Transportation in Animals and Plants

Human Excretion

Every organism depends on a series of basic processes to live a normal life. These processes include the respiratory system, the circulatory system, the excretory system and more. Excretion is an important part of an organism’s body. Different organisms follow different methods and modes of excretion. Let us know more about human excretion.

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Excretory System

Due to cellular respiration, a lot of gases and other waste products are produced inside an organism’s body. They must be removed properly and periodically. Without their removal, they can prove harmful to the human body as they can be toxic to the body.

excretory system

Excretion is this process of removal of wastes that are produced within a body. There are various organs that help in excretion of such wastes from our body. They are kidney, lungs, skin, eyes, etc.

We know that blood transports food, air, and water to different parts of our body. It also carries waste products. The human body consists of a specialized system which purifies the blood. This system is known as excretory system. An excretory system is basically composed of the following components:

  • A pair of kidneys
  • A pair of ureters
  • Urinary bladder
  • Urethra

Let us discuss the human excretory system more in-depth.


Kidneys are bean-shaped organs in the human body. They play a vital role in the excretory system of our body. They basically act as filters in our body. Blood contains both useful and harmful substances.

Kidneys play an important role in separating useful substances by re-absorption and toxic substances by forming urine. Capillaries, which are a type of blood vessels in the kidneys, help in filtering the blood and wastes materials. It then converts these into the urine.

Urinary Bladder, Ureter, and Urethra

Urine, thus formed, passes on to the urinary bladder via ureter. Through the urinary opening at urethra, we excrete urine. Urine consists of 95% water, 2.5% urea and 2.5% other wastes. This system expells from time to time.

Type of Waste and Mode of Excretion

Protein mainly consists of nitrogen. Thus, the metabolism of protein creates nitrogenous wastes in the body. The nitrogenous waste is the primary form of waste in animals. This nitrogenous waste can take different forms in different types of animals. The types of this waste include ammonia, urea, and uric acid. Based on the type of nitrogenous waste, we can divide animals into the following major categories:

  • Ammonotelic: These animals have ammonia as the main nitrogenous waste. These are typically aquatic animals, e.g. fish, frogs, etc. These animals require a lot of water to remove the wastes.
  • Ureotelism: These animals produce urea as the main nitrogenous waste. Common examples include mammals that need less water.
  • Urecotellism: In these animals, uric acid is the main nitrogenous waste. Examples include reptiles that need negligent amounts of water.

Question For You

Q1. Which is the main excretory organ in humans?

Ans: Kidneys

Q2. Which is the main excretory product in humans?

Ans: Urea

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