excretion ! Flashcards
catabolic reactions !
chemical reactions whereby complex substances are broken down into simpler ones
anabolic reactions !
chemical reactions which simpler substances are built up into more complex substances
excretion !
process by which metabolic waste products & toxic substances are removed from the body
need for excretion !
metabolism : produces waste products (CO2, H20, urea) that can harm the body when accumulated
therefore -> need to be removed by excretion
excreted by…
skin : sweat
- excess mineral salts + nitrogenous waste products (urea) + excess water
lungs : expired air
- CO2 + water vapour
liver : faeces from intestines
- bile pigments
kidney : urine
- urea + excess H20 + excess salts
urinary system !
kidneys ureters urinary bladder urethra sphincter muscle
kidneys function !
remove waste products (excess H20, urea, mineral salts) from blood by urine
ureters function !
connects kidneys to bladder
carries urine to bladder
urinary bladder function !
stores urine temporarily
urethra function !
passage to discharge urine from urinary bladder
sphincter muscle function !
controls exit of urine from the urinary bladder
when urinary bladder is full : sensory neurones send nerve impulses to brain
brain : send nerve impulses to sphincter muscle to relax
- urine : flow into urethra & out of the body
kidney tubules !
narrow
richly supplied with blood vessles : absorb water, nutrients & mineral salts needed
urine formed
nephron !
basic functional unit of kidneys
richly supplied with blood capillaries
nephron flow of blood !
renal artery -> afferent arteriole -> efferent arteriole -> glomerulus -> blood capillaries -> renal vein
nephron structure !
Bowman’s capusule
glomerulus : dense network of capillaries contained in Bowman’s capsule
proximal convoluted tubule
loop of henlé
urine formation !
ultra-filtration
selective reabosrption
ultrafiltration !
blood passes from branches of renal artery -> glomerulus
caused by high blood pressure generated
- afferent ateriole’s lumen is larger than efferent ateriole -> more blood enters glomerulus than blood leaving -> high pressure -> substances to be forced out of blood
basement membrane around the glomerulus : fine filter
- partially permeable membrane : allowing only small molecules (glucose, amino acids, mineral salts & nitrogenous wastes) can pass through to form filtrate
blood cells, platelets & large molecules (proteins & fats) : remain in the glomerular capillaries
ultrafiltration filtrate flow !
PCT -> loop of henlé -> DCT -> collecting duct
ultrafiltration non-filtrate flow !
efferent atery -> blood capillaries -> renal vein
selective reabsorption !
allows useful susbtances to be reabsorbed back into blood capillaries
- glucose, amino acids, salts : diffusion & active transport
- water : osmosis
loop of Henlé : some water reabsorbed into bloodstream from filtrate in tubule
DCT : some salts reabsorbed
collecting duct : water reabsorbed
osmoregulation !
process whereby amount of water & solute concentrations in blood are controlled to maintain constant water potential in the body
ADH
controls water potential of blood plasma
- produced by hypothalamus
- released by pituitary gland
- increases permeability of water of the collecting duct
importance of constant water potential of blood plasma
if too concentrated : RBC -> dehydrate -> crenated
if too dilute : RBC -> absorb water -> expand -> burst
excess water in blood
large intake of water : water potential in blood plasma increases
stimulates hypothalamus in brain -> pituitary gland secretes less ADH into blood stream
cells in walls of collecting ducts become less permeable to water -> kidney tubules reabsorb lesser water
larger volume of urine produced (more diluted) -> water potential of blood plasma returns to normal level
dehydration
loss of water : water potential in blood plasma decreases
stimulates hypothalamus in brain -> pituitary gland secretes more ADH into blood stream
cells in walls of collecting ducts become more permeable to water -> kidney tubules reabsorb more water
smaller volume of urine production (more concentrated) -> water potential of blood plasma returns to normal level
kidney failure !
high blood pressure diabetes alcohol abuse severe accidents that physically damage kidney complications from major surgery
dialysis machine !
mimics function of kidney
- blood is drawn from vein in patient’s arm
- blood is pumped into dialysis machine through a tubing
- tubing : bathed in dialysis fluid & its walls are partially permeable
- small molecules (urea & metabolic waste products) : diffuse out of tubing
- larger molecules (platelets & blood cells) : remain in tubing
- filtered blood is released to a vein in patient’s arm
dialysis tubing !
walls are partially permeable
- allows only small molecules (urea) to diffuse out of tubing from bloodstrream
- big molecules (proteins, blood cells) : remain in tubing
narrow, long, coiled
- increases surface area to volume ratio -> speeds up rate of exchange of substances between blood & dialysis fluid
- provides sufficient time for exchange of substances
direction of blood flow : opposite to flow of dialysis fluid
- maintains diffusion gradient for removal of waste products
dialysis fluid !
contains essential salts for body
- ensures that these salts do need diffuse of out blood through tubing to dialysis fluid
- if blood lacks these salts : salts in dialysis fluid can diffuse into blood
concentration of glucose & amino acids are the same as bloodstream
- prevents glucose & amino acids in blood to diffuse out of blood into dialysis fluid
- if blood lacks glucose & amino acids, they can enter bloodstream from dialysis fluid
does not contain nitrogenous waste products (urea)
- creates diffusion gradient between dialysis fluid & blood -> allows for nitrogenous waste products (urea) to diffuse out of blood into dialysis fluid
