BCR TBL 12 - Airway Structure & Function, Ventilation and Lung Cell Biology

What is the function of pulmonary surfactant?

It reduces alveolar surface tension and prevents alveolar collapse.

What law explains the relationship between pressure, surface tension, and alveolar radius?

Law of Laplace (P = 2T/r).

Which alveolar cells produce surfactant?

Type II pneumocytes.

What condition is caused by insufficient surfactant in newborns?

Neonatal respiratory distress syndrome (NRDS).

How does surfactant influence lung compliance?

It increases lung compliance.

What happens to alveoli without surfactant?

They collapse, especially smaller ones.

What is the shape of the oxygen dissociation curve?

Sigmoidal.

What does a rightward shift of the oxygen dissociation curve indicate?

Decreased hemoglobin affinity for oxygen.

Name one factor that shifts the oxygen dissociation curve to the right.

Increased CO2, decreased pH, increased temperature, or increased 2,3-BPG.

What is the Bohr effect?

CO2 and H+ decrease hemoglobin’s oxygen affinity to enhance oxygen unloading.

What is the Haldane effect?

Oxygenation of hemoglobin promotes CO2 release.

What shifts the oxygen dissociation curve to the left?

Decreased CO2, increased pH, decreased temperature.

How is most oxygen transported in the blood?

Bound to hemoglobin.

What is the primary form of CO2 transport in blood?

As bicarbonate (HCO3−).

What enzyme catalyzes CO2 to HCO3− conversion in red blood cells?

Carbonic anhydrase.

What are goblet cells responsible for?

Producing mucus in the airways.

What type of epithelium lines the trachea?

Pseudostratified columnar ciliated epithelium.

Which airway cells have cilia to help move mucus?

Ciliated epithelial cells.

What do Clara (club) cells secrete?

Surfactant-like secretions and detoxifying enzymes.

What is the role of alveolar macrophages?

Remove debris and pathogens from alveoli.

Where are Type I pneumocytes found and what is their role?

Alveoli; gas exchange.

Which type of pneumocyte is more abundant?

Type I pneumocyte.

What is the conducting zone of the respiratory system?

Trachea to terminal bronchioles; no gas exchange occurs here.

Where does gas exchange begin in the respiratory tract?

Respiratory bronchioles.

What structures make up the respiratory zone?

Respiratory bronchioles, alveolar ducts, alveoli.

What separates the conducting and respiratory zones?

Terminal bronchioles.

How does the mucosal structure differ between bronchi and alveoli?

Bronchi have pseudostratified epithelium and goblet cells; alveoli have thin squamous epithelium.

What muscle is the primary driver of inspiration?

Diaphragm.

How does the diaphragm change during inspiration?

It contracts and flattens.

What muscles assist with forced expiration?

Internal intercostals and abdominal muscles.

What does passive expiration rely on?

Elastic recoil of the lungs.

What neural structure controls rhythmic breathing?

Medulla oblongata.

What does the Hering-Breuer reflex do?

Prevents overinflation of the lungs.

What is the role of external intercostal muscles?

Assist in lifting ribs during inspiration.

What is anatomical dead space?

Air in conducting airways not involved in gas exchange.

What is alveolar dead space?

Air in non-perfused alveoli.

What increases physiological dead space?

Pulmonary embolism or under-perfused alveoli.

What is a normal ventilation-perfusion (V/Q) ratio?

Approximately 0.8.

Where in the lung is the V/Q ratio highest in upright posture?

Apex.

What does Fick's Law state?

Gas diffusion is proportional to surface area and pressure gradient, and inversely to membrane thickness.

Which disease decreases alveolar surface area?

Emphysema.

Which disease increases alveolar membrane thickness?

Pulmonary fibrosis.

How does pulmonary edema affect gas exchange?

Increases diffusion distance, reducing efficiency.

What detects changes in CO2 and pH in blood?

Chemoreceptors.

What nervous system mediates bronchoconstriction?

Parasympathetic (via acetylcholine).

Which receptor type causes bronchodilation?

β2-adrenergic receptors.

What is the function of surfactant proteins B and C?

They reduce surface tension in alveoli.

What is the function of surfactant proteins A and D?

Host defense and immune function.

What structure connects adjacent alveoli?

Pores of Kohn.

What does an increase in 2,3-BPG do?

Decreases hemoglobin’s oxygen affinity (rightward shift).

What is residual volume?

Air remaining in lungs after maximal exhalation.

What is tidal volume?

Normal volume of air displaced between normal inhalation and exhalation.

What is the main role of alveolar capillaries?

Gas exchange between air and blood.

How is CO2 primarily buffered in the blood?

Converted to bicarbonate (HCO3−).

What stimulates erythropoietin (EPO) production?

Hypoxia.

How does high altitude affect oxygen transport?

Leads to increased ventilation, EPO production, and 2,3-BPG.

What is the respiratory exchange ratio (RER)?

Ratio of CO2 produced to O2 consumed.

What is lung compliance?

The ease with which the lungs expand.

How does surfactant affect compliance?

It increases compliance by reducing surface tension.

What happens to compliance in fibrosis?

It decreases.

What happens to compliance in emphysema?

It increases.

How is oxygen transported in plasma?

Small percentage is dissolved; most is bound to hemoglobin.

What is Dalton’s Law?

Total pressure is the sum of partial pressures of gases.

What is Henry’s Law?

Gas solubility is proportional to partial pressure.

What is Boyle’s Law?

Pressure is inversely proportional to volume.

Which lung volume increases with emphysema?

Residual volume.

Which gas is most soluble in blood?

Carbon dioxide.

What type of ventilation increases pH?

Hyperventilation.

What is the result of hypoventilation?

Respiratory acidosis (CO2 retention).

What causes respiratory alkalosis?

Excessive ventilation (loss of CO2).

What region of the lung has the greatest blood flow?

Base.

What maintains negative intrapleural pressure?

Opposing forces between lung recoil and chest wall expansion.

What is the primary site for airway resistance?

Bronchioles.

What does increased airway resistance cause?

Decreased airflow.

How do sympathetic nerves affect airways?

Cause bronchodilation.

What causes leftward shift of the oxygen dissociation curve?

Alkalosis, low CO2, hypothermia.

What happens to V/Q ratio in a pulmonary embolism?

It increases (ventilated but not perfused).

What type of cells clear debris in alveoli?

Alveolar macrophages.

Where are goblet cells not found?

Alveoli.

What is minute ventilation?

Tidal volume × respiratory rate.

How is alveolar ventilation calculated?

(Tidal volume − dead space) × respiratory rate.

What causes decreased V/Q ratio?

Airway obstruction or poor ventilation.

What happens in a rightward O₂ curve shift?

More O₂ is unloaded to tissues.

What is forced vital capacity (FVC)?

Maximal volume exhaled after full inspiration.

What causes increased 2,3-BPG?

Chronic hypoxia, anemia, high altitude.

What is an effect of CO poisoning?

CO binds hemoglobin more tightly than O₂, reducing O₂ transport.

What reflex controls inflation limits of lungs?

Hering-Breuer inflation reflex.

Which zone has cartilage support?

Conducting zone.

What effect does parasympathetic stimulation have on the lungs?

Increases mucus secretion, bronchoconstriction.

What is the function of the nasal cavity?

Filter, warm, and humidify inspired air.

What causes cough reflex?

Irritation of respiratory mucosa or foreign particles.

Which layer in bronchi contains blood vessels and glands?

Submucosa.

What is the main respiratory muscle?

Diaphragm.

What causes the pleural layers to adhere?

Surface tension of pleural fluid.

What causes increased physiological dead space?

Pulmonary embolism.

Which condition impairs gas diffusion?

Pulmonary edema, fibrosis.

Where are central chemoreceptors located?

Medulla oblongata.

What do central chemoreceptors respond to?

Increased CO₂ via changes in H+ in cerebrospinal fluid.

What do peripheral chemoreceptors detect?

Low O₂, high CO₂, low pH.

Where are peripheral chemoreceptors found?

Carotid and aortic bodies.