Human Digestive System

• The process of digestion begins from the mouth itself and gets completed in small intestine.
• Stomach plays a key role in the digestion of food. It has gastric glands which secrete gastric juices needed to break down food to simple nutrients and thereby contributing to digestion.
• There are different hormones in our body that has different functions. For example, there could be pH changes associated with different types of food. This pH change stimulates the secretion of a hormone called gastrin which induces the production of digestive juices. But it is not directly connected to the digestion process.
• Water is present in cell, organs and tissues to help regulating temperature and maintaining body functions.
• Absorbed food enters the blood stream and is taken to different parts of the body.

Digestion is completed in the Ileum because it is the last part of small intestine where all the digestive secretions end. From the large intestine, the process of absorption occurs predominantly.

Enterokinase is an enzyme secreted by the intestinal mucosa that activates trypsinogen into its active form, trypsin.

Microvilli are small projections on the surface of epithelial cells in the small intestine that significantly increase the surface area for nutrient absorption.

Cattle are ruminants that possess specialized bacteria in their rumen capable of breaking down cellulose, which humans lack.

The saliva contains an enzyme called salivary amylase which hydrolyses starch into maltose. The complete digestion of starch occurs only in the small intestine by the action of pancreatic amylase. The activity of enzymes is strongly affected by several factors, such as temperature and pH.

Parietal cells secrete hydrochloric acid (HCl), which is necessary to convert pepsinogen into active pepsin. Without HCl, protein digestion in the stomach is severely impaired.

Succus entericus (intestinal juice) contains disaccharidases, dipeptidases, and lipases, but nucleases are primarily secreted by the pancreas.

Cellulose falls into the category of indigestible carbohydrates known as dietary fibre. Humans don't have an enzyme to digest cellulose. 

• The digestion process depends upon hydrolysis to provide the biochemical reactions that break down food.
•  The digestive tract secretes enzymes, such as proteases, carbohydrases, nucleases and lipases that, along with water, catalyze the hydrolysis that releases various nutrients. Hence, the Digestion of food occurs as a result of hydrolysis.

Enteropeptidase is an enzyme produced by the cells of the duodenum and is involved in the digestion in humans and other animals. Enteropeptidase converts trypsinogen (a zymogen) into its active form trypsin, resulting in the subsequent activation of pancreatic digestive enzymes

The digestive system plays an important role in the absorption of nutrients into the body. It takes the food we ingest, breaks it down mechanically and chemically in the mouth and stomach. It then absorbs nutrients, fats, proteins, and water in the intestines before eliminating the waste through the rectum

1. The stomach produces gastrin, hydrochloric acid and pepsinogen.
2. G-cells in the stomach releases gastrin in response to distension of the antrum. This, in turn, causes an increase in the secretion of HCl from the parietal cells or oxyntic cells, which kills or inhibits bacteria and provides the acidic pH for the proteases to work and pepsinogen is released from chief cells in the stomach called zymogenic cells or peptic cells. 
3. Pepsinogen, inactive form of the enzyme in presence of hydrochloric acid activates into the active form, pepsin. Pepsin breaks down proteins into polypeptides. Hence, sodium hydrogen carbonate is not produced in the stomach.