The layers of a natural casing can be seen in the cross-section from the outside to the inside. The outermost layer is the so-called gut fat, followed by the serosa, i.e. the epidermis, the submucosa, the muscle layers and finally the mucous membrane with the intestinal villi.
The outer fat is the layer of fat around the intestines, thus also around the intestines.
The serosa is a layer of skin that covers the intestine.
The submucosa is a coarse fibrous, vascular connective tissue sheath and the lower or inner part of the serosa.
The muscle layer is processed into the actual natural intestine. It consists of a longitudinal and transverse fibre layer.
The mucosa is composed of intestinal villi and intestinal glands and is removed during mucus.