May 12, 2021

Excretory System Short Notes PDF

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Excretory System Notes PDF- Hello Aspirants, welcome to our site Today, we are providing you human excretory system Short notes PDF which helps you to understand this topic for competitive exams.

Excretory System:

  • Every living organism generates waste materials in its body and has a mechanism to expel it.
  • The waste products that are produced are urea, uric acid, ammonia, carbon dioxide, water, and ions like sodium, potassium, chloride, phosphates, etc.
  • Ammonia, urea, and uric acids are the major sources of Nitrogenous Wastes.
  • The most toxic substance, ammonia requires more amount of water for its elimination whereas uric acid, which is less toxic, requires less water.
  • Kidney disease and kidney problems are usually treated by a nephrologist. Sometimes kidney stones are treated by a urologist.

Modes of Excretion in Animals:


  • The process of elimination of ammonia from the body is known as ammonotelism and the organisms which exhibit this nature are called ammonotelic. Example: bony fishes, insects, etc.
  • Ammonia is quite soluble, so it is excreted in the form of ammonium ions either by a simple diffusion process across the body surface or through the gills.


  • In some mammals and amphibians, urea is excreted and is called ureotelic.
  • In these organisms, ammonia that is produced is converted to urea in the liver of the animals and it’s released in the blood which is filtered and released out by the kidneys.
  • It helps to maintain the osmolality in the body.


  • The process of elimination of uric acid from the body as the main nitrogenous waste material is called uricotelism.
  • Animals who exhibit this kind of elimination are called ureotelic animals. Example: Reptiles, birds, snails
  • Other Nitrogenous wastes are – Allantosm, creatine, creatinine and hippuric acid are some other nitrogenous waste products excreted by mammals.


  • The skin helps in excretion wastes by the way of sweat.
  • It eliminates waste compounds of NaCl and some amount of urea etc.
  • Lungs are the primary respiratory organs and they help intake oxygen and expel carbon dioxide (CO2).
  • In respiration, lungs also function to eliminate some amount of water from the body in the form of vapor.
  • The liver has an important function in the excretion of wastes from the body.
  • It changes the decomposed hemoglobin of the worn-out RBCs into bile pigments bilirubin and biliverdin.
  • These pigments are passed into the alimentary canal with the bile for elimination in the faces.
  • The liver also excretes cholesterol, steroid hormones, certain vitamins, and through the bile. drugs
  • Urea is formed in the liver by a cyclic process called a urea cycle of the Ornithine cycle.
  • The excess of amino acids in the body is deaminated by an enzyme oxidase, producing ammonia NH3. Ammonia being toxic is converted to Urea.
  • The Kidney is the main organ of the human excretory system.
  • Each individual has a pair of kidneys in his body.

The human “excretory system” comprises of the following the structures:

  • 2 Kidneys
  • 2 Ureters
  • 1 Urinary bladder
  • 1 Urethra
  • Urine is made of water, urea, electrolytes, and other waste products:
  • Some medicines and drugs are excreted in urine and can be found in the urine.
    • 95% water
    • 2% urea
    • 0.35% sodium*
    • 0.6% chloride*
    • 0.15% potassium*
    • 0.25% phosphate
    • 0.25% sulfate
    • 0.1% creatinine
    • 0.05% uric acid

In short, we will say that this topic is very interesting because in this topic we learn about the function of the excretory system in our body. Therefore, we will be providing you human excretory system notes PDF by that you can easily understand this topic.

Interested Candidates can download Biology Excretory System Notes PDF from the below available link.


Excretory System Notes PDF – Download Here

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