Digestive and absorptive processes involve three parts namely the alimentary canal, the upper part of the small intestine and the lower portion of the large intestine. The three parts of the digestive tract constitute the whole digestive system. The human digestive system consists of two main divisions: the alimentary canal where the major functions of digestion take place and the intestines, which are the sites for absorption and passive loss of nutrients. There are three types of enzymes active in the human body. Enzymes are molecules that are responsible for changing food substances into simpler compounds that are ultimately used as nutrients in the body.
Two of the most important categories of enzymes are: complex and simple. The former are produced by the cells of the lower portion of the intestines, while the latter are synthesized by the liver, pancreas and other organs in the human digestive system. The cell-based digestive enzymes are mainly active in the alimentary canal, where they stimulate the production of bulk and fluid in the form of stool and juice.
One important enzyme is called pepsin. It is a pancreatic enzyme and it is found in the human digestive system and it aids in digestion by breaking down protein in the food that passes through it. Peptides are released during digestion and these combine with the fluid present in the gut to help break down and absorb nutrients present in the food. They are then absorbed into the bloodstream to help maintain health. Peptides are also excreted from the body in feces, urine and other forms of wastes.
The other important enzyme is cholecystokinin, produced by the liver and the pancreas and is important in digestion and absorption in humans. Its job is to break down the starch in the food that passes through the small intestine. The small intestine has three sections: the upper, middle and the lower intestines. The upper part contains the proteins that are not digested and are called pre-primed carbohydrates; the middle section is where all the carbohydrates in the food that is not broken down and absorbed are located; while the lower intestine contains the undigested proteins in the form of glucose. The undigested proteins are carried by the large intestine, and they are absorbed into the bloodstream through the large intestine.
The last enzyme is known as pepsin, which is produced by the kidneys and adrenal glands and it helps in absorption in human beings. It is also carried by the lymphatic vessels and flows into the blood stream through the colon, the large intestine and into the alimentary canal. The purpose of this is to neutralize the chemicals that are present in feces. The human body has four major systems for absorption: the oral cavity, the gastrointestinal tract, the pulmonary circulation and the skin.
The absorption process starts when there is a passage of food from the mouth towards the stomach. There are three types of the structures that are present in the alimentary canal and these are the upper, the lower and the terminal structures. These different structures have different functions in digestion. For example, the upper digestive tract has the highest rate of absorption. This happens because the gastric juices that are present in this area work against the gastric juices that are present in the lower digestive tract.
The upper alimentary canal is connected to the large intestine through the small and large vena cava. This structure is made up of the upper, the midline and the basal villi. The main function of the alimentary canal is to produce acids and enzymes that aid in breaking down the proteins found in the solid and semisolid foods that are consumed in the human diet. The role of the large intestine is to absorb the fat soluble vitamins and other nutrients.
The absorption process occurs when the acidic juices of the alimentary canal interact with the fats that are present in the digested food. This leads to the decomposition of the proteins, which are known as lipids. Once the material reaches the stomach, it is again broken down into simple substances known as peptides. Peptides are absorbed into the bloodstream and transported to all the body organs where they help in their respective function. The digestion and absorption process is very important in human beings and especially in children who have a deficiency in both the organs.