Excretion Flashcards
Excretion
the removal of waste products of metabolism from the body
egestion
the removal of undigested material from the gut
is egestion an example of excretion?
no
why do plants not have as great a need for excretion as animals?
because they make there own food (photosynthesis)
what do plants lose during the day?
oxygen and water vapour
through what are CO2, oxygen and water vapour excreted in the plant
the stomata and the lentils of the stem
what do plants lose at night?
CO2
what are lenticles
small pores in the stems
some carbon dioxide produced in photosynthesis
used in respiration by the plant
some carbon dioxide used in respiration
used in photosynthesis by the plant
where are waste products stored in the plant
in the vacuoles in the leaves
how do the plants get rid of the waste products
when the leaves fall off
meaning of homeostasis
staying the same
definition of homeostasis
the maintenance of a constant internal environment in an organism
2 roles of excretion in homeostasis
removing of waste products of metabolism from the body
control of water and salt balance in the body
osmoregulation
the maintenance of water and salt balance in body fluids
4 excretory organs in the human
kidneys
skin
lungs
liver
what do the kidneys excrete
water salts and urea
what does the skin excrete
water and salts in the form of sweat
what does the lung excrete
carbon dioxide and water
what does the liver excrete
bile pigments
what are bile pigments a product of
the breakdown of haemoglobin
urea
formed when excess amino acids are broken down in the liver
where are the kidneys located
in the abdominal cavity in the small of the back
2 functions of the kidney
excretion
osmoregulation
urine formed in
the kidneys
urine passes to bladder via
the ureters
urine released via
urethra
blood enters kidneys through
the real arteries
blood in renal arteries
high in waste products
what do the kidneys do to the blood
filter out waste and reabsorb useful materials
blood leaves kinky via
renal veins
blood in renal veins
purified blood
3 sections of kidney
cortex
medulla
pelvis
cortex
outer part of kidney
4 things in the cortex
glomeruli, Bowman’s capsule, distal and convoluted tubules
2 things in the medulla
loops of Henle and collecting ducts
Pelvis
the space int which the urine is collected from the collecting ducts
ureters
the tubes that carries the urine from the kidneys to the bladder
how many ureters do we have
2
nephron
functional unit of the kidney
nephrons are also called
kidney tubules
kidneys are made up of
millions of nephrons and their blood supply
nephrons carry out 2
excretion
osmoregulation
what does the great number of nephrons provide?
a large surface area for exchange of materials with the blood
blood flow in the kidneys
renal artery -> many afferent arterioles -> glomerulus -> efferent arteriole -> capillaries around the tubule -> venules -> renal vein
where is the glomerulus located
in bowman capsule
2 functions of kidney carried out by
the production of urine
composition of urine, water
96%
composition of urine, urea (nitrogen waste)
2.5%
composition of urine, salts
1.5%
3 processes in urine formation
Filtration of blood
Selective reabsorption
Secretion
Filtration of blood
small molecules are filtered out of blood leaving large ones behind
where does Filtration of blood occur
in the cortex
Selective reabsorption
as the filtrate flows along the tubule, useful substances are removed from it and taken back into the blood
where does Selective reabsorption occur
the cortex and the medulla
Secretion
some substances are actively transported by the cells of the nephron from the blood into the filtrate
2 examples of substances in secretion
H+ and K+
where does Secretion occur
the cortex
where do unwanted substances go?
flow from the kidney into the ureter and onto the bladder as urine
does Filtration occur under high or low pressure
high pressure
exact places of Filtration
through the glomerulus in bowman capsule
site of filtration
glomerulus
3 reasons why blood is under high pressure in the glomerulus
renal artery is branched off from the aorta, which is under high pressure from the heartbeat
efferent arteriole is much narrower than the afferent arteriole
arterioles present at both ends
what is the glomerulus
a network of capillaries which acts as a filter
1 feature of the glomerulus
has a large surface area
what does the high pressure in the glomerulus cause?
forces part of the blood plasma to leak through the one cell thick wall of the glomerulus into the lumen of bowmans capsule
liquid that comes out of the glomerulus
glomerular filtrate
cells of bowmans capsule
one cell thick
glomerular filtrate contains (6)
water salts urea glucose amino acids vitamins minerals
what do the substances in bowmans capsule all have in common
they are all very small, small enough to pass through bowman’s capsule
3 larger substances that cannot enter the glomerular filtrate
red and white blood cell
large plasma proteins
entering arteriole
afferent arteriole
exiting arteriole
efferent arteriole
what type of substances are reabsorbed into the blood
useful substances
what process is used in selective reabsorption
osmosis and active transport
how much glomerular filtrate is reabsorbed
99%
2 waste products not reabsorbed into blood
urea and uric acid
2 locations of selective reabsorption
proximal convoluted tubule
loop of henle
where does most reaborption take place
proximal convoluted tubule
how much water is rebsorbed by osmosis
80%
3 things reabsorbed by active transport (and some diffusion)
glucose, amino acids and vitamins
by what process is salt reabsorbed
active transport
4 ways the proximal convoluted tubule is adapted for reabsorption
thin walled
long
has microvilli
a lot of mitochondria
why is it important that the proximal convoluted tubule has a lot of mitochondria
to provide energy for active transport
how thin are the walls of the proximal convoluted tubule
1 cell thick
how long is the proximal convoluted tubule
14mm
function of microvilli in the proximal convoluted tubule
more surface area
what occurs in the descending loop of henle
H2O reabsorbed by osmosis
what occurs in the ascending loop of henle
salt reabsorbed by difussion near the bottom and active transport at the top
where does salt move out of during reabsorption
nephron
where does salt move into during reabsorption
the fluid of the medulla
what does the addition of salt do to the medulla
makes it more concentrated (low water conc.) than the fluid in the tubule (high water conc.)
what happens when the fluid of the medulla is more concentrated than the fluid in the tubule
water is removed from by osmosis from the descending loop of hence and the collecting duct
osmosis
the diffusion of water molecules across a semi-permeable membrane
down a concentration gradient
no energy needed (passive process)
what part of reabsorption happens in the distal convoluted tubule
the precise control of water and salt concentration in the blood
what controls the reabsorption of water into the blood
ADH
ADH
anti diuretic hormone
function of ADH
controls the osmoregulatory role of the kidney
what controls the reabsorption of salt into the blood
the hormone aldosterone
what part of reabsorption happens in the collecting duct
H2O can be reabsorbed by osmosis under the control of ADH
2 places where ADH acts
distal convoluted tubule
collecting duct
Where does selective secretion take place
in the distal convoluted tubule
what happens in selective secretion
some substances pass from the blood into the nephron e.g. drugs and H+ ions
what is the distal convoluted tubule important for?
adjusting the pH balance of the blood
the bladder
a sac with an elastic muscular wall that stores urine
what happens when urine starts to fill the bladder
it stretches the walls of the bladder
plasma
blood minus blood cells, liquid part of the blood
glomerular filtrate
filtrate made in bowman’s capsule, initially contains small molecules e.g. glucose and it travels through the nephron
urine
the liquid passing from the collecting ducts
2 ways in which glomerular filtrate differs from urine
has more water
contains useful molecules e.g..glucose that are not normally found in urine
other name for ADH
vasopressin
is concentration of urea higher in plasma or urine and why
urine because a lot of water gets reabsorbed out of it
H2O reabsorption in PCT
most
salt reabsorption in PCT
most
H2O reabsorption in descending limb of LoH
a little
salt reabsorption in descending limb of LoH
none
H2O reabsorption in ascending limb of LoH
none
salt reabsorption in ascending limb of LoH
a little
water reabsorption in DCT
some
salt reabsorption in DCT
some
water reabsorption in CD
some
salt reabsorption in CD
none
