Excretion in Humans Flashcards
Topic 2 i. 2
many of the necessary metabolic reactions that take place in the cells of organisms produce
waste products
excretion is
the removal of metabolic waste products from the body
waste product found in the lungs
carbon dioxide
main roles of the kidney (2)
- removal of urea from blood
- adjustment of ion (salt) levels in the blood
waste product found in the skin
sweat
excretory products of the kidney
urea, ions and water
how do the kidneys carry out their main functions
by filtering stuff out of the blood under high pressure, and then reabsorbing the useful things.
what is the end product
urine
process of ultrafiltration
- blood from the renal artery flows through the glomerulus
- a high blood pressure squeezes water, urea and ions and glucose out of the blood and into the bowmans capsule
- the membranes between the bowmans capsule and the blood vessels act like filters so big molecules (proteins) and blood cells aren’t squeezed out and stay in the blood.
what is the filtered liquid called after ultrafiltration
glomerular filtrate
process of selective reabsorption
after the glomerular filtrate enters the bowmans capsule, glucose is the first substance to be reabsorbed at the proximal convoluted tube.
- all the glucose is reabsorbed from the proximal convoluted tubule so that it can be used in respiration. This happens through active transport
- sufficient ions are reabsorbed, not the excess ones
why is it called selective reabsorption
because only a selective few substances are reabsorbed
water reabsorption process
water is reabsorbed from the collecting duct in different amounts depending on how much water the body needs at a time
why is water reabsorption important/ needed
because the water is needed for osmoregulation
once out of the nephron where does urine go
nephron
through ureter
down to the bladder where it is stored
released by urethra
what is urea
a toxic waste product
where is urea produced
liver
what is urea made from
excess amino acids
what is osmoregulation
the process of maintaining water and salt concentrations across membranes within the body
why is osmoregulation important
maintaining water levels in the body is vital to prevent harmful changes occurring to cells of the body as a result of osmosis
what is one way that the body can balance the water coming in against the water going out?
by adjusting the amount of water that is excreted by the kidneys in the urine,
if a person is sweating a lot or hans’t drunk enough water, the kidneys can reabsorb more water so that less is lost in the urine and water balance is maintained
if body cells lose or gain too much water by osmosis what happens to them?
they do not function properly
what can too much water in the cells lead to
cells swelling as water moves into them, this has a diluting effect and can lead to cell lysis (bursting)
what can too little water in the cells lead to
cells lose water by osmosis as there is a too high concentration of ions and this has a dehydrating effect and can lead to cell death
where can water being lost be controlled and where can it not be controlled
cannot be controlled in the lungs or skin
can be controlled in the production of urine by the kidneys
what body part produces urea
liver
crenation
dehydrated cells
lysis
bursting of cells / excess water in cells
bowmans capsule does what
surrounds glomerulus
glomerulus is a
bundle of capillaries where ultrafiltration occurs
proximal convoluted tubule
selectively reabsorbs essential nutrients, ions, and a large amount of water back into the bloodstream.
collecting duct
end part of nephron where urine collects
loop of henle
vital component for maintenance of water balance
why is excretion so important
because a build up of waste products can be harmful to cells
what effect could waste have on cells (2)
- toxic - denature their enzymes
- osmotic
what is the osmotic effect that waste could have in cells
when in high concentrations, tissue fluid can become more concentrted, drawing water out of cells which can prevent the cells from functioning properly
it uses up storage place within cells which should be saved for useful molecules not waste products
excretory organs of the human body
skin
kidneys
lungs
liver
where do metabolic reactions take place
in every cell of a living organism
what are the 2 sources of water in the body
- water produced as a result of aerobic respiration
- water in the diet
2 ways water is lost
Via the lungs during exhalation (breathing out)
Lost from the skin as sweat (along side mineral ions and urea)
2 key functions of the urinary system
- filter and remove waste products
- control water levels
the aorta branches to form what artery
renal artery
what does the renal artery deliver
oxygenated blood to the kidneys
de-oxygenated blood will exit the kidneys through the
renal vein
three regions of the kidney
- cortex (outermost layer)
- medulla (inner section)
- renal pelvis
what is the renal pelvis
tube that links kidney to ureter
will blood in the renal vein contain waste products and why
NO because they will have been filtered out by the kidney
what parts of the kidney would be found in the cortex
glomerulus & bowmans capsule
proximal convoluted tubule
distal convoluted tubule
collecting duct
what part of the kidney holds the loop of henle
medulla
how is blood pressure increased in the glomerulus
narrowing of cappilaries
for ultrafiltration to happen, should the blood pressure be high or low
high
glucose is reabsorbed by
active transport
cells in the proximal convoluted tubule contain many
mitochondria as glucose is absorbed by active transport and thats an active process
necessary salts are absorbed back into the blood by ___ and ____ in the ___ __ ___
diffusion and active transport
loop of henle
as salts are absorbed back into the blood, ___ follows by ___
water
osmosis
what is ADH
anti-diuretic hormone
what does ADH make the collecting duct become
more permeable so more water is reabsorbed back into the fluid
what does the brain tell the _____to release according to __
- pituitary gland
- ADH
- according to how much is needed in the blood
any change in water levels in the blood are detected by the ______ which then sends a signal to the ____
hypothalamus
pituitary gland
what produces ADH
pituitary gland
if water content is too high …
- The pituitary gland releases less ADH which leads to less water being reabsorbed in the collecting ducts of the kidney by osmosis (the collecting ducts become less permeable to water)
- As a result, the kidneys produce a large volume of dilute urine
if water content is too low
- The pituitary gland releases more ADH which leads to more water being reabsorbed in the collecting ducts of the kidney by osmosis (the collecting ducts become more permeable to water)
- As a result, the kidneys produce a small volume of concentrated urine
How much ADH is released depends on
how much water the kidneys need to reabsorb from the filtrate
urine contains a mixture of
urea
excess mineral ions
excess water
large quantities of urine are usually what colour and why
pale yellow
because it contains a lot of water and so the urea is less concentrated
small quantities of urine are usually what colour and why
darker yellow
because it contains little water and so the urea is more concentrated
why will concentration of urine change (3)
water intake
temperature
exercise
how does water intake affect the concentration of urine
the more fluids drunk, the more water will be removed from the body and so a large quantity of pale yellow, dilute urine will be produced
how does temperature affect the concentration of urine
the higher the temperature the more water is lost in sweat and so less will appear in the urine, meaning a smaller quantity of dark yellow, concentrated urine will be produced
how does exercise affect the concentration of urine
the greater the level of exercise, the more water is lost in sweat and so less will appear in the urine, meaning a smaller quantity of dark yellow, concentrated urine will be produced
what does the bladder do
collects urine, holds it
