Excretion Flashcards
Excretion
the removal of waste products of metabolism from the body
3 organs of excretion
lungs
skin
kidneys
2 things the lungs excrete
CO2 H2O
2 things the skin excretes
H2O, NaCl
4 things the kidneys excrete
H2O, excess salts, urea, uric acid
where are the kidneys located
in the abdominal cavity in the small of the back
2 functions of the kidneys
excretion
osmoregulation
excretory function of the kidneys
removal pf urea, uric acid, salts and water
osmoregulatory function of the kidney
maintenance of water and salt balance in body fluids
urine path
formed in kidneys, ureter to bladder, released from urethra
each kidney consists of
many tiny tubes called nephrons and blood capillaries
function of nephrons
provide a large surface area for exchange of materials with blood
blood through kindey
renal artery - afferent arteriole - glomerulus - efferent arteriole - capillaries - venule - renal vein
function of kidney
to remove unwanted substances from the blood, this results in the formation of urine
3 processes involved in urine formation
filtration of blood
selective reabsorption
secretion
filtration
small molecules are filtered out of the blood
location in kidney of filtration
cortex
selective reabsorption
as the filtrate flows along the tubules, useful substances are removed from it and taken back to blood
location in kidney of selective reabsorption
cortex and medulla
secretion
some substances e.g K+ and H+ not needed by the body are actively transported by the cells of the nephron from the blood into the filtrate
location in kidney of secretion
cortex
filtration is under
high pressure
3 ways that the blood in the glomerulus is put under pressure
arterial blood pumped from heart
arterioles present at both ends
afferent arteriole has a wider lumen than efferent arteriole
what comes out of glomerulus
glomerular filtrate
3 things not in glomerular filtrate
red and white blood cells, platelets and blood proteins
glomerular filtrate
part of the blood plasma that passes through the glomerulus into the lumen of Bowman’s Capsule
Selective reabsorption
useful substances are taken back from the glomerular filtrate by osmosis and active transport and returned to the blood
4 locations of reabsorption in the nephron
proximal convoluted tubule
loop of Henle
Distal convoluted tubule
Collecting duct
3 things reabsorbed in proximal convoluted tubule
water (osmosis)
glucose and amino acids (active transport)
salt (active transport)
2 things reabsorbed in loop of Henle
H2O (osmosis)
salts (active transport)
1 thing reabsorbed in distal convoluted tubule
H2O (osmosis)
controlled by ADH
1 thing reabsorbed in collecting duct
H2O (osmosis)
controlled by ADH
what is the filtrate called after selective reabsorption
urine
why is the concentration of urea and uric acid much higher in urine than in plasma/glomerular filtrate
a lot of H2O is reabsorbed from filtrate as it moves along the tubule
the bladder
a sac with an elastic muscular wall that stores urine
composition of urine
urea uric acid salts water (hormones, vitamins, drugs etc)
ADH 2 names
anti-diuretic hormone
vassopressin
what secretes ADH
pituitary gland
function of ADH
makes the cells in the distal convoluted tubule and collecting duct more permeable to water
what is amount of ADH secreted controlled by?
water concentration of the blood
homeostasis
the maintenance of a constant internal environment in the body
why is homeostasis necessary
to ensure that cells have optimum conditions to carry out their metabolism
role of kidney in homeostasis
osmoregulation
osmoregulation in kidney
excretion/reabsorption of water
excretion/reabsorption of salts
1 disorder of the urinary system
kidney failure
treatment for kidney failure
dialysis / kidney transplant
