Excretory System
Excretion
The removal of waste products from the body
- Water
- CO2
- Nitrogenous waste from metabolic reactions
If certain waste products accumulate they become toxic & cause damage to tissues while others are not toxic but can disrupt
homeostasis
Waste products diffuse into blood stream to be excreted by excretory organs
Homeostasis
“Right conditions” that cells function under
- Right amount of water
- Right amount of solutes
- Right temperature
To maintain homeostasis waste products must be removed through excretion
Excretion vs secretion
Excretion is the removal of useless substances whilst secretion is the removal of useful substances
Liver
Not an excretory organ but a lot of waste products are formed here and excreted elsewhere
- Nitrogenous waste
- Urea (main waste excreted by kidney): excess amino acids that are broken down into ammonia (toxic) then
urea through deamination
- Uric Acid: breakdown of nucleic acids
- Creatinine: formed from creatine phosphate, found in muscle cells
- Non-nitrogenous waste
- Toxins and drugs: painkillers, tranquillisers & nicotine
- Alcohol (toxic to cells): causes cirrhosis of the liver if a lot is drunk over a period of time
All waste goes to kidneys
, Excretory Organs
1. Kidneys
- Excrete all nitrogenous & non-nitrogenous waste formed in liver
2. Lungs
- CO2 released from cellular respiration is carried to lungs in blood and exhaled when we breathe out
- Little water and heat is also excreted
3. Skin
- Water, salts and urea released as sweat from sweat glands
- As water in sweat evaporates heat is lost and body is cooled
- Sweat is an excretion and a secretion as it also helps maintain body temperature
4. Alimentary Canal
- Bile pigments (form breakdown of blood cells) & cholesterol are made in liver
- They pass through small intestine and are excreted from colon as bile pigments in faeces
- Mucus and bacteria also excreted in faeces
Urinary System
Main function: to maintain homeostasis by regulating volume & concentration of fluids by filtering and reabsorbing materials
from blood
Structure
Found in the abdominal cavity
- The right kidney is slightly lower than the left as it is pushed down by the larger right lobe of the liver
- The males urethra passes through the penis and carries urine & semen
- The female's urethra carries only urine through a separate opening in front of the vaginal opening
Excretion
The removal of waste products from the body
- Water
- CO2
- Nitrogenous waste from metabolic reactions
If certain waste products accumulate they become toxic & cause damage to tissues while others are not toxic but can disrupt
homeostasis
Waste products diffuse into blood stream to be excreted by excretory organs
Homeostasis
“Right conditions” that cells function under
- Right amount of water
- Right amount of solutes
- Right temperature
To maintain homeostasis waste products must be removed through excretion
Excretion vs secretion
Excretion is the removal of useless substances whilst secretion is the removal of useful substances
Liver
Not an excretory organ but a lot of waste products are formed here and excreted elsewhere
- Nitrogenous waste
- Urea (main waste excreted by kidney): excess amino acids that are broken down into ammonia (toxic) then
urea through deamination
- Uric Acid: breakdown of nucleic acids
- Creatinine: formed from creatine phosphate, found in muscle cells
- Non-nitrogenous waste
- Toxins and drugs: painkillers, tranquillisers & nicotine
- Alcohol (toxic to cells): causes cirrhosis of the liver if a lot is drunk over a period of time
All waste goes to kidneys
, Excretory Organs
1. Kidneys
- Excrete all nitrogenous & non-nitrogenous waste formed in liver
2. Lungs
- CO2 released from cellular respiration is carried to lungs in blood and exhaled when we breathe out
- Little water and heat is also excreted
3. Skin
- Water, salts and urea released as sweat from sweat glands
- As water in sweat evaporates heat is lost and body is cooled
- Sweat is an excretion and a secretion as it also helps maintain body temperature
4. Alimentary Canal
- Bile pigments (form breakdown of blood cells) & cholesterol are made in liver
- They pass through small intestine and are excreted from colon as bile pigments in faeces
- Mucus and bacteria also excreted in faeces
Urinary System
Main function: to maintain homeostasis by regulating volume & concentration of fluids by filtering and reabsorbing materials
from blood
Structure
Found in the abdominal cavity
- The right kidney is slightly lower than the left as it is pushed down by the larger right lobe of the liver
- The males urethra passes through the penis and carries urine & semen
- The female's urethra carries only urine through a separate opening in front of the vaginal opening
