·         Animals that ingest bulk food unavoidably take in some matter that they are incapable of using in the case of unicellular organisms that form food vacuoles, the vacuoles eventually fuse with the cell membrane and then rupture releasing indigestible wastes to the outside. Substances that cannot be digested such as cellulose pass into the colon or large intestine.

·         Most animals including humans feed by a process called holozoic nutrition. This means that the animal has a gut tube(alimentary canal) that runs through its body and the animal has  mouth at one end (this is where the food goes in), an anus at the other end where undigested food ( faeces) passes out.


Egestion is the act of excreting unusable or undigested material from a cell as in the case of single celled organisms or from the digestive tract of multicellular animals. After the process of digestion and absorption, large amount of material remain undigested. These material largely consisting of plant fibres, dead bacteria etc are passed into the rectum and are eventually thrown out of the body through the anus. The undigested waste matter is called faeces. The brown colour of faeces is due to the presence of bile pigments.

Egestion is the act of voiding or discharging undigested food or faeces from the lower portion of intestine. We can say that egestion is the process of elimination of undigested food material through anus.

Process of Egestion:

·         After the ingestion, the food is digested and the nutrients are absorbed through the GI tract. After the processes, the remaining waste should be removed from the body. The removal of this waste from the body is egestion. In most multicellular organisms, the egestion takes place through the anus, whereas in unicellular organism it takes place via cell membrane.

·         Egestion is simply passing out undigested food from the end of the large intestine. If we egested out then our body is like a tube, then the stuff that comes out of the large intestine has never actually been inside your cells. It is mostly cellulose and other plant fibres that went into the mouth a day or day ago, have not been digested nor absorbed and so come out of the other end.

Some important points about Egestion:

·         Egestion should not be confused with excretion in which the waste materials are produced by metabolic activity in the body’s tissues.

·         Excess water is absorbed back into the body in the large intestine, what is left is undigested food. This is stored in rectum, the lower part of large intestine. It then comes out of the rectum through the anus as faeces.

·         The digestive contains many bacteria in the digestive system are important for the process of digestion. For example:  

·         These bacteria can digest some substances that humans cannot digest such as certain carbohydrates like cellulose.

·         They can reduce the chance of harmful bacteria multiplying and causing disease.

·         They can produce some vitamins that humans need such as vitamin B and K.


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