Zones of the lung

The Zones of the Lung refer to the three distinct regions within the lung that are differentiated by the varying pressure and blood flow. These zones include the Zone 1, Zone 2, and Zone 3. Each zone has unique characteristics and functions that contribute to the overall function of the lung.

Zone 1

Zone 1 of the lung, also known as the non-dependent zone, is the uppermost region of the lung. It is characterized by high alveolar pressure and low pulmonary blood flow. This zone is typically only present under pathological conditions, such as severe hypotension or positive pressure ventilation.

Zone 2

Zone 2 is the middle region of the lung. It is characterized by intermittent blood flow, which is controlled by the difference between the arterial and venous pressures. The blood flow in this zone is determined by the difference between the pulmonary arterial pressure and the alveolar pressure.

Zone 3

Zone 3, also known as the dependent zone, is the lowermost region of the lung. It is characterized by continuous blood flow, which is due to the high pulmonary venous pressure that exceeds the alveolar pressure. This zone has the highest blood flow and is the most affected by gravity.

Clinical Significance

Understanding the zones of the lung is crucial in the clinical setting, particularly in the management of patients with respiratory diseases. For instance, in conditions such as pulmonary edema and pneumonia, the pathological changes often start in Zone 3 and progress upwards.

See Also

• Lung
• Pulmonary circulation
• Respiratory system

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