Difference Between Ingestion and Egestion

Main Difference – Ingestion vs Egestion

Ingestion and egestion are two events that occur during the feeding of animals and protozoa. The main difference between ingestion and egestion is that ingestion is the intake of food into the body whereas egestion is the elimination of wastes out of the body. Ingestion occurs through the mouth in animals. In protozoa, ingestion occurs by endocytosis. After taking food into the digestive system of animals, mechanical digestion and chemical digestion occurs to break down food into smaller constituents that can be absorbed by the body. Protozoa take food into a vesicle and digest it inside the vesicle by digestive enzymes. The elimination of wastes of the digestion occurs through the anus in animals. In protozoa, the egestion occurs by exocytosis.

Key Areas Covered

1. What is Ingestion
      – Definition, Types, Mechanism
2. What is Egestion
      – Definition, Types, Mechanism
3. What are the Similarities Between Ingestion and Egestion
      – Outline of Common Features
4. What is the Difference Between Ingestion and Egestion
      – Comparison of Key Differences

Key Terms: Animals, Digestion, Digestive System, Egestion, Endocytosis, Exocytosis, Ingestion, Phagocytosis, Protozoa

What is Ingestion

Ingestion refers to the mechanisms of taking food and water into the body by swallowing or absorbing them. In animals, ingestion occurs through the mouth. Ingestion can not only include the intake of food but also the intake of unhealthy materials such as pathogens (bacteria, virus, fungi, and parasites) and toxic materials to the body. Vomiting is the opposite action of ingestion in which the unwanted or toxic materials are eliminated through the mouth. After ingestion, the food particles enter the digestive system. The digestion of food occurs in two methods: mechanical digestion and chemical digestion. During mechanical digestion, food is broken down into small particles. Chemical compounds in food are broken down into smaller compounds during the chemical digestion. Both mechanical and chemical digestion facilitate the absorption of nutrients by the body. The physiology of the digestive system of animals is shown in figure 1.

Difference Between Ingestion and Egestion

Figure 1: Animal Digestive System

Protozoa are a type of unicellular eukaryotic animals. Their ingestion of food particles occurs by endocytosis. They use two endocytic pathways: phagocytosis or pinocytosis for ingestion. In phagocytosis, pseudopodia are formed surrounding the food particle. The food particle is taken into the cell by forming a phagosome. In pinocytosis, food particles along with the surrounding fluid is taken into the cell by the formation of vesicles by the plasma membrane. The digestion of food occurs inside the vesicles in protozoa.

What is Egestion

Egestion refers to the expulsion of the undigested material of food from the body. It is the final step of feeding of animals and protozoa. Semi-solid feces are eliminated by the digestive tract of animals through the anus in egestion. Feces may include indigestible food such as fibers, dead cells as well as pathogens. It is made in the large intestine and is stored sometimes in the rectum before elimination.

Figure 2: Phagocytosis

In protozoa, egestion occurs by exocytosis. In exocytosis, a secretory vesicle containing the undigested material fuses with the plasma membrane and eliminates the unwanted material into the extracellular environment. Ingestion, digestion, and egestion of protozoa are shown in figure 2.

Similarities Between Ingestion and Egestion

Both ingestion and egestion are two events of the feeding of animals and protozoa.
Both ingestion and egestion are important in taking nutrients into the body and elimination of unwanted materials from the body.

Definition

Ingestion: Ingestion refers to the mechanisms of taking food and water into the body by swallowing or absorbing them.

Egestion: Egestion refers to the expulsion of the undigested material of food from the body.

Process

Ingestion: Ingestion is the intake of food into the body.

Egestion: Egestion is the elimination of the waste from the body.

Occurrence

Ingestion: Ingestion occurs through the mouth.

Egestion: Egestion occurs through the anus.

In Protozoa

Ingestion: The ingestion of food occurs by phagocytosis or pinocytosis in protozoa.

Egestion: The egestion of food occurs through the exocytosis in protozoa.

Correlation

Ingestion: Ingestion is the first event in feeding.

Egestion: Egestion is the final event in feeding.

Role

Ingestion: Nutrients and water can be taken into the body through ingestion.

Egestion: Egestion helps to remove unwanted materials from the body.

Conclusion

Ingestion and egestion are the first and final steps of the feeding of animals and protozoa. Ingestion is the intake of food into the body whereas egestion is the elimination of the undigested materials from the body. This is the main difference between ingestion and egestion.

Reference:

1.“Ingestion: Definition & Process.” Study.com, Available here.
2. “Egestion.” Egestion – RightDiagnosis.Com, Available here.
3. “Nutrition and Protozoa (With Diagram).” Biology Discussion, 2 May 2016, Available here.

Image Courtesy:

1. “Anatomy and physiology of animals From ingestion to egestion” – original uploader was Sunshineconnelly at English Wikibooks – Transferred from en.wikibooks to Commons by Adrignola using CommonsHelper (CC BY 3.0) via Commons Wikimedia
2. “Figure 04 04 04” By CNX OpenStax (CC BY 4.0) via Commons Wikimedia