Lab9 Flashcards
what are the 3 main processes that nephrons use to form urine?
filtration, reabsorption, secretion
where does secretion occur?
can occur at different places along the length of the tubule and collecting duct.
(like reabsorption)
the process by which important nutrients such as glucose, amino acids, and ions are removed from the filtrate an returned to the blood is called:
reabsorption
reabsorption moves substances from the ____ in the kidney and returns them to the blood in the ____. or _______
tubule
peritubular capillaries or vasa recta
what percent of the filtrate is reabsorbed?
99%
everything is filtered except…
blood vessels and plasma
what is the process in which drugs, ammonia, and H+ (hydrogen ion) are taken from the blood and put into the kidney tubule (filtrate) so that they can be eliminated from the body?
secretion
T/F
the urine that is eventually excreted from the kidneys has the exact same substances as the filtrates that was formed in the filtration process except that water is removed in the. nephron in order to concentrate urine.
false.
different from original filtrate because of reabsorption and secretion.
what is not excreted in urine?
glucose
filtration happens at
the glomerulus:
a ball of fenestrated capillaries located in capsule.
between the foot processes of the podocytes
filtration slits
wall of glomerulus
basal lamina
endothelial capillary wall
foot processes of podocyte
what forms the filtration membrane
basil lamina
fenestrated capillary wall
filtration slits
what forms the filtration membrane
basil lamina
fenestrated capillary wall
filtration slits
filtration is selective based on …
particle size
which of the following is not a component of the filtration membrane?
a. fenestrated glomerular capillaries
b. basal lamina
c. podocyte filtration slits
d. parietal epithelial cells of the glomerular capsule
d. parietal epithelial cells of the glomerular capsule
which of the following solutes are not able to pass through the filtration membrane in a healthy kidney?
a. amino acids
b. sodium ions
c. plasma proteins such as albumin
d. glucose
c. plasma proteins such as albumin
Proteinuria:
condition - proteins is observed in the urine.
damage to the filtration membrane and could be due to sever hypertension, heart failure, and renal disease
filtration slits are formed by the interdigitating processes of which type of cell?
podocytes
podocytes:
the cells that form the visceral layer of Bowmans capsule.
have cytoplasmic extensions that wrap around the outer surface of the glomerular capillaries.
cytoplasmic extensions have foot processes the interdigitate with each other and form spaces called filtration slits.
what is the name of the cell indicated
podocyte
filtration takes place at?
A. glomerulus.
what force fuels filtration?
hydrostatic forces:
outward: hydrostatic pressure in glomerular capsules (HPgc)
inwards: hydrostatic pressure in the capsular space (HPcs) and colloid osmotic pressure in glomerular capsules (OPgc)
hydrostatic forces force fluids and solutes through a porous membrane that is composed of three layers:
- fenestrated endothelium of the glomerular capillaries
- basement membrane
- filtration slits between the foot processes (pedicels) of podocytes
the hydrostatic pressure in glomerular capillaries (GHP or HPgc) is essentially
glomerular blood pressure
the chief outward force pushing water and solutes out of the blood and across the filtration membrane is
hydrostatic pressure in glomerular capillaries (GHP or HPgc)
the blood pressure in the glomerulues is ______ compared to other capillaries
extremely high
the inward forces inhibit filtrate formation by opposing HPgc. these forces are:
- hydrostatic pressure in the capsular space (HGcs)
- glomerular colloid osmotic pressure (OPgc)
hydrostatic pressure in the capsular space (HPcs):
the pressure exerted by the filtrate already in the glomerular capsule.
CHP is much higher than the hydrostatic pressure surrounding most capillaries because
filtrate is confined to a smaller space (inside of the capsule) with only a narrow outlet (the first part of the proximal convoluted tubule)
glomerular colloid osmotic pressure (OPgc):
the pressure exerted by the proteins in the blood in the glomerular capillaries
pulls fluids back into capillary
the measure of filtration.
Glomerular Filtration Rate (GFR):
*[the amount of filtrate that is produced by both kidneys in one minute.]
tells us whether the kidneys are doing their job, an indication of ability to clear toxic waste from the blood.
average rate of GHP
50mm Hg
NFP
NFP= GHP- (GCOP-CHP)
what forces drives filtration?
glomerular hydrostatic pressure
GHP / HPgc
what do capsular hydrostatic pressure (CHP/HPcs) and colloid osmotic pressure (GCOP/ OPgc) have in common?
these forces both oppose filtration
an increase in blood pressure will cause an increase in _____
glomerular hydrostatic pressure (GHP)
GHP is largely determined by
systemic blood pressure
small changes in GHP are normal homeostatic mechanisms to maintain glomerular filtration but severe hypertension can cause:
damage to the glomerulus and negatively impact kidney health.
common components of glomerular filtrate:
- water
- ions = sodium, potassium, chloride
- nitrogenous waste: urea, uric acid, creatinine
- organic molecules: glucose, amino acids
how might the contents of filtrate be altered if the filtration membrane is damaged or destroyed?
- increased protein (purotenia)
- presence of blood cells (hematuria)
how does the concentration of substances in filtrate compare to the concentrate in blood plasma?
the concentration of substances in filtrate is similar to their concentration in blood plasma.
what substances are not normally found in filtrate?
blood and large particles
what is the primary driving force (pressure) that produces glomerular filtration?
hydrostatic pressure of blood (blood pressure)
if the osmotic pressure in the glomerular capillaries increases, does the net filtration increase or decrease?
net filtration decreases.
label
patient: failing liver.
cannot make normal levels of albumin for blood plasma.
what effect on amount of filtration produced?
filtration production would increase
albumin: most important contributor to the blood’s osmotic pressure. osmotic pressure drops- filtrate rate increases. (less opposition to filtration rate)
increase in GFR does what to blood pressure
lowers blood pressure
(increases urine output, decreases blood volume and blood pressure)
decrease in GFR does what to blood pressure
blood pressure increases
(urine output decreases, blood volume increases bc water is conserved, and blood pressure will increase)
intrinsic control mechanisms:
auto-regulation mechanisms
allow the kidney to maintain a nearly constant GFR despite fluctuations in systemic arterial blood pressure to ensure that the kidney is able to filter enough blood to clear toxins and waste from the blood.
extrinsic control mechanisms:
maintain blood volume and systemic blood pressure, and under extreme conditions (hemmorhage) can lead to kidney damage if homeostasis is not restored.
GFR regulation mechanisms primarily affect which of the following?
glomerular hydrostatic pressure (HPg)
what are the intrinsic control mechanisms of glomerular filtration?
(aka renal autoregulation)
myogenic mechanism and tubuloglomerular feedback
renal autoregulation:
kidneys adjust its own resistance to blood flow by regulating the diameter of the afferent arterioles.
myogenic mechanism:
special response from smooth muscle of afferetn arteriole.
when afferent arteriole is strectched due to high blood volume (and blood pressure) the muscle cells reflexively constrict
reduces blood flow into the glomerulus - decreasing GFR
tubuloglomerular feedback
mediated by the macula densa cells of the juxtaglomerular apparatus (JGA)
macula densa: walls of the DCT, monitor osmolarity (NaCl concentration)
if osmolarity is too high macula densa releases vasoconstritor chemical that cause intense contriction of afferent areteriole.
reduces blood flow to the glomeruls, decrease NFP and GFP.
slows doesn the flow of filtrate through the nephron and allows more time for filtrate processing and NaCl reabsorption.
macula densa cells of the JGA regulate GFR through which intrinsic mechanims?
tubuloglomerular feedback
the myogenic mechanisms of renal autoregulation primarily involve smooth muscles in which blood vessels?
afferent arterioles
if afferent arteriole is constricted, what will happen to the glomerular filtration rate (GFR)
GFR will decrease
what does a high concentration of NaCl in the renal tubule at the juxtaglomerular apparateus most likely indicate?
insufficient NaCl reabsorption due to high GFR
through tubuloglomerular feedback mechanism, how would increase in filtration NaCl concentration affect afferent arteriole diameter?
afferent arteriole diameter would decrease (constrict)
Which cells release renin?
granular cells of the afferent arteriole
(also called juxtaglomerular cells) in the wall of the afferent arteriole release renin in response to low blood pressure.
Which cells release renin?
granular cells of the afferent arteriole
(also called juxtaglomerular cells) in the wall of the afferent arteriole release renin in response to low blood pressure.
Granular cells of the juxtaglomerular apparatus (JGA) regulate GFR indirectly through which mechanism?
renin-angiotensin mechanism
what is the function of the macula densa cells of the juxtaglomerular complex (JGC)
monitoring the NaCl content of the filtrate
which cells of the juxtaglomerular complex secrete renin?
granular cells
granular cells:
mechanoreceptors that sense blood pressure in the afferent arterioles. they secrete renin when the blood pressure drops and are import part of RAA regulatory pathway (extrinsic control mechanism)
glomerular filtration results in approximately ______ ml of filtrate every minute
120-125 ml
glomerular filtration results in approximately ______ ml of filtrate every minute
120-125 ml
almost all of the valuable things filtered in proximal tubule are reabsorbed immediately by the
pertibular capillary
