There are two types of alveolar cells. The type I alveolar cells which lines the alveoli and much more abundant than type II alveolar cells. Then the type II alveolar cells lesser in number but functions differently than type I alveolar cells. Type II alveolar cells secrete surfactant (composed of lecitin and sphingomyelin) for the lungs. Surfactant reduces the surface tension inside the alveoli, preventing alveolar consolidation. This is important as babies with dysfunctional type II alveolar cells (usually preterm babies less than 32 weeks age of gestation) will have respiratory distress syndrome in the absence of surfactant.
It has to be a, b or d then.
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Answer:
Tremendous heat and pressure within the earth cause the hot magma to flow in convection currents. These currents cause the movement of the tectonic plates that make up the earth's crust.
Explanation:
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Circulatory system because, movement causes circulation and movement is only possible by our muscles.
Here's some tips that should help: All cells, both prokaryotic and eukaryotic, have genetic information in the form of DNA. They also have ribosomes that translate genetic information into proteins. All cells also have a cell membrane that protects the contents of the cells. Inside the membrane, all cells have a gel-like substance known as the cytoplasm.