*Multiple-choice questions (MCQs) on the lungs:* 1. Which of the following is the primary muscle of respiration? a) Intercostal muscles b) Diaphragm c) Abdominal muscles d) Sternocleidomastoid Answer: b) *Diaphragm* 2. What is the normal respiratory rate for a healthy adult at rest? a) 8-12 breaths per minute b) 12-20 breaths per minute c) 20-30 breaths per minute d) 30-40 breaths per minute Answer: b) *12-20 breaths per minute* 3. The exchange of oxygen and carbon dioxide in the lungs occurs in which structure? a) Bronchi b) Bronchioles c) Alveoli d) Pleura Answer: c) *Alveoli* 4. Which part of the brain primarily controls respiration? a) Cerebellum b) Medulla oblongata c) Thalamus d) Hypothalamus Answer: b) *Medulla oblongata* 5. What is the function of surfactant in the lungs? a) Increase lung compliance b) Decrease alveolar surface tension c) Facilitate oxygen diffusion d) All of the above Answer: d) *All of the above* 6. Which gas stimulates the respiratory center to regulate breathing? a) Oxygen b) Carbon dioxide c) Nitrogen d) Helium Answer: b) *Carbon dioxide* 7. What is the term for the volume of air that remains in the lungs after maximum exhalation? a) Tidal volume b) Inspiratory reserve volume c) Residual volume d) Vital capacity Answer: c) *Residual volume* 8. Which lung is slightly smaller to accommodate the heart? a) Right lung b) Left lung c) Both lungs are equal d) It varies from person to person Answer: b) *Left lung* 9. What type of epithelium lines the alveoli? a) Stratified squamous epithelium b) Pseudostratified columnar epithelium c) Simple squamous epithelium d) Cuboidal epithelium Answer: c) *Simple squamous epithelium* 10. Which structure prevents food from entering the trachea during swallowing? a) Epiglottis b) Uvula c) Soft palate d) Vocal cords Answer: a) *Epiglottis* 11. What is the term for difficulty breathing? a) Apnea b) Tachypnea c) Dyspnea d) Hyperpnea Answer: c) *Dyspnea* 12. Which disease is characterized by the destruction of alveolar walls leading to decreased gas exchange? a) Asthma b) Chronic bronchitis c) Emphysema d) Pneumonia Answer: c) *Emphysema*