A&P final Flashcards
What is the osmotic pressure on the afferent side of the glomerular capillary?
28mmHg
what is an important control point that the body manipulates to maintain a normal level of blood flow and filtration?
vascular resistance
If the kidney sees that blood flow is too low what happens?
afferent arteriole relaxes to increase blood flow
If renal blood flow is too high, how does the kidney respond?
the afferent arteriole constricts to prevent over profusion
If we keep a normal blood flow in the kidneys at the afferent arteriole, it should maintain a normal
GFR
because filtration is a result of blood flowing through the kidney
what type of graph would you see in autoregulation of blood flow in the kidneys
what is the significance of the slant in this graph?
It shows that kidney autoregulation isn’t perfect. If it was the line would be flat.
Instead, the kidneys retain fluid when pressure is low and decrease fluid when pressure is high which helps us manage blood pressure long term
How is the plasma oncotic pressure in the systemic capillary different than the plasma oncotic pressure in the kidney?
In the systemic capillary it doesn’t change from the arteriole end to the venule end, but in the kidney, because there is so much filtration in the middle of the glomerular capillaries, the oncotic pressure on the efferent end of the glomerular capillary is more concentrated(36mmHg) than the afferent side(28mmHg).
Why is the oncotic pressure higher on the efferent side of the glomerular capillary?
Because we are loosing so much fluid in the glomerular capillary it concentrates the fluid that is leaving through the efferent end
What is the osmotic pressure on the efferent side of the glomerular capillary?
36mmhg
what is the osmotic pressure in the middle of the glomerular capillaries?
32mmHg
What is the pressure in the Ptubule
Bowmans capsule
18mmHg
what is the protein osmotic pressure in the early part of the tubule?
0
Why don’t the proteins that are necessary for the cells that make up the tubule count towards the protein osmotic pressure in?
Because they are tethered and not floating around so they don’t have any protein osmotic pressure associated with them
How to solve for the NFP of renal tubule
60mmHg πglomerular capillary promotes filtration
-32mmHg πaverage glomerular capillary opposes filtration
-18mmHgPtubule opposes filtration
=
10mmHg NFP
The NFP of the renal tubule drives what?
125mL/min filtration rate in a 30 year old healthy adult
What is the Filtration coefficient sometimes associated with and what does it do?
NFP
helps us figure out what the filtration rate is.
How does NFP factor into the filtration rate?
You multiply the filtration coefficient (constant) by the NFP
If the renal filtration rate is 125mL/min and NFP is 10mmHg, what is Kf?
12.5 mL/min/mmHg
125mL/min/Kf X 10mmHg
Net filtration pressure times the filtration coefficient equal=
blood flow
what is the second arteriole that sits behind the glomerular capillaries?
efferent arteriole
efferent arteriole tone/contraction is used by the kidney to
fine tune the GFR
If you occlude outflow in the efferent arterioles that would
drive up pressure in the glomerular capillaries which would increase filtration
If GFR is low what does the kidney do to fix this?
constricts the efferent arteriole
if GFR is too high what does the kidney do to fix this?
relaxes the efferent arteriole
What is the BP at the end of the efferent arteriole?
18mmHg
The afferent arteriole drops blood pressure by _______mmHg from the renal artery to the glomerular capillaries
40mmHg of resistance in the afferent arteriole
100mmHg-60mmHg=40mmHg
The efferent arteriole drops blood pressure by ______mmHg from the glomerular capillary to the end of the efferent arteriole
42mmHg of resistance in the efferent arteriole
60mmHg-18mmHg=42mmHg
The efferent arteriole has the highest _______ in all the blood vessels in the kidney
vascular resistance
__________% of everything that is filtered is reabsorbed
99%
__________% of everything that is filtered gets excreted out
1-2%
What is the reabsorption route from the cells that line the tubule and the interstitial matrix?
Through or between cells (water and small stuff) that make up the walls of the tubule
After something is filtered, if we want to hold on to it, how does it get into the blood?
through or between the cells that line the tubule-> matrix-> peritubular capillaries
cv system
What is the matrix intermediary place between tubules and vessels?
Name and what is is made of:
renal interstitium
proteins
ions/electrolytes
larger energy compounds
The net reabsorption pressure in the peritubular capillaries is high or low?
high
The net filtration pressure in the peritubular capillaries is high or low?
low
plasma oncotic pressure at peritubular capillaries is
πperitubular capillary
32mmHg
BP in the peritubular capillaries is
13mmHg
πRenal ISF is
15mmHg
physical fluid pressure of Peritubular ISF
PISF
6mmHg
NFP of renal ISF
-10mmHg
Net reabsorption pressure of the renal ISF
10mmHg
Vast majority of blood that moves through the kidney stays in the
cardio vascular system and passes through the efferent arteriole
What part of the blood is filtered in the kidney?
the plasma
What percent of the blood that moves through the kidney gets filtered?
a little over 10%
125mL/min /1100mL=11.36%
How much of the plasma gets filtered in the kidney?
1/5
Though which vessel does the blood plus everything that gets reabsorbed leave the kidney?
renal vein
How is the renal tubule shaped?
It wraps around and has a very convoluted shape
Which part of the nephron empties into our bladder?
renal tubule
ureter
bladder
The process by which we remove things from the body via the urine is termed what?
excretion
What is the excretion formula?
Filtration
-reabsorption
+secretion
Secretion is when the body:
physically pumps things into the renal tubule to get rid of them
The pathway that secretion takes is ______ of reabsorption
reverse
Pathway of absorption
through or between the cells in the renal tubule->
renal interstitium->
renal peritubular capillaries
Pathway of secretion
renal peritubular capillaries ->
renal interstitium->
through cells to tubule
occurs through specialized transport systems that are made to allow the body to get rid of specific compounds
Secretion is not just limited to toxic compounds and can also be ______
K+
If we’re reasonably healthy then we take in these ions in excess so the body secretes them?
K+ and Na+
What units are used for excretion?
mL (volume)
mol or mg (quantity)
How many capillary beds are there around the renal tubule?
2
1 is focused on filtration
1 is focused on reabsorption
When talking about the specialized transport processes that happen in the kidney we’re usually talking about which cells?
Tubule cells
what does the red line represent?
Normal conditions within the glomerular capillary for colloid osmotic pressure along the length of the capillary bed
if the kidney decided to filter more fluid at the glomerular capillary you would expect colloids to be _______
more concentrated
How do you increase the filtration rate in the glomerular capillary?
by squeezing the efferent arteriole
Which line would represent the kidneys filtering less fluid?
green line
By relaxing the efferent arteriole the fluid becomes less concentrated
Which line would represent the kidneys filtering more fluid?
blue line
By constricting the afferent arteriole the fluid becomes more concentrated
What is the filtration fraction?
A function of how much fluid is filtered
how much plasma has made it through the kidney
What is a normal filtration fraction?
20%
How do you solve for the filtration fraction?
GFR/Renal Plasma Flow
125mL/Min / 660mL plasma/min
= 0.19 no units
What is the most correct renal blood flow?
1,100mL/min
If the hct is 0.4, what is the plasma volume?
Renal blood flow is 1,100mL/min
40% is volume of RBC=440
so remaining 60% is the plasma volume=660
OR
0.60% plasma volume X 1,100mL/min
How to solve for Renal Plasma Flow?
0.60% plasma volume X 1,100mL/min
OR
Renal blood flow is 1,100mL/min
40% is volume of RBC=440
so remaining 60% is the plasma volume=660
Why don’t you have to worry about the protein oncotic pressure in the Bowman’s capsule?
We shouldn’t be filtering proteins so it is 0
If we increase resistance at the afferent arteriole what happens to renal blood flow?
it decreases
If we relax the afferent or efferent arteriole, this would have what effect on renal blood flow?
increase it
Healthy people have a pretty good renal autoregulation between a pressure of______ and _______
50mmHg-150mmHg
People in ICU can’t autoregulate d/t
Autoregulation is dependent on the afferent arteriole being able to dilate.
When people are sick in the ICU their vessels can’t relax as well as they normally would (long term HTN or uncontrolled DM) so they don’t control autoregulation very well
if your sick what kind of blood pressure do you need?
> 50mmHG
Autoregulation prevents
under profusion and over profusion
The kidneys are really good at autoregulating at ________pressures
really high
At a lower blood pressure, glomerular filtration is not as well
autoregulated
If we didn’t have good autoregulation at high blood pressure then what would happen?
We would spill massive amounts of fluid
Normal urine output for a healthy person is
1mL/min
As BP goes up what does urine output do?
increase d/t renal blood flow and GFR both increasing
As BP goes down what does urine output do?
decreases d/t renal blood flow and GFR both decreasing
If bp is at 60mmHG and blood flow is regulated but GFR is starting to fail you would expect the urine output to
slow down to try and conserve volume to increase BP
The kidney is just a bunch of blood vessels that split at various points. What is the terminal split point?
Afferent arterioles
What is the name of the process of “stuff” going from the glomerular capillaries and into the renal tubule?
Glomerular filtration
If we aren’t filtering everything we need to get rid of, what kicks in to help?
Tubular secretory processes
What is reabsorption?
98-99% of stuff being reabsorbed at peritubular capillary
explain this pic:
Sometimes our body filters but body doesn’t reabsorb
Explain this pic:
What is an example of something that follow this mechanics?
Filtration with partial reabsorption
Na+
Explain this pic:
What is an example of something that follow this mechanics?
Filtration of compound with complete reabsorption
glucose in a non-diabetic patient
Explain this pic:
Filtration and secreted completely. Body has a transport system that moves all of it into the renal tubule to be secreted.
No compound is left in the renal vein
Why would you see glucose in the urine?
BG is so high the PCT can’t reabsorb anymore
OR
something is wrong with the transporters
We can’t lose any more than ______ of the stuff that is filtered by the glomerular capillaries so ____ stays in the efferent arteriolar blood vessels
1/5
4/5
What is PAH?
para amino hippuric
acid
A diagnostic compound that we use to get a handle on the renal blood flow when you don’t have means to measure this via a probe or other way.
The removal of PAH from the body is highly dependent on how much blood is going through the kidney.
If all of the blood that goes into the kidney has PAH and none of the blood that comes out of the kidney has PAH then the more PAH that is missing the _______ the renal blood flow is.
higher
What does a lower PAH removal from the blood in the kidney mean?
A lower renal blood flow
How much do we reabsorb in mL/min in the normal circumstances?
124mL/min
How to solve for urine output
Blood flow is 125mL/min - Reabsorb 124mL/min= urine excreted 1mL/min
What is the innermost layer of the glomerular capillary made of?
endothelial cells- more permeable to more stuff than a generic systemic capillary.
What are the specialized openings in the renal glomerular endothelial cells called?
Fenestrations
What is the big piece of connective tissue called that sits superior to the endothelium layer of the glomerular capillary?
basement membrane
What is the name of the specialized epithelial cells that provide support in the epithelium layer of the glomerular capillary?
podocytes
What are the layer of the cell wall of the glomerular capillary?
endothelium
basement membrane
epithelium
podocytes are similar in function to what?
astrocytes in that they provide structure
What are slit pores?
openings between podocytes
littered in the basement membrane is
negative charges that help to repel negatively charged things form being filtered.
what kind of charge is on most proteins?
net negative
what prevents proteins from slipping through fenestrations?
net negative charges littering the basement membrane
What helps to prevent swelling in the glomerular capillary if the pressure is really high and helps keep the surface area of glomerular capillary in check?
podocytes
What happens if you have a super high bp for a long time, say a renal artery pressure of 200mmHg instead of 100mmHg?
The glomerular capillary pressure is now really high. Renal podocytes try to help with this but over time they swell and don’t work and then fall apart.
What is dextran?
A synthetic sugar that chemist modify to make smaller and larger depending on how many chains they link together
If we compare a neutral dextran of any radius’s filterability to something that is similar in size but positively charged, then the positively charged dextran is probably going to be:
more filterable because it doesn’t have the negative charges to be repelled by the fenestrations
A polyanion dextran has a ______ filterability
why?
Low
The charge on the sugar compound is now negative so it is repelled and prevented from filtering through the fenestration
The size of the sugars Dr. Smidt calls Dextrans are ________
very large
(like a hetastarch)
explain this chart
Less filterable:
larger
more negative
More filterable:
smaller
more positive
illustrates the importance of charge and size and it’s relationship to filterability.
What is the filterability of water?
1.0
What is the filterability of sodium?
1.0
What is the filterability of inulin?
1.0
how to use inulin
It’s injected into the patient and then provider looks at blood work and urine studies to see how much was filtered/cleared out.
What is the downsides to using creatinine compared to inulin to determine GFR?
Creatinine is easy to use but has a lot of variability and doesn’t follow the same kinetics through the kidney that inulin which makes it less accurate.
what is inulin?
A synthetic compound used to figure out what the GFR is. More accurate/sensitive than creatinine.
What is the filterability of myoglobin?
0.75
What is the filterability of albumin?
0.005
Why does it makes sense that albumin filtration is so low?
size
not efficient- we’d have to reabsorb it because we need to keep albumin.
Where does most of our reabsorption occur in the kidney?
Peritubular capillaries
Why don’t RBC get filtered in the kidneys?
They’re too big
If glomerular capillary blood pressure is low, how does this effect GFR?
GFR will be decreased
If glomerular capillary blood pressure is high, how does this effect GFR?
GFR will be increased
Because we autoregulate our renal blood flow pretty well, the _______ is autoregulated pretty well also
GFR
If we keep a pretty constant renal blood flow we should have a fairly constant ______
GFR, all things considered.
What does PAH stand for?
para amino hippuric
acid
The epithelium layer in the glomerular capillary is specialized to
provide support to protect from the high pressure they’re exposed to here.
What do podocytes look like?
little foot processes that have opening between them called slit pores
What part of the kidney gets blown out by having long term HTN?
glomerular capillary cell walls
If we wanted to maintain relatively constant blood flow in the kidney what would we have to have?
autoregulation through the afferent arterioles constricting and relaxing
