Exam 4 Part 1 Flashcards
What are the 4 general functions of the kidneys?
- maintains body composition (volume, osmolarity, pH)
- excretes metabolites (urea, toxins)
- generates glucose (gluconeogensis)
- produces and secretes hormones/enzymes
What is the renal pelvis and ureter?
funnels urine into kidneys
What supplies blood to the kidney?
What removes blood (containing reabsorbed solutes) from the kidney?
supply: renal artery
removes: renal vein
What part of the kidneys contains the glomerulus?
cortex
What are medulla pyramids?
contains nephrons and vessels
What are minor and major calix?
where urine drips into renal pelvis
Where on the spine level are the kidneys located?
T12 - L3
The kidneys are _______________ which means they are outside the peritoneal cavity
retro-peritoneal
Kidneys receive ___% of cardiac output
25%
What is reabsorption?
solute moves from tubule lumen —> interstitial fluid
- tubule to peritubular capillary
What is secretion?
solute moves from interstitial fluid –> tubule lumen
- peritubular capillary to tubule
What is excretion?
removal of solute from tubule via urine excretion
What is filtration?
removing solute from bloodstream
- capillary to bowmans space
What is body mass balance?
total input = total output
What are the intakes and out takes for body mass balance?
intake: food/water and metabolic products
outtake: urine, renal vein, lymphatic output
What is the filtration rate fraction?
GFR/RPF
What’s the order tubules in the nephron?
- proximal tubule
- thin descending loop of Henle
- thin ascending loop of Henle
- thick ascending loop of Henle
- distal convoluted tubule
- collecting duct
How do you calculate water composition?
60% x weight
How do you calculate ECF?
20% x weight
How do you calculate ICF?
40% x weight
How do you calculate interstitial fluid?
75% x ECF
How do you calculate plasma volume?
25% x ECF
What’s the pressure that drives fluid from glomerulus capillary to Bowmans space?
hydrostatic pressure
What’s the pressure that drives fluid from Bowmans space to the glomerulus capillary?
osmotic pressure
Na+ and Cl- dominate extracellularly or intracellularly?
extracellularly
K+ and phosphate dominate extracellularly or intracellularly?
intracellularly
What’s more permeable, the cell membrane or the capillary membrane?
capillary membrane
What’s the driving force for solute movement?
osmolarity/osmolality
Intake of a isotonic NaCl solution…
type:
ECF volume:
ECF osmolarity:
type: isosmotic volume expansion
ECF volume: increase
ECF osmolarity: no change
Mild diarrhea…
type:
ECF volume:
ECF osmolarity:
type: isosmotic volume contraction
ECF volume: decrease
ECF osmolarity: no change
High NaCl intake…
type:
ECF volume:
ECF osmolarity:
type: hyperosmotic volume expansion
ECF volume: increase
ECF osmolarity: increase
Excessive sweating…
type:
ECF volume:
ECF osmolarity:
type: hyperosmotic volume contraction
ECF volume: decrease
ECF osmolarity: increase
Excessive water intake…
type:
ECF volume:
ECF osmolarity:
type: hyposmotic volume expansion
ECF volume: increase
ECF osmolarity: decrease
Adrenal insufficiency…
type:
ECF volume:
ECF osmolarity:
type: hyposmotic volume contraction
ECF volume: decrease
ECF osmolarity: decrease
What is GFR?
how much blood is filtered by glomerulus
How do you calculate filtered load of a solute?
GFR x [solute in plasma]
How do you calculate excretion rate of solute?
urinary flow x [solute in urine]
During reabsorption, filtered load ___ excretion rate of solute
filtered load > excretion rate
During secretion, filtered load ___ excretion rate of solute
filtered load < excretion rate
What is clearance?
measurement of renal function to clear a solute (vol/time)
Why inulin a good marker for GFR?
freely filtered by the glomerulus, is not secreted or reabsorbed in the tubules
* trapped in tubule lumen
How do you calculate the clearance (GFR) of a solute?
urinary flow x [solute in urine] / [solute in plasma]
For inulin, filtered load ___ excretion rate
filtered load = excretion rate
[creatinine] in plasma is __________ proportional to GFR
inversely proportional
What are the 3 filtration barriers that determine the composition of the ultra-filtrate?
- capillary endothelium
- glomerulus basement membrane
- podocyte foot process
Out of all 3 of these, which is the most resistant to large molecules?
1. capillary endothelium
2. glomerulus basement membrane
3. podocyte foot process
- podocyte foot process
(closet layer to bowman’s space)
Does hydrostatic pressure or osmotic pressure favor filtration?
hydrostatic pressure
Is hydrostatic pressure or osmotic pressure the driving force for GFR?
hydrostatic pressure
What happens to renal plasma flow if you restrict the afferent arterioles?
decrease
What happens to the hydrostatic pressure if you restrict the afferent arterioles?
decrease
What happens to the GFR if you restrict the afferent arterioles?
decrease
What happens to renal plasma flow if you restrict the efferent arterioles?
decrease
What happens to hydrostatic pressure if you restrict the efferent arterioles?
increase
What happens to GFR if you restrict the efferent arterioles?
increase then decrease
When you restrict the efferent arterioles, why does hydrostatic pressure increase?
resistance downstream (from restricting efferent) causes build up of pressure upstream resulting in LOTS of filtration initially (increase GFR)
protein beings to build up in capillary causing osmotic pressure to eventually rise above hydrostatic pressure = decreased GFR
How does changes in arteriole pressure affect glomerulus capillary and why does that affect GFR and hydrostatic pressure? And why?
no affect on any of them (**PRESSURE not resistance)
pressure needs to remain constant as not to filter too much solute
What are the 2 mechanisms that auto regulate renal function?
- myogenic mechanism
- tubuloglomerular feedback
What is the myogenic mechanism of autoregulation?
increased stretch of smooth muscles (die to increased pressure) in arterioles stimulates Ca2+ channels, causing increased intracellular Ca2+ = more tension = more resistance to counteract stretch
What is the tubuloglomerular feedback mechanism of autoregulation?
a SINGLE nephron senses increases in lumenal Na+ at the macula densa cells = constriction of arterioles = decreased GFR/RBF
How does Angiotensin II affect contraction and aldosterone?
increase contraction – increase resistance
increase aldosterone – increase sodium reabsorption
How does aldosterone secretion affect…
Na+ reabsorption:
extracellular fluid:
potassium excretion:
increase Na+ reabsorption
increase extracellular fluid
increase potassium excretion
What are 2 stimulators of aldosterone?
AT II
hyperkalemia (aldosterone will increase potassium excreation)
What does spironolactone block and compete for receptor?
aldosterone
What do diuretics do?
increase urine production to reducing fluid build up in body
What do prostaglandins (PGE2) do to kidney function?
local vasodilator which allows kidneys to increase flow
What is transcellular movement?
through cell
What is paracellular movement?
between cells
What affect paracellular movement?
voltage (Vte)
What affects transcellular movement?
max transport rate
What 3 epithelial characteristics affect solute movement?
- structure of tubule cells
- asymmetrical distribution of channels/transporters
- kinetic properties of transporters
Does the proximal tubule have complex or simple cells and are they tight or leaky?
complex (very involved in absorption and secretion)
leaky (easier for diffusion)
Glucose is transported via an active transporter which means it can become saturated. What is that affect on filtration, excretion, and reabsorption?
only affect reabsorption (only one that uses transporters) become saturated
What is Tm in glucose reabsorption and what happens there?
glucose transporter is saturated
resulting in excess glucose in tubule lumen that will be excreted
Why is there no glucose excreted at the beginning of the glucose Tm graph?
all the glucose is being filtered and reabsorbed
What is the threshold on the glucose Tm graph?
plasma concentration at which solute first appears in urine
What segment of tubule reabsorbes the most water?
proximal tubule
What solutes are moved across proximal tubule cells for reabsorption?
Na+
Cl-
H2O
only early…
K+
HCO3-
glucose
Fluid reabsorption in the proximal tubule is ____osmotic
isosmotic
____% of Na+ is absorbed in proximal tubule
67%
In proximal tubule, Na+ is transported paracellularly, transcellularly, or both?
both
What is the Vte charge in the early proximal tubule and why?
negative (-4 mV)
Na+ paracellularly leaving lumen making it more negative
What drives the reabsorption of Na+, Cl-, and H2O in early proximal tubule?
negative Vte
What is the Vte charge in the late proximal tubule and why?
positive (+4 mV)
Cl- paracellularly leaving lumen making it more positive
Since fluid being reabsorbed in proximal tubule is isosmotic, every solute being absorbed has a _______ molecule reabsorbed with it
H2O
* water passively follows solutes
Is hydrostatic pressure or osmotic pressure the driver for reabsorption?
osmotic pressure
What is GT balance?
67% of Na+ is always reabsorbed along the proximal tubule, regardless of the change in filtered load
What are the 2 factors that affect GT balance?
- peritubular factors (change in starling forces)
- luminal factors (tubule flow)
If you increase the filtration fraction does the osmotic pressure increase or decrease and how does this aid in the GT balance?
increase
* build up of proteins = increase osmotic pressure = increase reabsorption so that there isn’t too much filtration of solute
If you increase the filtration does that increase or decrease the hydrostatic pressure and how does this aid in the GT balance?
decrease
* enhances reabsorption so that there isn’t too much filtration of solute
If you increase filtration fraction there is an increase in tubule flow, what is the affect of on the amount of time of the solute in the tubule and reabsorption?
solute stays in tubule longer and concentration decreases slower = increase reabsorption
How much glucose, amino acids, and carboxylates are reabsorbed in proximal tubule?
almost 100%
What mechanism is glucose, amino acids, and carboxylates are reabsorbed in proximal tubule?
secondary active transport
* paired with Na+ reabsorption
How much potassium and calcium is reabsorbed in proximal tubule?
2/3
What ion reabsorption closely follows fluid reabsorption?
K+
Does K+ travel mainly paracellularly or transcellularly?
paracellularly
Where is most Ca2+ reabsorbed?
thick ascending limb
Does Ca+ travel mainly paracellularly or transcellularly?
paracellularly
Does Mg+ travel mainly paracellularly or transcellularly?
paracellularly
How much Mg+ is reabsorbed in proximal tubule?
15%
What ion is excreted the most and why?
phosphate
aids in acid release
How much phosphate is reabsorbed in proximal tubule?
80%
Does phosphate travel mainly paracellularly or transcellularly?
transcellularly
- active transport
Reabsorption of phosphate is ____ limited causing it be excreted in urine.
Tm limited
(uses secondary active transporter)
How much HCO3- is reabsorbed in proximal tubule?
80%
H+ excretion into lumen is necessary for both reabsorption of ________ and excretion of __________ acids
HCO3-
non-volatile
What 2 transporters are used to secrete organic anions?
anion coupled exchanger (apical)
DC2-coupled exchanger (basolateral)
What is an example of a organic synthetic anion?
PAH
What does the titration curve for PAH look like in terms of secretion?
Tm limited
increases then levels off
(active transporter on basolateral side for secretion)
