Excretory Products and their Elimination

Excretory Products and Their Elimination

Edited By Team Careers360 | Updated on Sep 03, 2024 03:33 PM IST

What Is Excretion?

Excretion is the process of biological nature through which an organism expels waste products arising from metabolic activities. In light of this explanation, this becomes an important function that ensures no accumulation of toxic substances takes place to disrupt cellular processes.

The excretory system helps in maintaining homeostasis—a stable internal environment—which Feldherr refers to as the "adjustments that allow an organism to survive in its environment." It does its excretory role by regulating the composition and volume of body fluids to attain electrolyte balance, remove metabolic wastes, and maintain proper pH levels in the body.

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Excretory Products and Their Elimination

Types Of Excretory Products

These excretory products can be broadly classified into two categories:

Metabolic waste products

Urea
Uric acid
Ammonia
Carbon dioxide
Water

Non-metabolic waste products

Bile pigments
Excess salts

Examples

Urea: This is synthesised in the liver from ammonia.
Uric acid: It is the product formed from the degradation of nucleotides.
Ammonia: It is a poisonous product of protein metabolism.
Carbon dioxide: This is the byproduct of cellular respiration.
Water: It is eliminated in the urine, in sweat, and in the breath.
Bile pigments: These are derived from the breakdown of haemoglobin.

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Excretory Systems In Different Organisms

Different organisms developed different excretory systems to adapt to habitat conditions and styles of life.

Simple organisms:

Protozoa: The contractile vacuoles
Hydra: Diffusion

Invertebrates:

Earthworms: Nephridia
Insects: Malpighian tubules

Vertebrates:

Fish: Gills and kidneys
Amphibians: Skin and kidneys
Reptiles: Kidneys
Birds: Kidneys and cloaca
Mammals: Kidneys

Human Excretory System

The excretory system of humans consists of various organs interplaying with each other to excrete waste products.

Components of the human excretory system:

Kidneys
Ureters
Urinary bladder
Urethra

Structure and functions of kidneys:

Cortex and medulla
Nephron: The functional unit

Process of urine formation:

Glomerular filtration
Tubular reabsorption
Tubular secretion

Hormones regulating urinary secretion:

ADH (Anti-diuretic hormone)
Aldosterone

Other Excretory Organs Of Humans

Humans have other excretory organs besides the kidneys.

Skin

The sweat glands excrete water, salts, and a little urea.

Lungs

Carbon dioxide and water vapour are expelled through respiration.

Liver

Converts ammonia to urea.
Breaks down haemoglobin to form bile pigments.

Disorders Of The Excretory System

The excretory system may be prone to various disorders, thereby hampering the normal functioning of the system.

Kidney stones: Minerals getting solidified to become painful and blocking.
Urinary tract infection (UTI): Infection in the urinary system by bacteria.
Glomerulonephritis: Kidney disorders where glomeruli are inflamed.
Chronic kidney disease (CKD): Gradual loss of kidney function over time.

Comparative Study Of Excretory Products

Nitrogenous wastes produced by different organisms are of various types.

Ammonotelic organisms: Those that excrete ammonia; for example, most aquatic animals.
Ureotelic organisms: Those that excrete urea; for example, mammals and amphibians.
Uricotelic organisms: Those that excrete uric acid; for example, birds and reptiles.
Evolutionary significance: Adaptations to save water and detoxify wastes efficiently.

Role Of Excretory System In Osmoregulation

Osmoregulation refers to the maintenance of the water and electrolyte balance of an animal's body.

Maintenance of proper host salt–water balance.
Range from simple diffusion in single-celled organisms to complex systems in vertebrates.
Ensure survival both in fresh water and in terrestrial ecosystems.

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Frequently Asked Questions (FAQs)

1. Which are the principal excretory products in human beings?

The chief excretory products in humans are urea, uric acid, ammonia, carbon dioxide, water, and bile pigment.

2. How does a human kidney work?

A human kidney filters blood against waste products and converts other surplus materials into urine through mechanisms like glomerular filtration, tubular reabsorption, and tubular secretion.

3. What are ammonotelic, ureotelic, and uricotelic animals?.

The excretion of either ammonia in ammonotelic organisms, urea in ureotelic organisms, or uric acid in uricotelic organisms. These changes are by and large adaptive to the environment and availability of water.

4. What are the causes of kidney stones and the means of their prevention?

Kidney stones are formed in the urine due to the crystallisation of minerals. They are preventable with good body hydration and reduced salt and other dietary factors.

5. What is the role of ADH in the excretory system?

ADH, antidiuretic hormone, is a hormone regulating the human body's content of water. It does this by increasing the quantity of water reabsorbed in the kidneys, hence decreasing the volume of urine.