearance system remove inhaled particles from the airways?

A. Goblet-cell and glandular mucus traps particles, and cilia move it toward the pharynx for swallowing or coughing.

B. Cartilage captures particles, and smooth muscle contractions propel them toward the lungs for removal.

C. Submucosal glands dissolve particles, and cilia transport them into pulmonary blood vessels.

D. Alveolar macrophages release mucus, and cilia move the material toward the alveoli for gas exchange.

Answer: (A)

Explanation

Mucus from goblet cells and submucosal glands traps inhaled particles, while cilia beat approximately 20 times per second to move the mucus toward the pharynx. Alveolar macrophages have a separate defense role, and airway mucus is not transported into the alveoli or blood vessels.