The microscopic folds that extend from the epithelium's apical surface to increase the area for absorption and secretion are called microvilli.
Microvilli are cellular membrane protrusions that improve diffusion surface area while minimizing volume increase than can be seen through a microscope. Plasma membrane covers microvilli, enclosing cytoplasm and microfilaments (the main structure is given by the actin filaments).
In the gastrointestinal system, microvilli serve as the major surface for nutrition absorption. The microvillar membrane is filled with enzymes that help in the breakdown of complicated nutrients into simpler molecules that are more easily absorbed because of its critical role.
Learn more about gastrointestinal absorption here: https://brainly.com/question/2729062
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