Light micrograph of the permanent folds of the human jejunum referred to as plica circulares. These folds support the intestinal mucosa where the surface epithelium forms very many finger-like protrusions termed villi. The chief functions of the epithelium are to absorb nutrients and to provide a protective barrier against toxins and harmful microorganisms. The core of each plica is the submucosa of connective tissues with blood vessels, lymphatics and enteric nerves. Paraffin section, haematoxylin and eosin stain. Magnification: x15 when printed at 10cm wide.