This sequestered tissue is therefore not connected to the normal bronchial airway architecture, and fails to function in, and contribute to, respiration of the organism.

The most frequently supported theory of sequestration formation involves an accessory lung bud that develops from the ventral aspect of the primitive foregut.

In contrast, later development of the accessory lung bud results in the extrapulmonary type that may give rise to communication with the GI tract.

The most common location is in the posterior basal segment, and nearly two thirds of pulmonary sequestrations appear in the left lung.

[citation needed] Bronchopulmonary sequestration (BPS) is a rare congenital malformation of the lower respiratory tract.

[citation needed] BPS is estimated to comprise one to six percent of all congenital pulmonary malformations, making it an extremely rare disorder.

Intralobar sequestration in which the lesion is located within a normal lobe and lacks its own visceral pleura.

The remaining 25% of sequestrations receive their blood flow from the subclavian, intercostal, pulmonary, pericardiophrenic, innominate, internal mammary, celiac, splenic, or renal arteries.

[citation needed] In a few instances, fetuses with sequestrations develop problematic fluid collections in the chest cavity.