A Study on Various Modes of Excretion

Introduction

Every living thing engages in metabolic processes that produce compounds that, if allowed to build up in the body, could be poisonous. These materials are regarded as excretory wastes. Depending on several internal or external conditions, each organism uses a different technique to remove these wastes. We shall learn more about these excretory processes in this article, including the types of excretory products that each one eliminates.

Excretion and Excretory Wastes

The process of eliminating harmful or non-toxic wastes from the body is known as excretion. Each organism produces various excretory products. For instance, the primary excretory substance in fish is ammonia, whereas the primary excretory substance in humans is urea. These wastes are removed from the body via excretory organs.  Every living organism has a unique excretory system in its body.

For more help, you can refer to Science Class 7 Lesson No 11. Check out the video Lesson for a better understanding.

Methods of Excretion

Nitrogenous wastes produced during protein metabolism are the main excretory products produced by an organism. The conversion of the main nitrogenous waste ammonia results in the final excretory products of an organism. The final excretory products that are eliminated using a particular procedure are used to categorize the various excretion processes.

Ammoniotelic: Ammonia is released as a waste product during ammoniotelic. Because ammonia removal needs a significant amount of water, aquatic creatures like fish, poriferans, protozoans, etc. exhibit ammoniotelic. These creatures are referred to as ammoniotelic organisms.

Ureotelism: Ureotelism is the process of discharging urea as the final excretory waste. In terrestrial species like humans, it is common. A moderate amount of water is necessary for the body to remove urea from it. Ammonia is changed into urea in the livers of ureotelic organisms.

Uricotelism: Uricotelism is the elimination of uric acid, which is the ultimate excretory product. Because uric acid does not dissolve in water, the waste produced by uricotelic organisms is expelled as paste or pellets. Animals, including birds, reptiles, and some insects, exhibit uricotelism.

Guanotelism: Guanine is released as the body’s ultimate excretory product during Guanotelism. Guanine cannot be removed with water since it is an insoluble substance. Guanotelism has been observed in various spider species, as well as some types of earthworms and reptiles.

Aminotelism: The elimination of final waste products in the form of amino acids is known as aminonotelism. Mollusks and echinoderms both use this technique of excretion.

Excretion in Humans

The human body produces urea, uric acid, ammonia, and carbon dioxide as excretory products. Three of these are nitrogenous metabolic wastes that are eliminated in the urine or sweat, but carbon dioxide is a non-nitrogenous metabolic waste that is eliminated in the expired air. Let’s talk in detail about these excretory processes in humans.

Urination: The kidneys and other related organs perform several procedures to remove nitrogenous waste from the body. Urine, the last byproduct of this process, is excreted from the body by micturition. Urine formation happens in three stages. The nephron, which is the kidneys’ functional unit, performs each of these processes.

Glomerular filtration: The renal capsule, a nephron-like structure containing a cluster of blood capillaries, is where the first stage of urine production takes place. In this step, the blood is ultrafiltered, and the majority of the plasma as well as a few other molecules, including wastes, are taken out of it in the form of glomerular filtrate. This glomerular filtrate travels into the nephron’s long renal tubule, where it is absorbable.

Tubular reabsorption: The nephron is a structure that filters blood into a fluid called filtrate, much of which is then reabsorbed into the body. Resorption is a carefully regulated process that is modified to keep blood volume, pressure, plasma osmolarity, and pH in a stable state. Through the peritubular capillaries, reabsorbed liquids, ions, and molecules are restored to the bloodstream instead of being eliminated as urine.

Secretion: In this stage, chemicals like creatinine, hydrogen ions, and drugs are released from the renal tubule walls and transferred to the urine. Each nephron produces urine, which the collecting duct gathers and then excretes through the ureters into the urinary bladder. The urethra is the passageway through which urine exits the body once the urinary bladder has become bloated.

Expiration: Humans expel carbon dioxide through breathing, which is the metabolic waste product created during respiration. During this phase of breathing, the air is expelled through the nostrils.

Sweating: Sweating eliminates extra water, salt, and some urea from the body. This is brought on by the sweat glands in the skin producing sweat.

Examples of Excretion

The human body’s different organs that are responsible for excretion include the kidneys, lungs, large intestine, liver, and skin. A few examples of excretion include the release of bile by the liver, which travels to the small intestine before exiting the body via the large intestine. The large intestine is one organ in the body that excretes solid wastes.

Importance of Excretion in Living Organisms

• The removal of wastes from the body is crucial because if they are left there for an extended period, they can seriously harm the organ systems. 
• For instance, if urea builds up in the body, it can be extremely poisonous and cause uremia. 
• Too much carbon dioxide in the blood will cause carboxyhemoglobin to form and cause the blood to become acidic, which will reduce its ability to carry oxygen. 
• If faecal matter forms in the alimentary canal after the conclusion of absorption is not cleared, it could lead to the accumulation of hazardous bacteria and fermentation products, which could injure or impair the gut’s normal function.

Summary

The process of eliminating harmful or non-toxic wastes from the body is known as excretion. The final excretory products that are eliminated using a particular procedure are used to categorize the various excretion processes. The body produces urea, uric acid, ammonia, and carbon dioxide as excretory products. The human body’s different organs that are responsible for excretion include the kidneys, lungs, large intestine, liver, and skin. The removal of wastes from the body is crucial because if they are left there for an extended period, they can seriously harm the organ systems. 

Frequently Asked Questions  

1. What is Renal Ultrafiltration? When does it Occur?
Ans. One of the kidney processes that dialysis treatment substitutes are the process of ultrafiltration, which involves draining fluid from a patient. When a driving pressure causes fluid to cross a semipermeable barrier, ultrafiltration occurs.

2. Nephrons are made up of different Parts, what are They?
Ans. Each nephron is made up of a proximal tubule, which is a convoluted and straight component, a renal corpuscle (glomerulus inside Bowman’s capsule), an intermediate tubule, a connecting tubule, a distal convoluted tubule, an outer, cortical, and inner medullary collecting ducts, among other structures.

3. Give an example of a Disease that can Develop as a Result of the Buildup of Nitrogenous Waste in the Body.
Ans. A medical disease known as uremia is brought on by the harmful consequences of unusually high levels of nitrogenous chemicals in the blood as a result of the kidneys’ inability to eliminate waste products through the urine.

4. What Happens if Excess Carbon Dioxide Accumulates in the Blood?
Ans. Too much carbon dioxide in the blood will cause carboxyhemoglobin to form and cause the blood to become acidic, which will reduce its ability to carry oxygen.