Great alveolar (type II) cells of the alveoli secrete a _______ that decreases the surface tension and prevent alveoli collapse when exhaling . Great alveolar (type II) cells of the alveoli secrete a _______ that decreases the surface tension and prevent alveoli collapse when exhaling . Solution Ans- pulmonary surfactant . Pulmonary surfactant Type II alveolar cells cover a small fraction of the alveolar surface area. Their function is of major importance in the secretion of Pulmonary surfactant which decreases the surface tension within the alveoli. They are also capable of cellular division, giving rise to more type I alveolar cells when the lung tissue is damaged. These cells are granular and roughly cuboidal. Type II alveolar cells are typically found at the blood-air barrier Although they only comprise 5% of the alveolar surface, they are relatively numerous (60% of alveolar epithelial cells) Development:- Type II cells start to develop at about 26 weeks of gestation, secreting small amounts of surfactant. However, adequate amounts of surfactant are not secreted until about 35 weeks of gestation - this is the main reason for increased rates of infant respiratory distress syndrome, which drastically reduces at ages above 35 weeks gestation. Functions- Type II cells are responsible for the production and secretion of pulmonary surfactant (the majority of which are dipalmitoyphosphatidylcholine), a group of phospholipids that reduce the alveolar surface tension. Surfactant phospholipids are stored in type II alveolar cells in lamellar bodies, which are specialized vesicles. Release of surfactant in lamellar bodies occurs from an infant\'s first breath onwards. Type II pneumocytes can replicate in the alveoli and will replicate to replace damaged type I cells. MUC1 a human gene associated with type II pneumocytes, has been identified as a marker in lung cancer.

1. Great alveolar (type II) cells of the alveoli secrete a _______ that decreases the surface tension
and prevent alveoli collapse when exhaling .
Great alveolar (type II) cells of the alveoli secrete a _______ that decreases the surface tension
and prevent alveoli collapse when exhaling .
Solution
Ans- pulmonary surfactant .
Pulmonary surfactant
Type II alveolar cells cover a small fraction of the alveolar surface area. Their function is of
major importance in the secretion of Pulmonary surfactant which decreases the surface tension
within the alveoli. They are also capable of cellular division, giving rise to more type I alveolar
cells when the lung tissue is damaged. These cells are granular and roughly cuboidal. Type II
alveolar cells are typically found at the blood-air barrier Although they only comprise 5% of the
alveolar surface, they are relatively numerous (60% of alveolar epithelial cells)
Development:-
Type II cells start to develop at about 26 weeks of gestation, secreting small amounts of
surfactant. However, adequate amounts of surfactant are not secreted until about 35 weeks of
gestation - this is the main reason for increased rates of infant respiratory distress syndrome,
which drastically reduces at ages above 35 weeks gestation.
Functions-
Type II cells are responsible for the production and secretion of pulmonary surfactant (the
majority of which are dipalmitoyphosphatidylcholine), a group of phospholipids that reduce the
alveolar surface tension. Surfactant phospholipids are stored in type II alveolar cells in lamellar
bodies, which are specialized vesicles. Release of surfactant in lamellar bodies occurs from an
infant's first breath onwards.
Type II pneumocytes can replicate in the alveoli and will replicate to replace damaged type I
cells.
MUC1 a human gene associated with type II pneumocytes, has been identified as a marker in
lung cancer