| Organization of lungs |
The conducting zone contains the trachea, the bronchi, the bronchioles, and the terminal bronchioles
The respiratory zone contains the respiratory bronchioles, the alveolar ducts, and the alveoli.
The conducting zone and the respiratory zone (but not the alveoli) are made up of airways.
The conducting zone has no gas exchange with the blood, and is reinforced with cartilage and smooth muscle, which are very strong. Smooth muscle has variable resistance to air flow. The conducting zone warms the air to 37 degrees C and humidifies the air. It also cleanses the air by removing particles.
The respiratory zone is the site of gas exchange with blood.
The smooth muscle tone in bronchioles, and therefore bronchiolar diameter, is controlled by:
- the sympathetic nervous system via noradrenaline acting on the beta receptors and causes bronchodilation
- the parasympathetic nervous system via acetyl choline which acts on the muscarinic receptors and causes bronchoconstriction
- many other non autonomic nervous and biochemical stimuli including, for example, carbon dioxide.
The intrapleural space is the potential space between the pleura lining the inner wall of the thoracic cage and the pleura lining the lungs.
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