Respiratory Epithelium and Alveolar Cells Quiz

Respiratory Epithelium and Alveolar Cells in the Respiratory System

• The nasal cavity epithelium is similar in cellular composition to the trachea and contains olfactory epithelium with specialized sensory cells.
• The respiratory epithelium in the trachea and bronchi consists of basal cells, columnar ciliated cells, goblet cells, brush cells, bronchial endocrine cells, club cells, and pulmonary ionocytes.
• Goblet cells, comprising approximately 30% of the cell population, produce mucin glycoproteins and increase in number during chronic irritation.
• Club cells, which protect the bronchiolar epithelium, secrete a surface-active agent that reduces surface tension and helps prevent collapse of bronchioles.
• Pulmonary ionocytes, regulating salt balance and making up about 1% of airway cells, contain high levels of CFTR, a chloride ion channel, and are involved in cystic fibrosis.
• Cystic fibrosis is caused by a mutation in CFTR, leading to defective ionocytes and loss of chloride conductance, resulting in thickened mucus.
• Airway smooth muscle, lining the airways of the lungs, contains GPCRs and is regulated by Ca2+, PKA, myosin light chain kinase, and myosin light chain phosphatase, affecting bronchial tone.
• Alveoli, the site of air-blood barrier and gas exchange, contain type I alveolar cells permitting gas exchange, type II alveolar cells producing surfactant, and brush cells serving as air quality sensors.
• Type II alveolar cells produce surfactant, an oily mixture of proteins and phospholipids, stored in lamellar bodies, and containing surfactant proteins A, B, C, and D.
• Pulmonary surfactant decreases alveolar surface tension, prevents alveolar collapse, and increases lung compliance, while surfactant proteins organize the surfactant layer and modulate alveolar immune response.
• Phospholipids and surfactant proteins are synthesized in the rough and smooth endoplasmic reticulum, transported to and stored in lamellar bodies, and involved in fusion with the cell membrane and reuptake for recycling.
• Alveolar type I and II cells communicate with each other, with type II cells producing surfactant and type I cells acting as stretch sensors using ATP for communication.