Summary Life Sciences (Biology) - Human excretory system

EXCRETORY SYSTEM:




WHAT IS EXCRETION:
 Excretion is the removal of waste products from the body that was formed during
metabolic reactions.
 These products include:
- Water
- Carbon dioxide
- Nitrogenous waste
 If these substances accumulate they can become toxic and cause damage to
body tissues.
 Some substances like water don’t become toxic but they disrupt homeostasis
 Homeostasis = maintaining the internal environment of the body at a steady rate
so that it can function properly.




THE LIVER:
 The liver is not an excretory organ
 But many waste products are formed here
 Then sent and excreted elsewhere

Nitrogenous waste:
 Urea
- is formed from excess amino acids
- Main waste excreted by the kidney

 Uric acid:
- Formed from the breakdown of nucleic acids

 Creatinine:
- Found in skeletal muscle cells
- Formed from creatinine phosphates




Non- nitrogenous waste:

,  Toxins and drugs
- Painkillers
- Nicotine
- Tranquilizers

 Alcohol
- Toxic to cells
- Causes permanent damage to the liver cells (cirrhosis)


Other excretory products:
 bile pigments
- formed from breakdown of red blood cells
- stored in gall bladder

 cholesterol
- formed from breakdown of bile salts

 to maintain homeostasis it is important to rid of any waste products which can
diffuse into the blood stream
 They are carried to the excretory organs where they will be expelled.


EXCRETORY ORGANS:

1. Kidneys:
- Excrete all of the nitrogenous waste products formed in liver
- Mostly urea
- Also excrete non-nitrogenous waste such as CO2, excess water, ions ,
hormones, poisons and drugs
- Anything that can be diffused into the blood stream

2. Lungs:
- Excretes all CO2 produced from respiration in the body
- Exhaled when breathing out
- Small amounts of water is also excreted




3. Skin:
- Water, salts and small amounts of urea is excreted in form of sweat