Microanatomy of the Digestive Tube Digestion Index Glossary Microanatomy of the Digestive Tube Remarkably diverse and specialized processes take place in different sections of the digestive tract, but there is a fundamental consistency in the architecture of the tubular digestive tract. From the mouth to the anus, the wall of the digestive tube is composed of four basic layers or tunics.
Tunica serosa is the outermost covering of the digestive tube.
In the abdominal cavity, the serosa on each side of the tube fuses together to form a suspensory structure called mesentery , which houses vascular and nervous supplies to the digestive tract and is continuous with the lining of the cavity. Tunica muscularis endows the digestive tube with an ability to be motile. In most of the digestive tube, this tunic consists of two thick layers of smooth muscle. Muscle fibers in the inner layer are aligned circularly, whereas those in the outer layer have a longitudinal orientation. This combination of circular and longitudinal smooth muscle gives the tube an ability to perform complex movements that squeeze and propel ingesta in the lumen.