excretory system Flashcards
what is excretion
removal of the waste product of metabolism, and substances in excess of requirements from the body.
why must carbon dioxide be excreted
Carbon dioxide must be excreted as it dissolves in water easily to form an acidic solution which can lower the pH of cells. which reduces activity of enzymes
what is the process of breaking down excess amino acids called
deanimation
how does the liver split up the amino acid
carbon is turned into glycogen
nitrogen is turned into ammonia (highly toxic) so converted to urea which is less toxic
where does the urea go
The urea dissolves in the blood and is taken to the kidney to be excreted
A small amount is also excreted in sweat
what do the lungs excrete
carbon dioxide
what is the main blood vessel that brings blood into the kidneys
renal artery
what is the main blood vessel that brings blood out of the kidney
renal vein
what carries urine from the kidney to the bladder
ureter
what are the waste substances that need to be removed from the blood
creatinine
urea
excess hormones
excess water
ammonia
uric acid
salts
in the kidney which structures help transport glucose
artery, vein
summarise the livers main 4 roles
assimilation of amino acids to form proteins
break down of the nitrogen containing parts of excess amino acids
forms urea which is excreted by the kidneys
breakdown of red blood cells
what is urine
mineral salts and urea dissolved in water
what is the urine pathway
Liver (urea) –> kidney –> ureter (urine) –> bladder –> urethera
temperature and exercise affect on volume and concentration of urine
temperature and exercise increase leads to increased dehydration and hence less volume and more concentrated urine as water content will be less.
high hydration means…
more volume and less concentrated urine
how does temperature and exercise increase dehydration
as temperature and exercise increase, more sweat is released causing the body to lose water and salts through sweat
what are the kidney’s function in the body
regulate the water content in the blood (vital for maintaining blood pressure)
excrete toxic waste products of metabolism
what is a nehpron
nephron acts as a filterate in the kidney and is the functional unit of the kidney
where is glucose reabsorbed in the nephron
proximal convuluted tube
where is urea reabsorbed in the nephron
not absorbed, excreted through urine
where are salts reabsorbed in the nephron
loop of henle
where is water reabsorbed
loop of henle
collecting duct
why does ultrafiltration take place
capilaries get narrower as they go further into the glomerulus which increases the pressure of the blood in the vessels
this causes the smaller molecules in the blood to be forced out of the capilaries and into the bowmans capsule
how is glucose reabosrbed
through active transport in the proximal convuluted tube
how are salts reabsorbed
through diffusion in the loop of henle
how is water reabsorbed
through osmosis in the distal convuluted tube
where is urine formed
in the collecting duct
how is the nephron adapted to its function
the nephron reabsorbs glucose through active transport, has many mitochondria to provide energy for the glucose moleucules to move against the concentration gradient
in a normal patient which structures transports glucose
renal artery
renal vein
if both kidneys are damaged what are the consequences
build-up of toxic wastes in the body which will be fatal if not removed
what happens if no treatment is done for both kidneys being damaged
toxins such as urea build up and salt and water balance is upset
causing death
what is kidney dialysis
artificial machines carry out the functions of the kidney outside the body
what is kidney transplant
one healthy kidney from a willing donor will replace the 2 diseased kidneys
how do kidney dialysis machines work
Patients are connected to a dialysis machine which acts as an artificial kidney to remove most of the urea and restore/maintain the water and salt balance of the blood
dialysis fluid contains same conc of salts, water and glucose, hence only excess or some of the salts/water/glucose is filtered out. no urea conc so all urea diffuses out
how is blood transported in a kidney dialysis machine
Unfiltered blood is taken from an artery in the arm, pumped into the dialysis machine and then returned to a vein in the arm
how does the dialysis machine work inside the machine
Inside the machine the blood and dialysis fluid are separated by a partially permeable membrane
- the blood flows in the opposite direction to dialysis fluid, allowing exchange to occur between the two where a concentration gradient existsw
what is dialysis fluid made up of
Dialysis fluid contains:
-a glucose concentration similar to a normal level in blood
-a concentration of salts similar to a normal level in blood
-no urea
how does the dialysis glucose concentration and the human body’s blood glucose concentration interact with eachother
As the dialysis fluid contains a glucose concentration equal to a normal blood sugar level, this prevents the net movement of glucose across the membrane as no concentration gradient exists
how does the dialysis urea conc and the urea conc in the blood interact with eachother
As the dialysis fluid has no urea in it, there is a large concentration gradient - meaning that urea diffuses across the partially permeable membrane, from the blood to the dialysis fluid.
how does the dialysis salt conc and the blood salt conc interact with each other
As the dialysis fluid contains a salt concentration similar to the ideal blood concentration, movement of salts across the membrane only occurs where there is an imbalance (if the blood is too low in salts, they will diffuse into the blood; if the blood is too high in salts, they will diffuse out of the blood)
what is an additive of the dialysis solution
An anticoagulant is added to blood before it runs through the machine to prevent the blood from clotting and slowing the flow
what happens to urine after exiting the collecting chamber
goes into ureter through peristalsis then stored in bladder then excreted through unrinary system
describe the functions of the liver in excretion
deamination
excess amino acids, converted to ammonia which is then quickly converted to urea as ammonia is highly toxic
1 adv and 1 disadv of kidney transplant compared to dialysis
ADV: patients do not need to return to clinic for dialysis
DISADV: need immunosuppressant drugs
explain the function of the renal capsule
ultrafiltration
high blood pressure assists filtrate to pass through
glomerulus
filtrate small enough to move through the glomerulus
filtrate contains dissolved salts, urea and glucose
where is urea formed
liver
what is the function of the proximal convoluted tube
selective reabsorption
back into the blood
e.g glucose
what is the function of the glomerulus
ultrafiltration
small molecules from blood
are pushed out under high pressure
why might the concentration of sodium ions be higher in the liquid that flows out of the liver than the concentration in urine
water has been reabsorbed by osmosis
in collecting duct
more water makes the liquid dilute, hence less water will make the liquid concentrated
name two components of the blood that is not in dialysis fluid
red blood cells
white blood cells
Amino acids are processed by the liver. describe the process
deanimation
nitrogen component of amino acids are converted to ammonia
quickly converted to urea
as ammonia is too toxic and can be harmful
carbon component of amino acids are converted to glucose.
Some amino acids are used to make protiens (eg fibrinogen)
how does excretion differ in diabetic patients
when the glucose concentration in blood becomes too high
all the glucose isnt able to be reabsorbed in the PCT
glucose has a strong osmolarity and pulls water with it
causing patients to pee excessively and lose a lot of water
what does the glomerulus do
ultrafilteration
small molecules are forced out from blood into glomerulus due to high pressure
large molecules don’t pass
what does the proximal convoluted tubule do
selective reabsorption
back into blood
eg glucose
