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What is correct about microvilli?
A. Also known as brush bordered epithelia
B. Found in small intestine and PCT both
C. Increase absorption of food
D. These are infoldings of cell membrane

Answer
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Hint: The cytoskeleton which forms the underline system to anchor cell membrane in the cytoplasm and provide a scaffolding protein. The cytoskeleton along with the cell membrane also extends to form certain organelles such as cilia, filopodia and microvilli. These extended organelles are present on the apical surface of the endothelial cells.

Complete step by step answer: The cytoskeleton often gives rise to acting based finger-like projections known as the microvilli. The microvilli are cellular membrane projections and are not infoldings. They are covered in plasma membranes and enclose cytoplasm. These are regarded as cellular extensions that extend outside to the plasma membrane.
Each microvillus contains a dense bundle of cross-linked filaments of actin. Actin filaments serve as the structural core of the microvillus. The actin filaments are cross linked by proteins such as fimbrin, villin and espin. The structural core of the microvillus is attached to the plasma membrane by lateral arms which are made up of myosin and calmodulin. Calmodulin is a calcium binding protein. The microvillus ends are referred to as plus end and minus end. The +end of the actin filament are located at the tip of the microvillus and are covered by capZ proteins. The minus ends are found anchored in the terminal web at the apical surface of the endothelial cells. The minus end is composed of a complicated set of proteins.
 Microvilli are found in the apical surfaces of the epithelial cells. They are found attached to the plasma membrane. THe microvilli are involved in a number of functions. The apical epithelia consist of several small villi and microvilli that appear to give a brush-like appearance to the border and is referred to as brush border epithelium.
The microvilli are found in the organs such as intestine, kidney and is also observed on the surfaces of the eggs. In the small intestine, the microvilli act to increase the surface area for absorption of food materials or nutrients. They increase the surface area for diffusion and reduce the increase in the volume.
Therefore, the correct option is option C.

Note: The microvillus are fine cell projections that are present in the plasma membrane. They are formed from the cytosol and the plasma membrane and project outside the body of the cells. THe microvilli acts to increase the surface areas of organs such as the small intestine to allow maximum absorption of nutrition.