What is Egestion?

The egestion It is the process of discharge or expulsion of undigested materials, or food, by the body in the form of feces. In unicellular organisms, the materials are simply expelled by the cell whereas in multicellular organisms the food follows the path of the digestive system until it is expelled by the anus..

Egestion should not be confused with excretion, defined as a process of elimination of toxic materials, excess substances, or residues from the body..

E processanimal management

The human digestive system is responsible for processing food. This apparatus is mainly composed of the gastrointestinal tract, also known as the digestive tract, and a series of accessory organs, such as the pancreas, which also assist the digestive tract..

The process begins when food enters the gastrointestinal tract through the mouth. This first step is known as ingestion..

The food is then broken down through digestion. Mechanical breakdown starts in the mouth with the teeth and chemistry is aided by enzymes in the saliva and tongue that break down the food..

Food digested in the mouth is known as a bolus. The now food bolus travels through the esophagus to the stomach and then to the small intestine for further digestion..

Then, the digested food is absorbed through the walls of the small intestine into the blood, and thus, each absorbed particle travels to the places in the body where it is required..

Only small, soluble substances can pass through the walls of the intestine. The end products of digestion are glucose, fatty acids, glycerol, and amino acids. Minerals and vitamins do not need to be digested, so they are absorbed directly into the blood.

At the end of the journey through the small intestine, the nutrients have already been absorbed from the watery flow. The remaining substances, such as indigestible food, are transferred to the large intestine.

Start of egestion

Egestion takes place in the large intestine. The intestine is responsible for absorbing the water linked with indigestible substances, this material being the waste that becomes feces.

Stool is made up mainly of cellulose, bacteria, water, and fiber. This last component cannot be digested by humans, and is part of the cell wall of plants. Stool not only contains waste, it can also contain material toxic to the body.

Egestion begins when the waste is transferred and accumulated in the rectum until a stimulus is obtained from the body to evacuate the waste through the anus. Stools are broken down by bacteria in the large intestine, and are generally solid or semi-solid in consistency..  

Egestion is controlled by the anal sphincter, composed of the internal and external sphincters⁶. The internal sphincter is the continuation of the internal rectus muscle. This sphincter has non-voluntary control.

The external sphincter possesses a somatic innervation, or voluntary activity. When the anal canal is empty, the anal sphincter contracts. On the contrary, when the waste is accumulated in the rectum, the anal sphincter stretches, thus allowing the expulsion of stool..

References

1. Biology dictionary (2008). Egestion
2. Lucy, A. (2017). Differences between excretion and egestion. My Tutor LTD U.K.
3. Science Learning Organization (2011). The human digestive system.
4. BBC Life (2014). Diet, drugs and health. Revision Bites KS3.
5. Saint Charles College (2014). The digestive system.
6. Chawla, J. (2017). Anal Sphincter Electromyography and Sphincter Function Profiles. " Background, Indications, Contraindications. MedScape.
7. Keeton, W., and Harvey, D. (2016). Human digestive system. Encyclopedia Britannica.
8. Bowel Control Advisory (2011). Rectum and muscles.