The digestion process in a body begins a little before food particles goes in the body. Even before the intake of food, the aroma or sight of food causes salivation. The digestion process starts when the food goes in the mouth and the teeth start breaking the food component in small pieces. These pieces get mixed with saliva.
The tongue also assists in moving the food from back to front and makes a bolus in the form of a ball which will be pushed inside the mouth into the oesophagus.
Through the oesophagus, the food reaches the stomach which is the main organ for digestion process. In the stomach, gastric juices break food further. There are also muscle contracts which assist in this food breakage. These small particles of food remain in stomach for about 2 hours till they become a paste and then the digestion process continues by moving of this paste into small intestine.
In small intestine, this paste is further broken down and mixed with bile. From this intestine, many villi take the nutrients and carry them in blood to body cells bringing back any waste products back here. From here this gets transferred to large intestine where after digestion process is complete. The waste product is left after some processing and then wait for its turn to be excreted.
Extracellular digestion is a phenomenon associated with the saprobionts like annelids, crustaceans , chordates, lichins,arthropods and other vertebrates. The saprobionts feed by the process of extracellular digestion process and derive energy from growth and reproduction. The organisms secrete digestive enzymes through their cell membrane onto the food material. The food is contained in the digestive spaces and it broken down in molecules.
These food molecules are then absorbed by the phenomena of phogocytosis. This phenomena is referred to as extracellular digestion process since the digestion of the food substances occurs outside the cells. In the case of complex organisms , it occurs in the lumen of the alimentary canal and it is transported by blood and other body fluids. Intracellular digestion refers to the process that occurs inside the cell, while extracellular refers to the process of digestion that occurs outside the cell.
In the intracellular and extracellular digestion process the chemical breakdown of food matter ingested by the organism occurs wither inside or outside the cells. In the case of both intracellular and extracellular, the nutrients thus produced by the process are absorbed by the cells. Intracellular and extracellular process occurs in simple organisms and large complex organisms it provides energy that facilitates the normal body functions.
Extracellular phenomena is important for the large organisms that require a large amount of energy. The herbivore stomach has the following attributes. The stomach may be simple or having multiple chambers. The digestion process in stomach where acidity may range from pH 4 to 5 with food in the stomach.
In case of the stomach of herbivores, the capacity of the stomach will be less than thirty percent of the total volume of the digestive tract. The length of the small intestine will be ten or more than twelve times the body length. It has been found that the stomach of the herbivores cannot detoxify vitamin A. The kidneys produce moderately con citrated urine which is very unlike the carnivores digestion process that excrete highly concentrated urine.