functioning of the kidneys Flashcards
where does the blood in the capillaries of the glomerulus come from
from the afferent arteriole which is a branch of the renal artery
what does the blood in the capillaries of the glomerulus contain
1) water
2)salt
3) useful substances such as glucose , amino acids ,fatty acids and glycerol
4)waste substances such as urea an uric acids
5) and the normal constituents of blood ( blood plasma ,red and white blood corpuscles ,plasma proteins such a fibrinogen , albumin and globulin
how do some of these substances pass into the capsular space of bowman’s capsule
by glomerulus filtration
why is blood in the glomerulus under great pressure
because the afferent arteriole is wider than the efferent ar
what happens to the substances of the blood in the glomerulus as a result of the great pressure in the glomerulus
they are forced out through tiny pores on the capillary walls
the function of the podocytes , with slit pores between them
act as a selective filter allowing only fairly small particles to pass through
name the substances that are able to pass through the pores on the capillaries and slit pores on the podocytes
- water
- glucose
- amino acids
- urea
*uric acid - salts
what does not filter through
blood corpuscles and plasma protein
glomerulus filtrate
the liquid which is in the capsular space of bowmans capsule
what happens to the glomerulus filtrates
it passes down the renal tubule where reabsorption and tubular excretion occurs
what happens in the second capillary network
some water and almost all the glucose and other useful substances are selectively re absorbed by the second capillary network
dilute urine
the filtrate which enter the loop of Henle
function of the loop of henle
to ensure that the renal medulla always has a high concentration of sodium ions
where is the soduim ions pumped out of
it is pumped out of the loop of henle into the tissue fluid of the medulla
what does the pumped out sodium ions allow
this enables water to leave the ascending limb , distal convoluted tubule and collecting tubule by osmosis and enter the renal medulla i.e. water is conserved
what is the fluid in the collecting tubule
it is a highly concentrated urine
adh
a hormone that controls the actual amount of water re absorbed
function of the epithelium of the tubules
1) they absorb useful substances from the filtrate and passing them into the blood capillaries
2) excretes
what wastes do the epithelium of the tubule excretes
1) ammonia
2) creatinine
3) potassium , hydrogen , sodium and bicarbonate ions
4) certain drugs
what happens when blood is too acidic ( ph is too low )
1) more hydrogen ions are excreted from the blood into the renal tubule
2) more bicarbonate ions are reabsorbed into the blood
3) in this way the ph of the blood is increased until it becomes normal
what happens when the blood is too basic ( ph is too high )
less hydrogen ions are excreted from the blood into the renal tubule
2) less bicarbonate ions are re absorbed into the blood
3) in this way the ph of the blood is decreases until it becomes normal
what happens when there is a shortage of sodium in the blood
1) the adrenal cortex secrets more aldosterone
2) therefore more sodium is re absorbed by the blood capillaries at the distal and collecting tubules and less sodium ions are excreted
3) in this way the amount of sodium id raised until it comes back to normal
what happens when there is an excess of sodium ions in the blood
1) aldosterone secretion decreases
20 therefore the less sodium is re absorbed by the blood capillaries
3) this allows more sodium to be excreted
4) the amount of sodium in the blood is decreased until it gets back to normal
where is the urine temporarily stored
from the collecting tubules the urine passes into the renal pelvis and then down the ureters into the bladder where it is temporarily stored
urination
the process whereby from time to time the bladder is emptied by the urine passing along the urethra to the outside
what is urination as a result of
an involuntary and a voluntary process
involuntary process
the parasympathetic nerve fibers in the bladder wall cause the bladder to contract and the internal sphincter to relax
voluntary action
before urination can begin the external sphincter relaxes
what controls the voluntary action
under the command of the cerebrum , the brain therefore controls this action
