Yasemin Saplakoglu in Quanta:
Breaking down food requires coordination across dozens of cell types and many tissues — from muscle cells and immune cells to blood and lymphatic vessels. Heading this effort is the gut’s very own network of nerve cells, known as the enteric nervous system, which weaves through the intestinal walls from the esophagus down to the rectum. This network can function nearly independently from the brain; indeed, its complexity has earned it the nickname “the second brain.” And just like the brain, it’s made up of two kinds of nervous system cells: neurons and glia.
More here.