Your intestine is lined with individual cells. No fluids leak between these cells from the gut into your body. Why?

Because of the tight juntions that join the intertinal apithelial cells.

Explanation:

The intestinal epithelium is formed by epithelial cells sealed by tight junctions (cell-cell junction), this layer keeps the contents of the intestine inside it and at the same time, it regulates the permeability of nutrients through transcellular transport allowing to selectively transport molecules.

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