Abattoir Practices and Animal Products Technology

INTESTINAL STRUCTURE

• There are five distinct layers of tissues, viz. the mucosa, the submucosa, the circular muscular layer, the longitudinal muscular layer and the serosa, from the inside to the outside in order of appearance.

• The mucosa surrounds the intestinal lumen.
  • It consists of the mucosal membrane, composed of epithelial cells, many of which are specialized into glands that perform various functions, including digestion, secretion and absorption.
  • Lymphatic tissues are also present near the basal portion of the mucosa in the form of nodules and there are a number of blood vessels and nerve plexuses.
• The next layer, the submucosa consists mainly of collagenous and elastic fibres.
  • This collagen-rich submucosa forms the main source for natural casings.
• The circular muscle layer contains smooth muscle cells, which are arranged with their longer axis around the digestive tube.
  • In hog this layer is thicker than the longitudinal layer.
• The longitudinal muscle layer has its cells oriented at right angles to those of the circular layer and has a relatively high content of collagen.
  • In living animals these two layers function in the peristaltic movement of the intestine.
• The fifth layer is the serosa, which is relatively thin as compared to the other four layers.
  • It is composed of collagen and elastic fibres with some connective tissue cells.
  • In hog intestine this layer is thinner than in cattle and much less tightly bound to the other layers.