Histology of the Gut

Whatever part of the gut you look at, from the oesophagus down to the rectum, the wall is built from the same four concentric layers, and this shared plan is what lets the canal move, protect and regulate itself along its whole length. The outermost layer, the serosa (or visceral peritoneum), is a thin sheet of squamous epithelium with some connective tissue that anchors the gut within the abdominal cavity. Beneath it lies the muscularis, made of smooth circular and longitudinal muscle fibres threaded through with a network of nerve cells and parasympathetic nerve fibres — this is the layer whose coordinated contractions produce peristalsis, the wave-like movement that pushes food along. Next comes the sub-mucosa, a layer of loose connective tissue carrying nerves and blood and lymph vessels, along with the sympathetic nerve fibres that regulate how much intestinal juice is secreted. The innermost layer, lining the lumen itself, is the mucosa — the layer that actu …