Please enable JavaScript.
Coggle requires JavaScript to display documents.
12.3 The Human Kidney - Coggle Diagram
12.3 The Human Kidney
What are the functions of your kidney?
Your kidneys remove toxic urea from the body in your urine
Your kidneys also remove excess water and mineral ions not needed by the body
Your kidneys are important for homeostasis
If you don't drink a lot of water
Your kidneys conserve it
Very little urine is produced
The urine is very concentrated
Water is saved for use in the body
If you drink a lot of water
If you have too much water, your kidneys remove the excess
Lots of urine is produced
The urine is very dilute
Your kidneys remove excess mineral ions and excrete them in your urine.
How do your kidneys work?
Your kidneys filter out your blood
Glucose, mineral ions, urea, and water all move out of your blood into the kidney
Blood cells and proteins
Blood cells and large proteins are too big to be filtered out
They remain in the blood
Filtration
All blood passes through the kidneys about once every 5 minutes
Around 180 litres of water is filtered each day
About 99% is returned to the blood
Around 1800 cm³ of urine is produced each day
Urine is stored in the bladder
Selective reabsorption
All glucose is reabsorbed into the blood
Glucose is reabsorbed by diffusion and active transport
Water and mineral ions are reabsorbed depending on what the body needs
This is called selective reabsorption
Water balance
Water reabsorption is controlled by a feedback mechanism
Keeps the water balance of body fluids and cells within a narrow range
ADH and Water Balance
ADH
ADH is secreted by the pituitary gland
Controls the amount of water in the blood
Works through negative feedback
Receptor cells in the brain detect the concentration of solutes in the blood
Blood too concentrated / too little water
More ADH is released
Kidney tubules reabsorb more water
Small volume of concentrated urine produced
Blood concentration returns to normal
Blood too dilute / too much water
Less ADH is released
Kidney tubules reabsorb less water
Large volume of dilute urine produced
Blood concentration returns to normal
Kidney tubules
Selective reabsorption of water and mineral ions happens here