ABSTRACT
The digestive system is composed of a series of tubular organs and accessory glands that have important functions in the digestion process. There are common structures on all the hollow organs of the digestive tract, with four layers from the lumen: mucosa, submucosa, muscularis, and serosa/adventitia. These layers have different features in the different parts of the tract, starting from the oral cavity and followed by the pharynx, oesophagus, stomach, small intestine (duodenum, jejunum, and ileum), and large intestine (caecum, colon, rectum, and anus). The main glands associated with the digestive system are the salivary glands, producing saliva; pancreas, producing pancreatic juices (exocrine) and hormones (endocrine); the gall bladder; and liver.
