Respiratory System — Multiple Choice

What process describes gas exchange between alveoli and pulmonary blood?

C. External respiration

What structure serves as the primary site of gas exchange in the lungs?

B. Alveoli

Which structure prevents food from entering the trachea during swallowing?

C. Epiglottis

What does Boyle’s law state?

C. Pressure varies inversely with volume at constant temperature

Which pressure keeps the lungs inflated under normal conditions?

D. Transpulmonary pressure

Which hormone or signal dilates bronchioles during an asthma attack?

C. Epinephrine

Which cells produce surfactant in the alveoli?

B. Type II alveolar cells

What happens to air pressure inside the lungs during inspiration?

C. It drops below atmospheric pressure

Which condition results from a loss of negative pressure in the pleural cavity?

C. Lung collapse

What is the primary chemical stimulus for breathing?

B. High carbon dioxide

What is the function of the epiglottis?

C. Prevents food from entering the larynx

Which respiratory structure is responsible for voice production?

C. Larynx

What determines the pitch of your voice?

A. Length and tension of the vocal cords

Which of the following is a role of the nasal conchae?

C. Filter, warm, and moisten air

What is the major function of surfactant?

C. Reduce surface tension in alveoli

What happens if type II alveolar cells are deficient in newborns?

B. Infant respiratory distress syndrome

What is anatomical dead space?

B. Volume of air that doesn’t participate in gas exchange

Which pressure is always negative and helps prevent lung collapse?

C. Intrapleural pressure

What are the conducting zone structures responsible for?

C. Air filtration and movement to respiratory zone

What structure connects the respiratory and digestive systems?

D. Pharynx

What are the two layers of pleura surrounding the lungs?

B. Visceral and parietal

What is the primary function of the trachealis muscle?

C. Controls diameter of trachea during coughing

What volume of air remains in the lungs after a forced exhalation?

B. Residual volume

What is total lung capacity (TLC)?

B. Maximum amount of air lungs can hold

What effect does fibrosis have on lung compliance?

C. Decreases compliance

What is the function of the nasal mucosa?

A. Humidify and filter air

Why do bronchioles have more smooth muscle than bronchi?

C. To control airflow resistance

Which of the following contributes to voice loudness?

B. Air pressure from lungs

What structure helps equalize air pressure throughout the lungs?

B. Alveolar pores

What is the opening between the vocal cords called?

A. Glottis

Which respiratory volume increases significantly in obstructive disorders like asthma?

A. Residual volume

What is the function of type I alveolar cells?

C. Form the thin wall for gas exchange

What part of the brain controls rhythmic breathing?

C. Medulla oblongata

Which structure allows equalization of pressure in the middle ear?

C. Pharyngotympanic tube

What happens to pH during hypoventilation?

B. Decreases (acidosis)

Why does gas exchange become impaired when respiratory membranes thicken?

B. Diffusion slows down

What causes the PO₂ to decrease from atmospheric air (160 mm Hg) to alveolar air (104 mm Hg)?

B. Humidification and mixing with residual air

What is cyanosis a sign of?

B. Hypoxia

How is most carbon dioxide transported in the blood?

D. As bicarbonate ions

What is the Bohr effect?

B. CO₂ and low pH promote O₂ release from hemoglobin

What role does hemoglobin play in oxygen transport?

C. Binds to oxygen for transport in red blood cells

What happens to hemoglobin’s affinity for oxygen as more O₂ binds?

C. It increases

What causes the oxygen-hemoglobin dissociation curve to shift right?

C. High CO₂, low pH, or increased temperature

Which factor most strongly stimulates breathing under normal conditions?

C. Increased carbon dioxide

What is the Haldane effect?

B. High O₂ promotes CO₂ release from hemoglobin

What is the most abundant gas in atmospheric air?

C. Nitrogen

What law explains why gases diffuse down their pressure gradients?

C. Dalton’s Law

What is minute ventilation?

C. Total air movement per minute (TV × respiratory rate)

What is the main driver for oxygen unloading at tissues?

C. Low PO₂ in tissues

Which of the following is most soluble in plasma?

C. Carbon dioxide

Which law explains why CO₂ dissolves more easily in blood than O₂?

B. Henry’s Law

Which of the following happens during quiet expiration?

D. Muscles relax and lungs recoil

What do chemoreceptors in the aortic and carotid bodies detect?

B. pH, CO₂, and O₂ levels in the blood

What is the main function of the respiratory membrane?

B. Allow gas exchange between air and blood

What is the effect of increasing respiratory rate on CO₂ levels?

B. Decreases CO₂ levels

Which muscle is most responsible for quiet inspiration?

C. Diaphragm

What happens when airway resistance increases?

C. Breathing becomes more difficult

Where is the respiratory control center located?

B. Pons and medulla

What structure divides the nasal cavity and helps direct airflow?

A. Septum

What causes alveolar collapse in premature infants?

C. Absence of surfactant

What is internal respiration?

B. Gas exchange between blood and tissue cells

What causes airflow into the lungs during inspiration?

B. Pressure in lungs drops below atmospheric pressure

What is tidal volume?

C. Air exchanged during normal breathing

What is the role of alveolar macrophages?

C. Clean debris and pathogens from alveoli

What increases during exercise to meet oxygen demands?

C. Respiratory rate and tidal volume

Why does high altitude trigger increased red blood cell production?

B. Decreased oxygen levels stimulate erythropoietin

How is most oxygen transported in the blood?

C. Bound to hemoglobin

Which gas has the greatest partial pressure in atmospheric air?

C. N₂

Which part of the lung receives its own bronchus, artery, and vein?

C. Bronchopulmonary segment

What is the primary site of resistance in the airway?

C. Bronchioles