9.1 Respiratory Anatomy

Notes

The respiratory system supplies oxygen and removes carbon dioxide. Air passes through the nasal cavity (warms, filters, humidifies), pharynx, larynx (voice box; the epiglottis covers it during swallowing), trachea (windpipe, held open by C-shaped cartilage rings), primary bronchi, smaller bronchioles, and ends in alveoli.

• The conducting zone moves air; the respiratory zone (respiratory bronchioles, alveoli) exchanges gas.
• Alveoli are tiny sacs of simple squamous epithelium wrapped in capillaries. Type II alveolar cells make surfactant, which reduces surface tension and prevents collapse. Premature infants may lack surfactant (respiratory distress syndrome).
• The lungs: right lung has 3 lobes, left lung has 2 (making room for the heart). Each lung is covered by visceral pleura; the pleural cavity holds a small amount of fluid.
• The trachea and bronchi are lined with ciliated epithelium and mucus that trap and sweep out particles.