Excretion Flashcards
Excretion
The removal of metabolic waste and excess and toxic materials
Excretory products of lungs
CO2 + water vapour
Excretory products of skin
Sweat (salt + water)
Excretory products of kidney
Urine (urea, water, ions)
Osmoregulation
Maintain a constant water concentration of the blood, brain and kidney
How can kidneys change osmoregulation
Depending on the ion and water concentration of the blood
Consequence of high water concentration of blood
Too much water (hypotonic)
Water enters cells by osmosis
Cells swell and burst
CELL LYSIS
Consequences of high salt concentration of blood
Too little water (hypertonic)
Water leaves cells by osmosis
Cells shrivel
CRENATION
Leaves excretory products
Day: oxygen
(Photosynthesis > respiration)
Night: CO2
(Respiration > photosynthesis)
Role of kidney
Filter blood and reabsorb useful substances back into the blood
Osmoregulation
Excretion
Ultrafiltration
Blood arrives at high pressure
Small molecules (water, urea, glucose + salts) are forced out of the blood into bowman’s capsule
Large molecules (protein + RBC’s) remain in blood
Selective réabsorption
All- glucose (diffusion + active transport)
Most- salts (diffusion)
Some- water (osmosis)
Convoluted tubules
What hormone controls water reabsorption
ADH- released from pituitary glands in the brain
What does ADH do
Low H2O conc -> more ADH -> increasing permeability -> more H20 reabsorbed
High H2O conc -> less ADH -> decreasing permeability-> less H2O reabsorbed
Why is protein not found in urine of a healthy person
Too large to pass through from the glomerulus into the bowman’s capsule
Why is glucose not found in the urine of a healthy person
All glucose Is reabsorbed back in the blood at the convoluted tubules
What is contained in urine
Urea, excess salt + water
Conc + volume of urine on a hot day
Sweat -> low H2O conc -> more ADH -> collecting duct more permeable -> more H2O reabsorbed -> more concentrated and less urine
Diabetes
Glucose in urine
Daily injections of hormone insulin
Urinary tract infection (UTI)
Protein in urine
Antibiotics
Renal failure
Protein and glucose in urine
Dialysis or kidney transplant
Glucose test
Benedict’s solution
Heat in boiling water bath for 5 mins
Blue -> brick red
Protein test
Biuret solution
Spotting tile
Blue -> lilac
Substances patients on dialysis need to remove from blood
Urea + mineral ions
They are toxic and otherwise the salt and water balance of your body is lost
Substances which are at the same conc in dialysis fluid and normal level in blood
Glucose + mineral ions
So they don’t lose these useful substance from the blood
Substances that dialysis fluid doesn’t contain at the start
Urea
So there is a strong conc gradient from blood to fluid for this substancr
Why is constant circulation of dialysis fluid important
So that the conc gradient is high so waste substances diffuse out
Kidney transplant advantages and disadvantages
Don’t have to follow a strict diet
Have to take medicine everyday of you life incase kidney is rejected
Dialysis advantage and disadvantages
It is more readily available than donor organs
Regular, long sessions connected to a dialysis machine
