Excretion means getting rid of waste materials or products out of the body system or cells.
It is one of the notable characteristics of living things and a play a crucial role in survival of organisms. Excretion only applies to waste materials that have been truly being inside of the body even for a short while and were only released by metabolic reactions and processes.
Take for instance, when food is eaten, it travels down the alimentary canal to the anus. As it travels down the tube, not every part of it is absorbed to the body system because in actual sense not every particles of the consumed food passes through the digestive system and got transferred to the blood or even the body cells.
This means that the waste from the digestive system which animals including (human) get rid as faeces, does not count as excretion because it has never been part of the body.
In a nutshell, getting rid of faeces from the body does not count as excretion.
Excretion includes all the waste substances that organisms make in their cells plus any excess substances that have been part of the body.
Excretion in humans include the following processes;
1- Carbondioxide released by the body cells in respiration
2- Urea a nitrogenous waste released by the liver after the breakdown of protein foods.
3- Excess water that is not useful to the body.
Urea
When any food that contains protein is eaten, this food is broken into smaller molecules by the digestive system.
These smaller molecules goes into the blood till it reaches the liver. At the liver any excess smaller molecules is converted to urea. Urea itself, is transported in the blood to the kidney.
The urea is removed from the blood by the kidney in the excretory system. The system of function of the kidney is known as the renal system. Renal means something that has to do with kidney.
The Human Urinary System
A kidney is one of the pair of a bean-shaped organ located in the abdomen which helps to remove waste and extra water from the body as urine.
As the blood flow through the kidneys, they filter the blood in order to remove poisonous substances in it which include the urea and even excess water from the blood.
Ureter s the tube that carries the urine made in each kidney to the urinary bladder
The urinary bladder is a hollow organ that holds urine temporarily for a while before excretion.
The urethra is a tube that allows the urine to pass outside of the body to external surroundings.
Urine itself is a mixture of urea produced by the liver and excess water filtered by the renal system.
That's all as regards the brief introduction regards excretions in humans and happy blogging and social interactions as it is.
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