Respiratory System; The respiratory epithelium consists of conducting pathways


The respiratory epithelium consists of conducting pathways

The respiratory epithelium consists of conducting pathways (nasal cavities, naso and oropharynx, larynx, trachea, bronchi, and bronchioles) and respiratory portions (respiratory bronchioles and alveoli). The nasal epithelium includes a region of specialized olfactory receptors.

All portions of the respiratory & respiratory epithelium

Ciliated cells appear in all portions of the respiratory system except the respiratory epithelium and move mucus and particulates toward the oropharynx (mucociliary escalator). Gas exchange in the lungs takes place across a minimal barrier consisting of the capillary endothelium, a joint basal lamina, and an exceedingly thin alveolar epithelium consisting primarily of type I pneumocytes. Type II pneumocytes are responsible for the secretion of surfactant, a primarily lipid substance that facilitates respiration by reducing alveolar surface tension. The type II pneumocyte is recognizable at the EM level by the presence lamellar bodies that contain surfactant comprised primarily of lecithin (Dipalmitoylphosphatidylcholine, DPPC) as well as some cholesterol and sphingomyelin.
Ciliated cells appear in all portions of the respiratory system except the respiratory epithelium and move mucus and particulates toward the oropharynx (mucociliary escalator). Gas exchange in the lungs takes place across a minimal barrier consisting of the capillary endothelium, a joint basal lamina, and an exceedingly thin alveolar epithelium consisting primarily of type I pneumocytes. Type II pneumocytes are responsible for the secretion of surfactant, a primarily lipid substance that facilitates respiration by reducing alveolar surface tension. The type II pneumocyte is recognizable at the EM level by the presence lamellar bodies that contain surfactant comprised primarily of lecithin (Dipalmitoylphosphatidylcholine, DPPC) as well as some cholesterol and sphingomyelin.

Respiratory distress syndrome (RDS)

Although surfactant is produced beginning at about the 28th week, premature babies born before 30 weeks are likely to suffer from respiratory distress syndrome (RDS) because of the absence of surfactant. There are a variety of treatments for RDS including the administration of artificial surfactant and ventilation for the premature infant. In cystic fibrosis, mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) result in defective Cl- transport and increased Na+ absorption. HCO3- transport through the CFTR is also defective. The result is thick, more viscous (less watery) mucus in the airways that promotes bacterial infections and reduces the effectiveness of the mucociliary escalator.

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