Card Set Information
BC Nurse Anesthesia
transport urine from kidneys to the bladder
Hollow and viscous
temporary urine storage
muscle contraction is required to empty the bladder
transports urine from the bladder out of the body
Why does the right kidney sit lower than the left
right kidney is crowded by the liver
on the medial (concave) side of the kidney
where all vessels, nerves, lymph, and ureters enter and exit the body
fibrous capsule that helps to prevent kidney infection
adipose tissue that cushions the kidney and helps to connect it to the abdominal wall
about the size of a fist
3 major areas of the kidney
-contains renal pyramids that are separated by columns
pelvis- flat funnel shaped tube lateral to the hilus
medullary pyramid and its surrounding capsule
Purpose of the renal pelvis
collects urine, urine flows down ureters and into the bladder
Renal blood flow
22% of CO or 1100 ml / min
Major path of renal blood flow
renal artery (to smaller branches) to afferent arterioles, glomerulus, efferent arterioles, peritubular capillaries
2 capillary beds of the kidneys
glomerular and peritubular
separated by efferent arterioles which regulate the hydrostatic pressure in both sets of capillaries
Venous drainage of the kidneys
peritubular capillaries drain into the venous system and end in the renal vein
T or F, the kidney can control the hydrostatic pressure in both capillary beds by altering the resistance. This changes GFR and tubular reabsorption to maintain homeostasis.
-what is it?
functional unit of the nephron
1 million / kidney
we lose 10% / decade after age 40
T or F, we have exactly the amount of nephrons that we need?
F, we have more than we need. So as we age and lose nephrons, others pick up the slack
tuft of glomerular capillaries
glomerulus and bowman's capsule only
or nephron minus the tubules
collects tubular fluid (eventually urine) that gets filtered from glomerular capillaries
Path of tubular fluid in the nephron
bowman's capsule to renal tubules (PCT to LoH to distal tubule) then to collecting ducts and finally to the renal pelvis
What's the difference between the cortical and juxtaglomerular nephrons?
Difference is how deep the LoH goes into the kidney
Cortical have short LoH (only go a little way into the medulla)
JG- longer LoH (go deep into the medulla)
What percent of nephrons are juxtaglomerular?
What is the significant of the juxtaglomerular nephrons?
important for generating an osmotic gradient in the medulla
this becomes responsible for water reabsorption
creates a dilute or concentrating urine depending on our needs
juxtaglomerular nephron blood supply
long efferent arterioles that go down into outer medulla and divide into special peritubular capillaries (vasarecta)
lie side by side with the LoH
3 layers of the glomerular capillary
Inner to outer:
epithelium (podocytes)- specific to glomerular capillary
What's the purpose of having 3 layers of the glomerular capillary?
Ability to filter more water and solutes than the normal 2 layer membrane
Does the glomerular layer allow proteins to pass? Why or why not?
No, 1) they are too large, 2) both the proteins and the membrane layers have negative charges which repel each other
type of junctions / pore of the epithelial layer
slit junctions or slit pores (may be labeled as tight junctions in some sources)
Where are mesangial cells found?
found in-between and within the loops of the glomerular capillaries
cell type, not a layer
Purpose of the mesangial cells
Phagocyte- remove trapped foreign material from the basement membrane
Myofilaments- can contract to reduce surface area available for filtration?
excretion of metabolic waste products
regulate water and lytes
regulate osmolarity (LoH and vasarecta)
regulate BP (renin)
secretion, metab, and excretion of erythropoietin to stimulate RBC production
activation of vitamin D
blood to urine
filtering of plasma like fluid thru glomerular capillaries thru Bowman's capsule to the renal tubules
What substances get filtered by the glomerulus?
Most substances in the plasma with the exception of proteins and cells
urine to blood
substances get reabsorbed from the tubular fluid back into the blood thru the peritubular capillaries
blood to urine
substances get actively secreted from the blood into the tubular fluid for excretion
T or F, excretion = filtration - reabsorption - secretion
Excretion = filtration - reabsorption
What 2 ions tend to be secreted by the tubules?
H and K
What is the goal of glomerular filtration?
Eliminate waste products while retaining water and important electrolytes to obtain ideal ECF composition
What waste products from metabolism get filtered and eliminated?
Urea- from AA
Creatinine- from muscle creatine
Uric acid- from nucleic acids
Bilirubin- from Hbg
Are electrolytes most excreted or reabsorbed?
Are AA and glucose excreted or reabsorbed?
Provided their levels are below the threshold, they won't spill into the urine
What is the composition of the glomerular filtrate?
Like plasma, but without plasma proteins and cells
180 L/ day
125 ml/ min
What determines GFR?
: hydrostatic pressure (pushing) and colloid osmotic pressure (pulling) in
What is the net filtration pressure of GFR? What factors determine this?
Net filtration pressure = 10 mmHg
Net filtration pressure =
glomerular hydrostatic pressure (60 mmHg)
- Bowman's capsule pressure (18 mmHg)
-glomerular colloid osmotic pressure (32 mmHg)
Why is the colloid osmotic pressure of Bowman's capsule not a factor in GFR?
There is no protein
What is the filtration coefficient as it relates to GFR?
permeability x surface area available for filtration
sounds like Fick's Law
What is the filtration fraction?
How is it calculated?
fraction of the plasma flowing thru the glomerulus that actually does get filtered
FF= GFR / renal plasma flow= 22%
How do we know that most of the plasma volume gets reabsorbed?
GFR = 180 L / day
but we don't urinate that much / day!!
T or F, the permeability of the glomerular capillaries is 10X greater than that of other capillaries?
F, 50X greater
What size substances are filtered by the glomerulus?
What size are not filtered?
Freely filtered- molecules with diameters < 4nm, (lytes and glucose)
Not filtered- >8nm (proteins)
What factors affect what gets filtered by the glomerulus?
Size of the molecule
Size of the capillary bed
How do the mesangial cells affect the size of the capillary bed?
They have myofilaments that can contract to decrease the surface area available for filtration
What substances would cause contraction of the mesangial cells to decrease the SA area for filtration?
What would cause relaxation and increase the SA?
: angio2, vasopressin, NE
How does the charge of the glomerular capillaries affect filtration? Is this more or less important than the size of the molecules?
Basement membrane has a negative charge and so does albumin, hence it is not filtered
Charge has a greater effect than size
What factors affect GFR?
Renal blood flow
Glomerular capillary hydrostatic pressure
Bowman's capsule hydrostatic pressure
Glomerular capillary osmotic pressure
Changes in filtration coefficient
Formula for calculation of renal blood flow
renal artery pressure - renal vein pressure
renal vascular resistance
What is renal artery pressure?
What is renal venous pressure?
Renal artery pressure = systemic arterial pressure
renal venous pressure= 3-4 mmHg
What controls renal vascular rx?
main rx vessels are the afferent and efferent arterioles- contraction of either reduces RBF
rx is increased by decreased renal blood flow
At what MAP does renal auto regulation occur?
in this range, RBF and GFR remain constant
Why is RBF 10X than is required for kidney metabolism?
To allow the kidneys to eliminate waste products
How does the SNS affect renal blood flow and GFR?
activation causes VC of afferent and efferent arterioles
How do NE, epi, and endothelin affect RBF and GFR?
Cause VC of afferent and efferent arterioles
Where is renin secreted from? What causes its secretion?
Decreased RBF (macula densa sense a decrease in Na and Cl)
How does renin affect RBF and GFR?
Activates RAAS, angio 2 is produced
Angio2 preferentially constricts the efferent arteriole
GFR is increased
How does ANP affect RBF and GFR?
Released from atria in response to plasma volume expansion
increases glomerular hydrostatic pressure
Reabsorption of Na and water are inhibited
RBF and GFR are increased
How do prostaglandins, bradykinin, and NO affect RBF and GFR?
They are all VD
RBF and GFR are increased
What is the purpose of renal auto regulation?
Maintain O2 and nutrient delivery
Removal of waste products
As RBF increases, what happens to GFR?
It increases and vice versa
How does the JGA help to maintain GFR?
Macula densa senses a decrease in Na and Cl (increased reabsorption of both due to decreased GFR)
1) decreases rx in the afferent arterioles to increase glomerular hydrostatic pressure
2) renin is released causing angio2 to be produced, causing an increase in efferent arteriolar rx
What is the tubuloglomerular feedback mechanism?
Provides feedback to both the afferent and efferent arterioles for auto regulation of the GFR when BP changes
How does the tubuloglomerular feedback mechanism work?
Activated by decreased BP, decreased GFR and decreased flow at LoH
Decreased Na Cl concentration is sensed by macula densa (more time for reabsorption because of decreased flow), so...
renin and angio2 are released
decreased rx of afferent arterioles
VC of efferent arterioles (angio 2)
increased glomerular hydrostatic pressure
What are 2 mechanisms for renal auto regulation?
tubuloglomerular feedback mechanism
How does the myogenic mechanism work to maintain renal blood flow?
smooth muscle of afferent arterioles contracts in response to stretching
due to contraction, rx is increased
decreased GFR (back to normal)
What happens to RBF with a MAP < 70 mmHg? What about with a MAP < 40-50 mmHg?
<70 decreased RBF
<40-50 glomerular filtration stops
How does increased glomerular capillary hydrostatic pressure effect GFR?
It increases it
What 3 factors affect glomerular capillary hydrostatic pressure?
afferent arteriolar tone
efferent arteriolar tone
If we increase systemic BP, how is glomerular capillary hydrostatic pressure affected?
It is also increased
What effect does decreased afferent arteriolar tone (vasodilation) have on GFR?
Increased blood flow
Increased glomerular capillary hydrostatic pressure
What effect does increased afferent arteriolar tone (vasoconstriction) have on GFR?
Less blood flow
Decreased glomerular capillary hydrostatic pressure
What effect does increased efferent arteriolar tone (vasoconstriction) have on GFR?
Rx to outflow
Increased glomerular capillary hydrostatic pressure
GRF is increased, to a point (as long as blood flow doesn't back up and decrease renal blood flow)
What would cause an increase in Bowman's capsule hydrostatic pressure?
pushes back into the glomerular capillaries
What affect would an increase in Bowman's capsule hydrostatic pressure have on GFR?
What would increase the glomerular capillary osmotic pressure?
An increase in plasma protein concentration
What effect would an increase in the glomerular capillary osmotic pressure have on GFR?
Plasma proteins pull fluid back into the glomerular capillaries
This opposes filtration
What does an increase in the filtration coefficient mean? How does this affect GFR?
Increased SA or permeability to filtration
GFR is increased
HTN and DM can cause thickening of the blood vessels, thus decreasing the effective SA available for filtration- how does this effect GFR?
GFR is decreased
How does acute HTN affect GFR?
What effect do chronic uncontrolled HTN, DM, kidney stones, renal artery stenosis, and SNS stimulation have on GFR?
GRF is decreased
How do ACEI effect GFR?
Decrease in efferent arteriolar rx
(angio 2's effect of preferential VC of the efferent arteriole is blocked)
This causes decreased glomerular capillary hydrostatic pressure
Describe the path of the glomerular filtrate
Filtered from the glomerular capillaries
proximal tubule (cortex)
LoH (dips into medulla)
What is urine composed of (reabsorption, secretion, filtrate)?
Urine = glomerular filtration - tubular reabsorption + tubular secretion
In what ways can tubular reabsorption occur?
active transport (Na/K/ATPase pump)
co-transport with Na+
What substances undergo co-transport with Na+?
What direction are they traveling in?
What is counter transport?
A substance going in the opposite direction as Na+
Na+ is reabsorbed in exchange for H+ being excreted
Primary active transport
coupled directly with the energy source
Secondary active transport
AKA co-transport with Na+
coupled indirectly to an energy source
Active only because the concentration gradient for Na+ set up by Na/K/ATPase pump
What is the major function of the PCT?
Na+ reabsorption (about 2/3's occurs here)
enhanced by angio 2 and NE
Glucose secondary active transport
Na+ concentration gradient set up by the Na/K/ATPase pump allows Na+ to travel down it's concentration gradient (tubular fluid to ISF)
glucose travels with the sodium and is reabsorbed
AA are reabsorbed this way as well
How is water reabsorbed?
Passively by osmosis
can only move if the membrane is permeable to it, regardless of the concentration gradient
Water often moves with Na+
As water moves by osmosis, it can carry solutes with it
Describe the permeability of the proximal tubule to water and ions
Describe the permeability of the ascending LoH to water
Describe the permeability of the distal tubules, collecting tubules, and collecting ducts to water
dependent on ADH and insertion of aquaporins
Where does the PCT receive filtrate from?
How much Na and water is reabsorbed?
Why is the PCT well suited for active transport ?
Lots of mitochondria and carrier proteins
Na, water, and glucose and AA get reabsorbed
What does the PCT secrete?
organic acids, H+ ions, bases, bile salts, catecholamines
LoH: thin descending's permeability to water
very water permeable
moderate permeability to solutes
simple diffusion (few mitochondria)
LoH: thin and thick ascending's permeability to water
key to generating concentrated urine
T or F, the thick ascending limb of the LoH will reabsorb 25% of filtered Na, Cl, K, and large amts of Ca, bicarb, and Mg
Loop diuretic site of action
thick ascending limb of the LoH
In what part of the tubules is the JGA located?
first part of the distal tubule
What does the diluting segment of the early distal tubule reabsorb?
Is it permeable to water?
What is the site of action of thiazide diuretics?
early distal tubule
Late distal tubule- what is reabsorbed? secreted?
water permeability controlled by ADH
What is the site of action of the K sparing diuretics?
late distal tubule
What is the final site for processing urine?
medullary collecting duct
In the medullary collecting duct how is permeability to water controlled?
Are the collecting ducts permeable to urea? Why do we care?
Yes, unique b/c urea in the tubular fluid can be reabsorbed
urea increases the osmolarity of the interstitial fluid in the medulla, important in making a concentrating urine
How are the collecting ducts involved in acid base regulation?
Secretes H+ against a concentration gradient
How does increased BP affect reabsorption?
How does an increase in plasma proteins effect colloid osmotic pressure? reabsorption?
How do aldosterone and angiotensin 2 affect Na and water reabsorption?
How does ADH affect Na and water reabsorption?
How does ANP affect Na reabsorption?
How does PTH affect phos and ca reabsorption?
decreased phos reabsorption
increased ca reabsorption