The term "intestinal lining" refers to the inner surface or mucosa of the small and large intestines. It is composed of several layers of specialized cells that work together to absorb nutrients, water, and electrolytes from the food we eat while also providing a barrier against harmful substances entering our bloodstream. The lining is made up of simple columnar epithelial cells in the small intestine and goblet cells in the large intestine that secrete mucus to lubricate the passage of feces.