how are alveoli designed and why
Answers
Answer :-
Alveoli are designed in the shape balloon/sac like structures, forming the terminals of the "Bronchioles".
Such a structure of the alveoli provides a large surface area (like villi in intestine) for gaseous exchange through diffusion.
Extra Information :-
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☆ The wall of alveoli consists of 2 types of alveolar epithelial tissues :-
- Type I alveolar cells
- Type II alveolar cells
☆ Type I alveolar cells are predominant squamous epithelial cells.
☆ Type I alveolar cells are more in number.
☆ Type II alveolar cells are large and are scattered among the squamous cells.
☆ Type II alveolar cells are fewer in number.
☆ Type II alveolar cells produce "Surfactant", an oily secretion containing the mixture of "Phospholipids" and "Protiens".
☆ Type II alveolar cells are also known as "Septal cells.
☆ The alveolar wall possesses "Alveolar Macrophages" (dust cells).
☆ The alveolar wall possesses wandering "Phagocytes", ingesting fine dust particles and other debris.
☆ The number of alveoli in and average adult human being is estimated to be approximately around "300 million".
☆ In an average adult human being, the alveoli are estimated to expose a surface area of about "70 sq.metres".