MCAT - Organ Systems:: Respiratory System

Which structure prevents food and liquid from entering the trachea during swallowing?

- **A)** The uvula
- **B)** The epiglottis
- **C)** The vocal cords
- **D)** The cricoid cartilage

During quiet inspiration, contraction of the diaphragm increases thoracic volume primarily by:

- **A)** Flattening and descending, pulling the floor of the thoracic cavity downward
- **B)** Elevating the ribs via the external intercostal muscles only
- **C)** Contracting the abdominal muscles to pull the diaphragm up
- **D)** Actively expanding the lung parenchyma independent of the thoracic cage

Quiet expiration at rest is primarily:

- **A)** An active process driven by internal intercostal muscle contraction
- **B)** An active process driven by abdominal muscle contraction
- **C)** A passive process driven by elastic recoil of the lungs and chest wall
- **D)** Impossible without contraction of the diaphragm

Pulmonary surfactant, produced by type II pneumocytes, primarily functions to:

- **A)** Increase alveolar surface tension to keep alveoli rigid
- **B)** Transport oxygen across the alveolar-capillary membrane
- **C)** Kill inhaled pathogens within the alveoli
- **D)** Reduce alveolar surface tension, preventing alveolar collapse (atelectasis) and equalizing pressures between differently sized alveoli

Type I pneumocytes are best characterized by which feature?

- **A)** Thin, squamous cells that make up the majority of the alveolar surface and permit efficient gas diffusion
- **B)** Cuboidal cells that secrete surfactant
- **C)** Ciliated cells that propel mucus toward the pharynx
- **D)** Phagocytic cells that engulf inhaled particles

Tidal volume (TV) is best defined as:

- **A)** The maximum volume that can be forcibly exhaled after a maximal inhalation
- **B)** The volume of air inspired or expired in a single normal (quiet) breath
- **C)** The volume remaining in the lungs after a maximal exhalation
- **D)** The maximum additional volume that can be inhaled after a normal inspiration

Functional residual capacity (FRC) is the sum of which two lung volumes?

- **A)** Tidal volume + inspiratory reserve volume
- **B)** Inspiratory reserve volume + expiratory reserve volume
- **C)** Expiratory reserve volume + residual volume
- **D)** Tidal volume + residual volume

Residual volume (RV) cannot be measured directly by simple spirometry because:

- **A)** RV represents air that remains in the lungs and cannot be voluntarily exhaled, so it never crosses the spirometer
- **B)** Spirometers cannot measure any lung volume accurately
- **C)** RV only exists in patients with lung disease
- **D)** RV is highly variable and impossible to estimate by any method