Respiratory Tract and Alveoli - Anatomy and Physiology
- What supports the trachea, and why is it open posteriorly?
- C-shaped rings of hyaline cartilage. The open back, bridged by the trachealis muscle, lets the esophagus expand during swallowing.
- How many lobes does each lung have?
- The right lung has three lobes and the left lung has two; the left is smaller to make room for the heart (cardiac notch).
- Which airway marks the end of the conducting zone?
- The terminal bronchioles. The respiratory zone begins at the respiratory bronchioles, where alveoli first appear.
- What three things does the nasal cavity do to inhaled air?
- It warms, humidifies and filters the air, using its vascular mucosa, mucus and conchae.
- What do type II alveolar cells secrete?
- Surfactant. They can also divide to replace damaged type I cells.
- What is the function of type I alveolar cells?
- They form the thin squamous lining of the alveoli and make up most of the gas exchange surface.
- What type of epithelium lines the trachea and most bronchi?
- Pseudostratified ciliated columnar epithelium with goblet cells, which forms the mucociliary escalator.
- Which three layers make up the respiratory membrane?
- The alveolar epithelium, the fused basement membranes, and the capillary endothelium.
- What cells remove dust and microbes from the alveolar surface?
- Alveolar macrophages (dust cells), because the alveoli lack cilia and mucus.
- A child inhales a small bead into the lower airway. Into which main bronchus is it most likely to lodge?
- The right main bronchus, because it is wider, shorter and more vertical than the left.
- What prevents food from entering the larynx during swallowing?
- The epiglottis, which folds down over the laryngeal inlet as the larynx rises.
- What is the function of pulmonary surfactant?
- It lowers surface tension in the alveoli, preventing their collapse at the end of expiration and easing inflation.