Excretion Flashcards
What is excretion?
The removal of toxic waste substances which have been made by cells
What is egestion?
The removal of faeces from the body
Why do excess amino acids need to be broken down?
Humans cannot store excess amino acids (unlike with carbohydrates and lipids)
Why do amino acids need to be removed from the body?
Because what they are broken down into is toxic
Where is urea made?
Liver cells
What are the 3 main sections of the kidney called?
cortex, medulla and pelvis
What is the job of the nephron?
To filter the blood
What is the job of the kidney?
filters the blood + removes any excess materials and passes them to the bladder to be excreted
Is the size of the artery at the exit of the glomerulus bigger or smaller than at the entrance, and what effect does this have?
Smaller at the exit, causes a build-up of pressure
What is the effect of the pressure in the glomerulus?
Forces small molecules (urea, glucose, water and salt) across into the Bowman’s capsule
What is the solution in the Bowman’s capsule called?
Glomerular filtrate
What happens to larger molecules during ultrafiltration?
Too big to pass through cell membrane, stay in the blood
What is the job of the proximal convoluted tubule?
To reabsorb glucose and salt - creates an osmotic potential (80% water)
State the pressure of the blood from the renal artery
High pressure - helps push things out of the blood
How much water is reabsorbed in the loop of Henlé?
5%
How does the loop of Henlé aid water reabsorption?
Makes the medulla salty
By what processes are water and salts reabsorbed?
Osmosis and active transport
What detects a change in water potential?
Hypothalamus
What does the hypothalamus stimulate during osmoregulation?
Signals pituitary gland to release different amounts of ADH
What is the amount of ADH released detected by?
Collecting duct
If there is a high water potential, how much ADH will be released?
Less ADH released by pituitary gland
If there is less ADH released, what will happen to the collecting duct?
Will make themselves impermeable to water so less water is absorbed into blood
If there is a high water potential, what will eventually happen to the urine?
A larger volume of dilute urine is produced; water potential falls
How is the PCT involved in selective reabsorption?
All proteins and + amino acids are selectively reabsorbed in the PCT, using diffusion & active transport
