terminal saccular period

terminal saccular period

the period or phase of prenatal lung development lasting, in different parts of the lungs, from the twenty-sixth week or later until near term and followed by the alveolar period. Walls of the air spaces become thinner and the spaces divide into alveolar saccules with adjacent capillaries; type I and type II alveolar cells begin functioning, and surfactant is secreted. Also called terminal saccular phase.

ter·mi·nal sac stage of lung de·vel·op·ment

(tĕr'mi-năl sak stāj lŭng dĕ-vel'ŏp-mĕnt)
The period (26 weeks' gestation to birth) when many terminal sacs develop; their epithelium is very thin and capillaries bridge into the epithelial lining of the saccules, permitting adequate gas exchange for survival of the fetus if it is born prematurely.
Synonym(s): terminal saccular period.
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