Cells of intestines

The epithelial layer of both small and large intestines contains many types of cells. Four of them are particularly important in maintaining functions of both intestines: absorptive cells, goblet cells, paneth cells, and enteroendocrine cells.

Absorptive cells are abundant in the epithelium of the small intestine. Their role is to release enzymes that digest food and absorb nutrients using microvilli. In the large intestine, absorptive cells are not so abundant but still present for absorption of water and residues of nutrients that were not absorbed in previous parts of the intestinal tract.

Goblet cells are found scattered among other cells in the epithelium of many organs, especially in the intestinal and respiratory tracts. Their main role is to secrete mucus. Secretion of mucus from goblet cells is caused by irritating stimuli like food matter traveling through the digestive tract. They are present in both small and large intestines. Their role is vital in the large intestine, where they transfer waste matter through the colon and protect the lining of the tract against bacteria and other microorganisms present in the large intestine.

In the crevices of the small intestinal mucosa, cells form the intestinal glands. Besides absorptive and goblet cells, intestinal glands also contain paneth cells and enteroendocrine cells. Paneth cells secrete bactericidal enzymes and are capable of phagocytosis. They provide host defense against unwanted microbes only in the small intestine since they could harm digestive microbes located in the large intestine. Enteroendocrine cells produce and release hormones in response to various stimuli. Each type of enteroendocrine cell secretes different hormones: S cells secrete secretin, CCK cells secrete cholecystokinin, and K cells secrete glucose-dependent insulinotropic peptide. These cells are not present in the large intestine, as their function is unnecessary.

Figure 1: Comparison of walls of the small and large intestine and four main types of cells inhabiting these organs. Depending on the function of the intestine, the types and amounts of cells are different.