Gastrin, a peptide hormone released by G-cells of the stomach, has many functions in digestion. It triggers parietal cells to release , it increases gastric motility, it triggers chief cells to secrete pepsinogen, and it stimulates the gallbladder to release bile. 

The intestinal brush border is the microvilli-covered surface of the small intestine. It is where a large part of the digestive process occurs, aided by brush-border enzymes such as sucrase, maltase, lactase, and carboxypeptidase. 

Insulin, while secreted by the pancreas, is not an enzyme. Rather it is a peptide hormone that plays a role in lipid and blood sugar metabolism.

The other enzymes listed are all pancreatic enzymes that play a role in digestion. Amylase breaks down carbohydrates, while lipase and sterol esterase break down fats. Carboxypeptidase is an enzyme that removes the final amino acid group from a protein.

 is secreted by parietal cells of the stomach. Chief and foveolar cells of the stomach secrete pepsinogen and mucus respectively, and M cells are not stomach cells, but rather intestinal cells involved in mucosa-associated lymphoid tissues, or MALT. 

The two main forms of digestion and chemical and mechanical. Mechanical digestion involves the physical crushing, mixing, and breaking down of food particles into small pieces or slurries. Mechanical digestion primarily occurs with mastication and is carried out to some degree by peristaltic contractions of the stomach and intestine. Chemical digestion is the further breakdown of food particles into their molecular parts. This is carried out primarily via enzymes, HCl, and bile.

Stomach transit time varies widely: it can take anywhere from ten minutes to four hours for food to pass through the pyloric sphincter into the duodenum. Transit time in the stomach is affected by the composition of the meal, and by the individual's rate of gastric emptying. Transit time may be shortened due to consumption of liquid or simple-carbohydrate foods, or lengthened in the case of consumption of solid food that has a high protein or fiber content.

Normal transit time of food through the small intestine is three to eight hours. This is significantly longer than transit time through the stomach due to the wider variety of digestive processes that occur in the small intestine, including the catabolism of proteins, lipids, nucleic acids, and simple and complex carbohydrates.

The average colon transit time for both adults and children is between 32 and 48 hours. This is significantly longer than the transit times of food through the stomach and small intestine, which averages 4-12 hours total. A slow transit time through the colon can be increased by various lifestyle factors such as exercise and hydration, and  dietary changes such as an increase in fiber-rich foods and avoidance of food allergies or other constipation triggers.

The main artery supplying blood to the small intestine is the superior mesenteric artery. This vessel branches off the abdominal aorta and supplies the lower part of the duodenum, the ileum, the jejunum, and two-thirds of the transverse colon. The rest of the colon and the rectum are supplied by the inferior mesenteric artery, while the right hepatic and left gastric supply the liver and stomach, respectively.

We have three main types of salivary glands: the parotid glands, the submandibular glands, and the sublingual glands. The thymus gland is not a salivary gland, and is located in the chest just superior to the heart.