Anatomy & Physiology
A practical map of the body's structures and systems
Lesson 16 of 20
Respiratory system
The respiratory system moves air and enables gas exchange between the atmosphere and blood. Ventilation moves air into and out of the lungs; diffusion transfers oxygen and carbon dioxide across thin exchange surfaces. Breathing mechanics involve pressure changes and the respiratory muscles. The system also contributes to sound production and acid-base balance.
Key points
- The upper airway filters, warms, and humidifies incoming air.
- The trachea branches into bronchi, then smaller airways that lead toward alveoli.
- Alveoli provide a large surface for gas exchange with pulmonary capillaries.
- The diaphragm contracts and descends during quiet inhalation, increasing thoracic volume.
- Most oxygen travels bound to hemoglobin; carbon dioxide is transported in several forms.
Key terms
- Ventilation
- Movement of air into and out of the lungs.
- Alveolus
- Microscopic air sac where gas exchange occurs.
- Diaphragm
- Primary muscle of quiet inspiration separating thoracic and abdominal cavities.
- Diffusion
- Net movement of particles from higher to lower concentration.
- Bronchiole
- Small airway branching from a bronchus toward alveolar regions.
Memory tip
Ventilation moves air; gas exchange moves molecules across membranes.
Clinical note
Comfortable positioning can support breathing; never restrict the client's ability to breathe freely.
Unit checkpoint
Lock it in: match the terms, then test yourself.