Digestion, Absorption and Metabolism of Nutrients

AbstractThe physiology of digestion as well as the digestive system in larger animals is essentially similar for all monogastric and simple stomach animal. The group of digestive enzymes are secreted from stomach to the large intestine and act on the consumed foods for degradation into simpler forms for making the complex food for readily absorbable in the lower tract. The undigested foods and partially digested microbes will be eliminated through rectum as faeces. Organic components of foods are in the form of large insoluble molecule and foods are the mixture of different organic and inorganic nutrients which are very much necessary for running the proper physiological processes in the biological system. These important and common organic and inorganic nutrients are proteins, fats, carbohydrates, water, minerals and vitamins. These are very important and essential, without these nutrients it is very difficult to run the vital physiological system, therefore for running vital function regular intake is very much essential and for sustenance of the biological system. These nutrients are very complex in nature and having very big molecular weight and as such these nutrients are not absorbed from the digestive system and need some pre-utilization processing, i.e. broken down into smaller units before absorption through digestive system. Therefore, it is necessary to reduce the particle size of the nutrients into simpler and smaller forms for entering into portal blood after crossing the intestinal barrier easily. Very few of these nutrients that are very smaller in size can pass directly from the intestinal wall to the body tissue, however most of the nutrients need to be simplified into smaller size to pass the barrier and absorb through the intestinal wall. The larger food molecules must be broken down into simple compounds before they pass through the mucous membrane of the alimentary canal further enter into the blood and lymph. This breakdown process of foods to make the complex food material into smaller and simpler form in the digestive tract is termed as “digestion”; it includes all the activities in the alimentary tract and its associated glands. The processes such as mechanical, chemical and microbial are essential for digestion into simpler form. The passage of digested nutrients into smaller size from the lower digestive tract through the mucous membrane is termed as “absorption”. After absorption, the nutrients are utilized for maintenance as well as biosynthesis of the different molecules which are important for the biological system. The utilization of these vital nutrients for sustaining the life process by the animal body and the excretion of the end products produced during the utilization process of the nutrients in the body is termed as “metabolism”.