Numerous chemical activates ⇒ occur within body cells all the time. ⇒ called metabolic activities.
some metabolic activities ⇒ produce substances that are harmful or toxic to the body ⇒ they are called metabolic waste products or excretory products → these + substances that are not needed have to be removed
Metabolism = Anabolism + catabolism
- Metabolism → all the chemical activities within the body
- Anabolism → activities within cells where simpler substances are built up into more complex ones (eg: conversion of glucose to glycogen, formation of new protoplasm from amino acids)
- Catabolism → chemical processes which cause the breakdown of complex substance into simpler ones (eg: tissue respiration, deamination of amino acids to from urea in the liver (Functions of the Liver)
Egestion vs Excretion
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Egestion is the removal of undigested matter from the alimentary canal. The bulk of the faeces is not formed from a substance within the cell. Hence not a result of metabolic changes.
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Excretion is the removal of metabolic waste product, toxic substances and substance in excess of Body’s requirement
Some Metabolic Waste Products
Examples of Metabolic Waste Products
What is Excretion
Definition
Definition: Excretion is the removal of metabolic waste products, Toxic substances and substances in excess of the body’s requirements #BiologyDefinitions
| Excretory Products | Excretory Organs | Excreted as |
|---|---|---|
| carbon dioxide | lungs | Gas in expired air |
| excess mineral salts | kidneys Skin | Constituent of Urine Constituent of Sweat |
| excess water | Kidneys Skin | Constituent of Urine Constituent of Sweat |
| urea | Kidneys Skin | Constituent of Urine Constituent (traces) of Sweat |
| Why is excretion important | ||
| Body → excreted metabolic waste products (eg urea) and toxic substances. | ||
| ⇒ so that they do not accumulate to a level that becomes harmful to the body |
What Makes up the Human Urinary System
What Makes up the Human Urinary System
Structure of the Kidney
Structure of a Nephron
How is Urine Formed
Constituents of Urine
Constituents of Normal Urine
- per 100ml of urine
- Water - 96.0g
- Mineral salts (mainly NaCl) - 1.8g
- Urea - 2.0g
- Other nitrogenous substances - 0.2g
- Total - 100g
Conditions where urine concentration is different
- Protein rich diet → results in more urea being present in the urine (amino acids deaminated in liver to form urea)
- Large intake of water or water rich food - increase water volume in blood
- Thus, more urine formed (every 100ml of liquid taken in by body will result in 100ml of liquid being expelled out i.e. in the form of urine, sweat saliva, etc.)
- Very hot weather → less urine formation as most will be lost as sweat
- During Cold weather → pores on body will close up leaving urine the only way of excreting liquid
- excess salt from salt rich food can be found in urine
- Sugar may appear in urine after heavy intake of glucose rich food
Abnormal Constituents of Urine
- Diabetes mellitus
- urine containing large amounts of glucose
- Body unable to store excess glucose in the form of glycogen
- May be due to inability of pancreas to secrete insulin (Type 1) which is needed to convert glucose to glycogen
- May be due to defective insulin being produced (Type 2)
- Glucose filtered off in the glomerular filtrate but kidney tubules were unable to reabsorb all the glucose fast enough
Osmoregulation
What Happens when Kidneys Fail
What Happens When Kidneys Fail