Processes of Animal Nutrition

Nutrition involve four steps

Ingestion : Process of intake of food materials.

Digestion : The conversion of large, complex, insoluble molecules of nutrients into small, simple and soluble form.

Extracellular : Digested outside the cell i.e., in gut or GVC. (Gastro Vascular Cavity)

Intracellular : Digested within the cell. e.g., protozoans, sponges.

Assimilation : Converting absorbed food materials into the cellular components for their utilization.

Egestion : The removal of undigested and unabsorbed part of food (waste) from the body. In Hydra both extracellular and intracelluar digestion takes place.

Digestive System of Vertebrates

In vertebrates digestion is performed by alimentary canal which divides on the basis of function. The major parts are: mouth, pharynx, oesophagus, stomach, small intestine, large intestine and anus (or cloaca).

It is longer in herbivores than carnivores.

The major accessory glands associated with it are salivary glands, liver and pancreas.