kidney Flashcards
2.71 what are the excretory products of the lungs, kidneys and skin (organs of excretion)
lungs via blood plasma - carbon dioxide, made in respiring cells, made by respiration
kidneys & skin - urea, made in liver cells, made by breakdown of amino acids (deamination)
2.72B how does the kidney carry out its roles of excretion?
- urea has been produced by liver, must be removed by another organ (kidney)
- kidney filters blood & removes any excess material and passes them to bladder to be excreted
- kidney contains millions of tiny structures called nephrons, these are the structures that filter the blood
2.75B describe ultrafiltration in the bowman’s capsule and the composition of the glomerular filtrate
- diameter of efferent arteriole at exit of glomerulus smaller than diameter of afferent arteriole at entrance. this creates a build up of pressure in capillaries forming the glomerulus
- this pressure forces small molecules (urea, glucose, amino acids, salts) out of capillaries of glomerulus & into Bowman’s capsule. this forms the glomerular filtrate
- larger molecules (proteins, red blood cells) too big to fit across capillary walls so stay in blood
- capillaries of glomerulus have gaps between cells, the basement membrane surrounding the capillaries controls which molecules can pass into Bowman’s Capsule
2.74B describe the structure of a nephron
nephron is made up of a kidney tubule which has several sections:
- Bowman’s capsule
- proximal convoluted tubule
- Loop of Henlé
- distal convoluted tubule
- collecting duct
surrounding the tubule is a network of capillaries with a knotted section which sits inside Bowman’s capsule
2.77B why does selective reabsorption of glucose occur at the proximal convoluted tubule?
- filtrate travels to PCT, however it contains lot of useful materials such as glucose which would be wasted unless recovered
- specialised cells within walls of PCT, these move useful materials back into blood stream
- initially molecules move by diffusion, but some substances also moved against concentration gradient using ATP (active transport).
2.79B what does urine contain?
water, urea, ions
what is excretion?
the removal of toxic waste substances which have been made by cells
what’s egestion?
the passing of undigested food as faeces through the anus
where is urea formed?
liver cells
how is urea made?
breakdown of amino acids (deamination)
where’s urea excreted from?
the kidneys and skin
which blood vessel carries oxygenated blood to the kidneys?
renal artery
which tube carries urine from the kidney to the bladder?
the ureter
go onto the summer work thing 2024 and try re-doing the diagram for the nephron’s labels
ok
where does ultrafiltration occur in the nephron?
the glomerulus
why do small molecules move from the capillaries of the glomerulus into the bowman’s capsule (forming the glomerular filtrate)?
- ultrafiltration
- build up of pressure in capillaries forming glomerulus (caused by efferent arteriole’s diameter < afferent arteriole’s diameter) forces them into Bowman’s capsule
why’s there high pressure in the glomerulus?
- diameter of efferent arteriole (exit of glomerulus) «_space;diameter of afferent arteriole (entrance)
- creates build up of pressure in capillaries forming glomerulus
why is there no protein in the urine of a healthy person?
because larger molecules like protein or red blood cells are too big to fit through capillary walls, so stay in blood
where does selective reabsorption occur in the nephron?
the proximal convoluted tubule (pct)
what molecules are reabsorbed?
- all glucose, amino acids
- some salts
- 80% of water
what transport processes occur to reabsorb glucose & amino acids (selective reabsorption)
active transport
also filtrate —> blood
what transport processes occur to reabsorb water (selective reabsorption)
osmosis
also filtrate —> blood
what transport processes occur to move harmful substances from blood to filtrate (selective reabsorption)
active transport
what transport processes occur to filter ions from filtrate into blood (selective reabsorption)
active transport
how are the cells in the PCT specialised for a fast rate of diffusion?
- folded membrane to increase surface area
how are the cells in the PCT specialised for a fast rate of active transport?
they have many mitochondria to provide ATP for active transport
where does concentration of the filtrate occur? (water reabsorption)
the loop of henle
how does the loop of henle concentrate the urine?
- transports salt into blood by active transport
- this causes water to diffuse into blood by osmosis
where does osmoregulation occur in the nephron?
the collecting duct
what part of the brain detects the water concentration of the blood?
the hypothalamus
2.78B if the blood is too concentrated, is more or less ADH released?
more - the blood doesn’t have enough water
2.78B which part of the brain releases ADH?
the pituitary gland
2.76B and kind of 2.78B what effect does ADH have on the collecting duct (cd)?
- ADH is hormone, so carried in the blood
- cd surrounded by capillaries
- ADH diffuses out of blood, binds with receptors on surface of cd cells
- if ADH binds, this triggers wall of cd to become more permeable to water
2.78B if there’s a high concentration of ADH in the blood, what’ll happen to urine production?
less urine will be produced; it’ll be more concentrated & darker in colour
what is meant by the term osmoregulation?
osmoregulation is the regulation of water levels within the body to keep it rising or falling too much
how can water levels be changed? (osmoregulation)
by adjusting the permeability of the collecting duct in the nephron
describe urea formation
- amino acids filtered into liver, along w rest of blood via hepatic artery & hepatic portal vein
- excess amino acids can’t be stored & need to be broken down so they can be excreted. they’re broken down into carbs and ammonia
- ammonia very toxic, must
be converted into slightly less toxic chemical (urea) - amino acids that are needed + the urea are released back into blood stream via hepatic vein
what are the three main sections of the kidney?
- around outside, lighter colour: cortex
- in middle are triangular shaped medulla
- in centre is the pelvis
(also contains millions of tiny structures, nephrons)
