Respiratory system Knowledge-Based Practice

Questions

1. 1.

   Which of the following factors causes a rightward shift in the hemoglobin-oxygen dissociation curve, thereby promoting the unloading of oxygen in systemic tissues?

   • A) An increase in blood pH
   • B) A decrease in carbon dioxide partial pressure
   • C) A reduction in local tissue temperature
   • D) An increase in hydrogen ion concentration
2. 2.

   In a healthy human at rest, which of the following changes serves as the primary chemical stimulus to increase the rate and depth of ventilation?

   • A) A moderate decrease in arterial oxygen partial pressure
   • B) An increase in the pH of arterial blood
   • C) An increase in arterial carbon dioxide partial pressure
   • D) An increase in blood plasma bicarbonate concentration
3. 3.

   What is the primary physiological function of pulmonary surfactant produced by type II alveolar cells?

   • A) Lowering surface tension at the air-liquid interface of alveoli to prevent their collapse during expiration
   • B) Binding and chemically transporting dissolved oxygen molecules across the alveolar-capillary membrane
   • C) Stimulating bronchiolar smooth muscle contraction to regulate airway resistance during ventilation
   • D) Neutralizing inhaled microorganisms through enzymatic degradation of bacterial cell walls
4. 4.

   In the human body, what is the primary chemical form in which carbon dioxide produced by cellular metabolism is transported through the bloodstream to the lungs?

   • A) Dissolved directly in blood plasma as molecular gas
   • B) Bound directly to the iron cations of heme groups in hemoglobin
   • C) Converted into urea within platelets for stable aqueous transport
   • D) Converted into bicarbonate ions within erythrocytes and dissolved in plasma
5. 5.

   During normal resting inhalation in humans, which of the following mechanical events occurs to draw air into the lungs?

   • A) Relaxation of the diaphragm and contraction of internal intercostal muscles, which decreases thoracic cavity volume and lowers intrapulmonary pressure.
   • B) Relaxation of the diaphragm and external intercostal muscles, which increases thoracic cavity volume and raises alveolar pressure above atmospheric pressure.
   • C) Contraction of the diaphragm and external intercostal muscles, which increases thoracic cavity volume and decreases intrapulmonary pressure below atmospheric pressure.
   • D) Contraction of the diaphragm and internal intercostal muscles, which decreases thoracic cavity volume and forces air into the respiratory tract.

Answers and step-by-step solutions appear after you finish the test.