Excretion Basics
Define excretion.
The removal of metabolic waste products from the body.
What is the main excretory product of the lungs?
Carbon dioxide (and some water vapour).
Which organ removes carbon dioxide?
The lungs
Name the main organs of the urinary system.
Kidneys, ureters, bladder, urethra.
Where does ultrafiltration, which involves filtering blood under high pressure, take place
In the glomerulus/Bowman’s capsule
How does excretion differ from egestion?
Excretion = removal of metabolic wastes (e.g. urea, CO₂);
Egestion = removal of undigested food from the digestive tract.
State two nitrogenous waste products.
Urea, uric acid, creatinine, ammonia (any two).
Which organ regulates water and salt balance in the body?
The kidneys
Which tube carries urine from the kidney to the bladder?
Ureter
Define osmoregulation.
The control of water and solute concentration in the body to maintain a constant internal environment.
Name two excretory products in humans.
Carbon dioxide, urea, water, salts (any two).
Which excretory product is formed when excess amino acids are broken down in the liver?
Urea
State one excretory function of the skin.
Removes water, salts, and small amounts of urea via sweat.
What is the role of the renal artery?
Carries oxygenated blood rich in wastes to the kidney for filtration.
A person’s urine sample is tested and found to contain glucose. What condition might this indicate?
Diabetes mellitus
Why is excretion important for homeostasis?
Prevents toxic buildup of wastes; maintains internal balance of water, salts, pH, etc.
Name one excretory product in plants and how it is removed.
Oxygen (photosynthesis) → diffuses out through stomata;
Carbon dioxide (respiration) → diffuses out;
Other wastes (alkaloids, tannins, resins) → stored in leaves/bark which are shed.
Explain why the liver is considered an excretory organ.
It breaks down excess amino acids (deamination) producing urea; also detoxifies harmful substances.
Outline one structural adaptation of the kidney for its function.
Millions of nephrons → large surface area for filtration;
Close association of capillaries with tubules → efficient exchange;
Highly folded tubules → increases reabsorption efficiency
Daily Double!!
Explain how sweating helps to maintain homeostasis.
Removes excess heat as sweat evaporates, cooling the body; also excretes small amounts of salts and urea.