Egestion in Animals

Egestion refers to the act of excreting unwanted or undigested material from a cell, just as in the case of single-celled organisms, or from the digestive tract of multicellular animals. The term egestion comes from the Latin word ēgest  meaning “to carry out”. Not only humans but other organisms also who rely on food to survive have certain methods by which they remove wastes out of their bodies. For microscopic organisms like amoeba to large animals like humans, they all consume food and have a way of removing the food. This article is primarily written on the topic of egestion. The article follows and explains what egestion is, what the process of egestion consists of and a basic difference between egestion and excretion. 

Egestion

In humans and other higher forms of animals, the egestion process describes the waves of muscular contractions of the colon walls thereby, moving the faecal matter towards the rectum. The faecal matter gets temporarily stored in the rectal ampulla. Once the faecal matter gets accumulated, the rectal walls begin to expand. This leads the stretch receptors in the rectal walls to stimulate, and the rectal muscles to contract by reflex, the internal anal sphincter to relax, and further the external anal sphincter skeletal muscle to contract. Due to which there develops an urge to expel the faeces. If not acted upon, it leads to reverse peristalsis where the material returns to colon for further water absorption and storage until the next waves of muscular contractions of the transverse and descending colon occurs. During defecation, air is expelled against a closed airway. This leads the lungs to stop ventilation as it pushes the chest diaphragm downwards. This develops  pressure on the digestive tract.

Egestion vs. excretion

Excretion mainly refers to the process, act or function of ejecting waste products of metabolism, specifically from the system of an organism.

Both egestion and excretion leads to the act or process of getting rid of wastes from the cell or body. Moreover, egestion shall never be confused with excretion as egestion is particularly defined as getting rid of waste that is formed from the chemical reaction of the body, like in urine, sweat, etc.

Therefore, excretion in humans and other multicellular animals can be carried out via the kidneys and skin. Basically, egestion refers to the removal of undigested wastes via discharging or expelling them from the digestive tract through the anus. Whereas in plants, they do not egest as they lack a digestive system for egestion. The waste products of plants are released from the plant largely through the stomata and hydathodes. The excess oxygen that is brought by the phloem and xylem tissues is to be excreted through the stomata. Transpiration (also occurs via stomata) and guttation (through the hydathodes) are few examples of the ways by which plants excrete waste.

Importance of egestion

Egestion is an important process in humans and animals as it is the only means to dispose of the undigested food out of the system. If bowel movement is willingly delayed for longer periods, this may lead to a megacolon and can eventuate to bowel rupture.

Egestion disorders

When the faecal material is delayed over a longer period of time, it may harden from water absorption. The evacuation of such faeces may turn out to be difficult. This condition is known as constipation. When the faecal material still comprises excess liquid then it is evacuated too fast and frequently this condition is known as diarrhoea.

Conclusion

Various groups of animals egest the undigested food in an unusual way. Among the unicellular organisms, the undigested food is transported up to the cell membrane and then released outside of the body. Some multicellular animals do not possess a specialized digestive system. As it can be seen, in hydra, the food gets digested in the stomach sac, and the undigested food is egested out through the mouth. We hope that this article was able to explain everything that there is to be known about what the process of egestion is. We also tried to clear all the important doubts that many students have about the difference between egestion and excretion. We suggest you focus more on understanding the topic rather than just mugging it up.