2.10 Excretion Flashcards
What is excretion?
the removal of metabolic waste from the body
What are the two most significant toxic compounds?
carbon dioxide - dissolves to form a weakly acidic solution in blood and tissue fluid
urea - comes from excess amino acids and can denature enzymes
Describe Ultrafiltration
- occurs between the Glomerulus and Bowmans capsule
- has a high blood pressure because the vessel going in is lager then the vessel going out
- capillaries have pores which allow small molecules to be forced to the Bowmans capsule
- salts, amino acids, urea, water and glucose form the filtrate inside the nephron
- proteins, red blood cells, white blood cells and platelets are left behind
Describe Selective reabsorption
Returns all the useful molecules to the blood
- ALL glucose
- ALL amino acids
- most H2O
Happens via diffusion, active transport and osmosis
The micro villi infolding of cell membrane increase the surface area and the mitochondria respire providing ATP for active transport
What happens in the Loop of Henle?
The medulla becomes salt lowering the water potential causing water to diffuse out of the blood via osmosis
Where is urea formed?
liver
Urea is formed from the breakdown of which biological molecule?
ammonia
Where is urea excreted from the body?
the kidney
Which blood vessel carries oxygenated blood to the kidneys?
renal artery
Which tube carries urine from the kidney to the bladder?
ureter
Where does ultrafiltration occur in the nephron?
between the glomerulus and the bowman’s capsule
Where does selective reabsorption occur in the nephron?
Loop of Henle
What molecules are reabsorbed during selective reabsorption?
all glucose
all amino acids
most water
What transport process occurs to reabsorb glucose?
active transport
How are the cells specialised for a fast rate of diffusion?
cells lining the PCT are specialised for movement of molecules
They have a folded membrane to increase the surface area
How are the cells specialised for a fast rate of active transport?
lots of mitochondria
Site of aerobic respiration, therefore produces large amounts of ATP needed for active transport
Where does concentration of the filtrate occur?
Loop of Henle
How does the Loop of Henle concentrate the urine?
The Loop of Henle concentrates the urine by transporting salt into the blood by active transport
What is meant by the term osmoregulation?
Maintenance of the water concentration of the body
Explain how changes in the composition of urine are brought about when a person is dehydrated (short of water).
high blood concentration
hypothalamus/Osmoreceptors
Pituitary gland
More ADH
Collecting duct
More permeable
More water reabsorbed into blood
Less water in urine
Why must dialysis contain purified water, glucose and mineral ions?
cell require water for water balance
glucose is needed for respiration/energy
Explain why a person with severe kidney disease will need dialysis to continue for life.
body produces metabolic waste
which needs to be excreted
kidneys cannot recover, until a transplant
What is meant by a partially permeable membrane?
only certain types of products are allowed to pass through the membrane
does not let larger ones pass through
