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Egestion and excretion are the processes by which waste products are removed from the body. The primary difference between Egestion and Excretion is that Egestion is the process of removal of undigested matter from the digestive process. Excretion, on the other hand, is the process by which metabolic waste products are expelled.
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Key Terms: Excretion, egestion, excretion meaning, excretory system
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What are Excretion and Egestion?
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To support its survival, an organism maintains a variety of metabolic activities. To survive, the creature, whether it is a plant or an animal, must consume or prepare nourishment. It is the most basic process of surviving in an ecosystem.
(Egestion & Excretion)
Many by-products are created inside the organ system during this process. To maintain optimal functionality, this system must be cleansed. To prevent system toxicity and continue to survive in the environment, a plant or animal must eliminate such by-products.
Excretion is the process by which an organism excretes a metabolic by-product through various cellular and organ processes.
The term egestion, on the other hand, refers to the expulsion or evacuation of undigested food from an animal's digestive tract. It is similar to the method of removing waste products from a metabolic process, but it involves the digestive system and occurs only in animals.
Process of Egestion
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Egestion is the process of removing undigested food from the body of an animal. Unused food is ingested in different ways by different groups of animals.
Undigested food is carried to the cell membrane and discharged outside of the body in unicellular organisms. A digestive system is not present in all multicellular creatures. The food is processed in the stomach sac of the hydra, and the undigested food is spat through the mouth.
The digestive system of higher animals is extensively developed and specialised. Following digestion and absorption in the small intestine, food that has not yet been digested and absorbed travels to the large intestine.
(Egestion in Human Beings)
The remaining water, electrolytes, and several vitamins are absorbed in the large intestine. There is no digestive function in the Large Intestine. Many bacteria can be found here breaking down some undigested molecules which create certain vitamins.
A portion of the food would be left undigested and unabsorbed. It has to be taken out of the body. The remnants of unprocessed food build up in the colon. They are ejected from the body on a regular basis via the colon and the anus (or the cloaca). The contents are pushed to the anus by peristaltic waves. Because most of the water is used by the animal body, the expelled unutilized food particles are semisolid or thick.
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Process of Excretion
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Excretion is the process of removing waste materials produced in the cells of animals and plants. The organisms maintain acid-base balance and control osmotic pressure through this process. Substances that have gone through several metabolic processes inside the cells are excreted. Exhalation, sweating, and urination are examples of excretory processes in mammals.
(Organs of Excretion)
Urination is the primary excretory function. Food digested in the digestive tract undergoes various chemical modifications after entering the cells. Waste products, particularly uric acid, are generated during these reactions. It is damaging to the body and is thus eliminated by excretion.
Excretion occurs in each cell of unicellular organisms and Cnidarians, and there are no particular excretory structures.
The flatworms have a specific excretory system. Excretion occurs directly from the secretory organs to the environment in animals without a circulatory system.
Excretion in Vertebrates
The excretory system and organs of vertebrates are well developed. When the blood travels through the kidneys, the waste products from the cells fall into the blood and are discharged.
(Excretory System in Human Beings)
The kidneys filter the blood for salts, urea, and excess water, which they expel in the urine. The ureter collects urine from the kidney and transports it to the urinary bladder. The urine is kept there until it is urinated and then discharged into the environment via the urethra.
Types of Excretory organs
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Other than kidneys, the skin and lungs also act as principal excretory organs.
- Sweat is produced by sweat glands in the skin. This is made up of water, urea, and salt. Sweating helps to keep the body cool in hot weather.
- When you breathe out, your lungs expel excess carbon dioxide (along with some water vapour).
Excretion in Plants
The emission of carbon dioxide and oxygen through the stomata is the process of excretion in plants.
Waste materials are also accumulated by plants in the cells of their leaves (as crystals). When the leaves fall off the plant, they are removed.
Difference between Egestion and Excretion
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The following is a list of the differences between egestion and excretion:
| Egestion | Excretion |
|---|---|
| The procedure entails eliminating undigested waste products and food from the organism's body. | The procedure entails eliminating waste from an organism's cells. |
| Undigested food and other harmful substances leftover from digestion are referred to as discharged materials. | Metabolic wastes, such as carbon dioxide or oxygen, are the discharged materials. |
| Egestion is primarily accomplished through the anus or mouth. (Animals like jellyfish use their mouths to both eat and expel waste.) | The urethra, the nose, and the skin are all used for excretion. |
| Egestion is a process that only animals go through. | Excretion is a process that occurs in both plants and mammals. |
The types of wastes expelled from an organism explain the difference between excretion and egestion. Thus, the undigested food that remains after digestion is excreted by animals during the egestion process and excretion is the process in which metabolic wastes are expelled by both plants and animals.
Things to Remember
- Egestion is the process of the undigested food being discharged from the animal's body.
- Excretion is the process of removing waste materials produced in the cells of animals and plants.
- The material expelled during egestion is undigested food, whereas metabolic waste is discharged during excretion.
- The material that was expelled during the egestion process did not pass through the cells. The material that was expelled during the excretion process has passed through the cells.
- In multicellular animals, egestion occurs through the mouth or anus, while excretion occurs by the nose/mouth, skin, and urethra.
- Egestion is only done by animals, whereas excretion is done by both plants and animals.
Previous Year Questions
- A decrease in blood pressure / volume will not cause the release of :….[NEET 2017]
- Angiotensinogen is a protein produced and secreted by-...[NEET 2006]
- Brush border is characteristic of...[NEET 1990]
- Concentration of urine depends upon which organ?….[NEET 2000]
- Glucose is taken back from glomerular filtrate….[NEET 1993]
- Human urine is usually acidic because...[NEET 2015]
- In ureotelic animals, urea is formed by...[NEET 1997]
- In which one of the following organisms its excretory organs are correctly stated?...[NEET 2010]
- Uric acid is the chief nitrogenous component of the excretory products of...[NEET 2009]
- Which of the following options is the most appropriate?...[NEET 2019]
- Which of the following does not favour the formation of large quantities of dilute urine?...[NEET 2015]
- Which of the following factors is responsible for the formation of concentrated urine ?...[NEET 2019]
- Which one of the four parts mentioned below does not constitute a part of single uriniferous tubule?….[NEET 1994]
- Which one of the following options gives the correct categorisation of animals according to the type of nitrogenous waste they give out?...[NEET 2012]
- Which one of the following is not a part of a renal pyramid?….[NEET 2011]
Sample Questions
Ques. What is the primary distinction between egestion and excretion? (2 marks)
Ans. Egestion is a process that occurs in animals with a digestive system. Plants do not have tissues or organs that operate as the digestive system, hence it does not happen to them. Byproducts are removed in a variety of ways. Animals, on the other hand, can both eat and excrete, but plants can only excrete.
Ques. Which components of the body are involved in digestion? (2 marks)
Ans. Undigested food is usually ejected at the conclusion of the digestive tract by animals. Advanced creatures use their anus to egest, but primitive animals like starfish use their lips to do so.
Ques. Where does excretion take place? (2 marks)
Ans. Animals usually regurgitate undigested food at the end of their digestive tract. Advanced organisms egest with their anus, but primitive animals like starfish egest with their lips.
Ques. Explain the mode of nutrition in amoeba. (2 marks)
Ans. Amoeba is a unicellular animal that follows the holozoic mode of nutrition. In holozoic nutrition, the digestion of food follows after the ingestion of food. Thus, digestion takes place inside the body of the organism. Holozoic nutrition happens in five steps, viz. ingestion, digestion, absorption, assimilation and egestion.
Ques. Explain the functions of the large intestine. (2 marks)
Ans.
- The large intestine is smaller than the small intestine.
- Undigested food goes into the large intestine.
- Some water and salt are absorbed by the walls of the large intestine. After that, the undigested food goes to the rectum, from where it is expelled out through the anus.
- The large intestine absorbs excess water. The rest of the material is removed from the body via the anus. (Egestion).
Ques. How is the small intestine designed to absorb digested food? (2 marks)
Ans. The small intestine is designed to provide maximum area for absorption of digested food and its transfer into the blood for its circulation into the body. For this, the inner lining of the small intestine has numerous finger-like projections called villi. The villi are richly supplied with blood vessels which take the absorbed food to each and every cell of the body.
Ques. What is the role of saliva in the digestion of food? (2 marks)
Ans. Saliva contains a salivary amylase enzyme that breaks down starch into sugars like maltose.
Saliva keeps the mouth cavity clean and moistens the food that helps in chewing and breaking down the big pieces of food into smaller ones.
Ques. What are the methods used by plants to get rid of excretory products? (2 marks)
Ans.
(i) The plants get rid of gaseous products through stomata in leaves and lenticels in stems.
(ii) The plants get rid of stored solid and liquid waste by shedding off leaves, peeling off bark and felling off fruits.
(iii) The plants get rid of wastes by secreting them in the form of gums and resins.
(iv) Plants also excrete some waste substances into the soil around them.
Ques. How is the amount of urine produced regulated? (2 marks)
Ans. The amount of urine is regulated by the kidney. It depends on the quantity of excess water and wastes dissolved in water.
(i) Quantity of water: When water is abundant in the body tissues, large quantities of dilute urine is excreted out. When water is less in quantity in the body tissues, a small quantity of concentrated urine is excreted.
(ii) Quantity of dissolved wastes: Dissolved wastes, especially nitrogenous wastes, like urea and uric acid and salts are excreted from the body. When there is more quantity of dissolved wastes in the body, more quantity of water is required to excrete them. Therefore, the amount of urine produced increases.
(iii) Hormones: The amount of urine produced is also regulated by certain hormones which control the movement of water and Na+ ions in and out of the nephrons.
Ques. Explain the nutrition in human beings. (2 marks)
Ans. The alimentary canal is a long tube extending from the mouth to the anus. Nutrition in human beings is divided into five steps:
- Ingestion: Intake of food from an outside source. Teeth & saliva crush the food to generate the particles of same size & texture. The food is then passed to the stomach via the oesophagus. The peristaltic movements occur all along the gut which helps in pushing the food forward.
- Digestion: In the mouth, salivary amylase helps in carbohydrates digestion. In the stomach, pepsin helps in protein digestion. However, the small intestine is the main site of the complete digestion of carbohydrates, proteins & fats. It receives pancreas and liver secretions. Bile juice emulsifies fats and pancreatic enzymes, trypsin & lipases digest proteins & emulsified fats. It finally converts proteins to amino acids, complex carbohydrates into glucose & fats into fatty acids & glycerol.
- Absorption: The digested food is taken up by the walls of the intestine. The inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption. The large intestine absorbs water from the unabsorbed food.
Ques. What is excretion? (2 marks)
Ans. The biological process involved in the removal of harmful metabolic wastes from the body is called excretion.
Many unicellular organisms remove these wastes by simple diffusion from the body surface into the surrounding water. However, complex multicellular organisms use specialised organs to perform this function.
Excretion in Human Beings: The excretory system includes a pair of kidneys, pair of ureters, urinary bladder & urethra.
Ques. Describe the factors on which heterotrophic nutrition depends. (2 marks)
Ans. Heterotrophic Nutrition: Heterotrophs depend on other organisms for their nutrition.
- Saprophytes: They break down the food material outside the body and then absorb it, also termed extra-cellular digestion. E.g. fungi like bread moulds, yeast, mushrooms etc.
- Parasites: Derive nutrition from plants or animals without killing them. E.g. Cuscuta (Amar-bel), ticks, lice, leeches, tapeworms etc.
- Holozoic Nutrition: These organisms take in whole material & break it down inside their bodies. E.g. cow, deer, lion, tiger, humans etc. What can be taken in and broken down depends on body design and functioning
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