This topic covers the structure and function of the respiratory system, including the lungs, airways, alveoli, and the process of respiration.
Anatomy & Physiology of the Respiratory System
(Designed for quick review and deeper study)
| Region | Main Structures | Key Features |
|---|---|---|
| Upper Airway | Nasal cavity, paranasal sinuses, pharynx (nasopharynx, oropharynx, laryngopharynx) | • Warm, humidify, filter air • Ciliated epithelium + mucus trap particles |
| Lower Airway | Larynx, trachea, bronchi, bronchioles | • Rigid cartilaginous support (trachea, main bronchi) • Smooth‑muscle–rich bronchioles allow regulation of airflow |
| Lung Parenchyma | Alveolar ducts, alveolar sacs, alveoli | • Thin (type I) epithelial cells for diffusion • Type II cells secrete surfactant (reduces surface tension) |
| Pleural Cavities | Visceral pleura (covers lung), parietal pleura (lines thoracic wall), pleural fluid | • Creates a low‑friction, sealed environment • Negative intrapleural pressure keeps lungs expanded |
| Respiratory Muscles | Diaphragm, external intercostals, internal intercostals, accessory muscles (scalene, sternocleidomastoid) | • Diaphragm contraction → ↓ intrapleural pressure → inhalation • Expiration is usually passive (elastic recoil) |
| Component | Cell Types | Function |
|---|---|---|
| Respiratory epithelium (airways) | Ciliated pseudostratified columnar, goblet cells, basal cells | Mucociliary clearance; mucus production |
| Alveolar epithelium | Type I pneumocytes (flat, for diffusion), Type II pneumocytes (surfactant) | Gas exchange surface; surfactant synthesis |
| Pulmonary capillaries | Endothelial cells, pericytes | Tight barrier for diffusion; site of O₂/CO₂ exchange |
| Resident immune cells | Alveolar macrophages, dendritic cells | Phagocytosis of inhaled particles, antigen presentation |
Inhalation (Inspiration)
Exhalation (Expiration)
Ventilation Parameters