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Physio Review > Renal > Flashcards

Renal Flashcards

1
Q

8 core functions of the kidneys

A
  1. excretion of waste and foreign substances
  2. water/electrolyte balance
  3. extracellular fluid volume
  4. plasma osmolality
  5. RBC production (EPO)
  6. vascular resistance
  7. acid base
  8. vitamin D production
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2
Q

2 parallel circuits of blood flow in kidneys

A

both start with glomerular capillaries

  1. peritubular capillaries - cortex, 90%
  2. vasa recta capillaries- medulla, 10% (most in outer medulla)
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3
Q

from renal capsule to bladder

A

capsule –> cortex –> medulla –> minor calyx –> major calyx –> ureter –> bladder

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4
Q

pathway through the nephron

A

blood enters via afferent arteriole- bownman’s capsule/renal corpuscle - proximal convoluted tubule- HENLE (straight proximal tubule- descending thin limb- ascending thin limb- ascending thick limb)- macula densa- distal convoluted tubule- cortical collecting duct- medullary collecting duct- papillary duct

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5
Q

3 layers of the filtration barrier for capillaries in the glomerulus

A
  1. endothelium of capillaries
  2. capillary basement membrane
  3. interdigitated podocytes
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6
Q

proximal tubule vs loop of henle vs distal tubule

A

PT: high volume, low gradient reabsorption; brush border; lots of mitochondria

LH: makes interstitial osmolarity, poorly developed cell surfaces

DT: low volume, high gradient reabsorption; lots of folds; lots of mitochondria

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7
Q

what is clearance?

A

the volume of plasma completely cleared of any substance in 1 min; mL/min

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8
Q

two equations for excretion

A
  1. excretion= filtered + secreted- reabsorbed

2. excretion= U(concentration)*V(flow)

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9
Q

conservation of mass for kidney

A

PaRPFa= PvRPFv + U*V

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10
Q

formula for clearance

A

UV= PC

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11
Q

what does inulin measure? creatinine? BUN? PAH?

A

1) inulin, creatinine, BUN all measure GFR (what you clear is exactly what was filtered)
- creatinine is overestimate b/c there is some secretion (BUN= creatinine x 10)
2) PAH measures renal plasma flow b/c it is all excreted; have some in venous blood so actually multiply by 1.1

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12
Q

calculate renal blood flow from renal plasma flow? what is more and how do they relate to GFR? what is GFR?

A

RBF= RFP/1-hct

RBF>RPF>GFR>V
RBF= 25% CO
GFR= measure of overall renal function

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13
Q

what is the filtration fraction?

A

FF= GFR/RPF or 125/660

Inulin clearance/PAH clearance (normal= 20%)

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14
Q

Glomerular capillaries are +/- charged, so it inhibits the passage of +/- charged substances such as __

A

negatively charged for both, albumin

polycationic molecules are filtered freely

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15
Q

what is the equation for GFR? how is it regulated?

A

GFR= Kf * (Hydrog - Hydrob - oncoticg + oncoticb)

- regulated by changes in afferent/efferent arteriolar resistance

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16
Q

what happens to GFR, Pgc, and RBF when you constrict the efferent arteriole?

A

GFR and PGC increase

but constriction ALWAYS decreases renal blood flow

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17
Q

ways intrinsic autoregulation occurs to regulate GFR and RBF

A

1) smooth muscle myogenic theory
2) tubuloglomerular feedback theory- more Na in macula densa causes afferent arteriole to constrict
3) intrinsic vasodilators and vasoconstrictors

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18
Q

what is the take away from Fick’s principle in the kidney?

A

if blood flow is restricted to the kidney, the kidney requires less oxygen

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19
Q

what are Tm and RPT? which is reached first and why?

A

Tm- transport maximum
RPT- renal plasma threshold (mg/ml)
- RPT reached first because of splay

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20
Q

how do you calculate the Tm for glucose? PAH?

A
  • glucose is actively reabsorbed: Tm= PaGFR-UV
  • PAH is actively secreted:
    Tm= UV-Pa*GFR
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21
Q

what percent of water/Na/Cl/K is reabsorbed in the proximal tubule?
what percent of glucose/aa’s is reabsorbed in the proximal tubule?

A

2/3rds or 67% of water/Na/Cl/K reabsorbed in PT

100% glucose/AAs reabsorbed in PT

22
Q

how is Na+ transported in the loop of henle? what is the percent reabsorbed? which segment is impermeable to sodium?

A
  • Na/K/2Cl symporter
  • 25%
  • thin descending loop
23
Q

how is Na+ transported in the distal tubule? what is the percent reabsorbed? collecting duct?

A
  • NaCl symporter early
  • Na+ channels late
    ~5 %
  • collecting duct is 3%, Na channels only
24
Q

where is no water reabsorbed?

A
  • thin ascending & thick ascending limbs of Henle

- distal tubule

25
Q

what is a positive water balance?

A

intake > loss ; make hypoosmotic urine

26
Q

what is the threshold for change in plasma osmolarity to secrete ADH? threshold for baroreceptors?

A
  • greater than 280 mosms
    OR
  • decreased in bp by 10%
  • bp makes you more sensitive to osmolarity *
27
Q 
challenges to homeostasis : 
drink sea water
blood transfusion
saline transfusion
water deprivation/sweating
bleeding
concentrated urine
A

1) drink sea water- hyper expansion
2) blood transfusion- iso expansion
3) saline transfusion- hypo expansion
4) water deprivation/sweating- hyper contraction
5) bleeding- iso contraction
6) concentrated urine- hypo contraction

28
Q

what is the equation for the anion gap? what is it for vomiting/diabetes?

A

[Na]- ([Cl]+[HCO3-])= ~15 meq/L

vomiting= 15
diabetes= 35
29
Q

what contributes to the hyperosmotic gradient from cortex to medulla?

A

urea- 50%- 600 osmol
Na- 25%- 300 osmol
Cl- 25%- 300 osmol

30
Q

3 mechanisms that generate hyperosmotic gradient from from cotex to medulla?

A
  1. countercurrent multiplier- permeability differences for Na and H20
  2. urea cycle- leaking out in collecting duct & only participating in right loop
  3. countercurrent exchanger- slow vasa recta flow (permeable to everything) allows time for Na to move in and H20 to move out
31
Q

5 requirements for hyperosmolarity

A

1) long loops of Henle
2) blood & urine flowing in opposite direction
3) active salt pumping (in basolateral membrane of cells near TAL/DT/CD)
4) differential permeabilities
5) destruction takes days to re-establish

32
Q

what are the 4 ways of regulating renal salt excretion via afferent sensors?

A

a- venous (increased atrial stretch, increased ANP, natriuresis)
b- arterial (increased barros, decreased symp, decreased ADH)
c- hepatic sensors (increased liver p, decreased symp)
d- CNS sensors (increased Na in CSF, decreased symp)

33
Q

what is the sympathetic pathway for water/Na reabsorption

A

increased sympathetics decreases GFR by constricting afferent arteriole, which increases renin (RAAS) and increases Na reabsorption

34
Q

what are the 3 things that stimulate renin secretion?

A

1) afferent arteriole- perfusion pressure sensed by baroreceptors
2) afferent arteriole- sympathetic nerves that innervate
3) macula densa- tubuloglomerular feedback senses decreased NaCl

35
Q

what does reabsorption depend on in 3 parts of kidney?

A

1- proximal- filtered load
2- TAL- Na delivery rate
3- DT/CD- Na load remaining

36
Q

what are 3 things that cause K+ release from the cell? what percent is reabsorbed vs excreted?

A

1) epinephrine acting on alpha receptors
2) cell lysis (burns, surgery)
3) hyperosmolarity

85-95% is reabsorbed (decreases with more in diet)
15-80% is excreted (increased with more in diet)

37
Q

what are 5 things that cause K+ uptake by the cell?

A

1) epinephrine activating B2 receptors, especially during exercise
2) increased extracellular K+ stimulating the Na/K ATPase
3) insulin (especially following a meal)
4) aldosterone
5) hyposmolarity

38
Q

glomerulotubular balance vs. tubuloglomerular feedback

A

GT balance- 67% of what’s put in is reabsorbed
vs
TG feedback- Na sensed by macula densa controls afferent arteriole and GFR

39
Q

what is a non-volatile acid? what is a volatile acid?

A

not derived from CO2 (H2CO3 is the ONLY volatile acid- can be excreted as gas by lungs)

40
Q

what is the compensation for metabolic acidosis?

A
  • dec pH
  • dec Co2
    COMP: decrease CO2 more
41
Q

what is the compensation for respiratory alkalosis?

A
  • inc pH
  • dec Co2
    COMP: decrease HCO3-
42
Q

principle cell vs intercalated cell

A

principle cell: secretes K+ in exchange for Na (K+ balance), has AQP2 (water balance); few mits

intercalated cell: acid-base balance; reabsorbs K+ in exchange for H+ (can be used for NH4+ excretion), facilitates HCO3- reabsorption; lots of mits; only cells w/o cilia

43
Q

NaCl transport vs water transport % reabsorption in different compartments

A

NaCL: 67-25-5-3
water: 67-15-0-10/15

44
Q

menomic for evaluating acid base status

A

ROME- respiratory opposite, metabolic equal

same direction of change for pH & PaCO2

45
Q

normal pH, PaCO2, HCO3, H+

A

pH: 7.35-7.45
PaCO2: 35-45
HCO3-: 22-28
H+: 35-45

46
Q

what propels urine to the bladder?

A

walls of the calyces, pelvis, and ureter contract rhythmically and propel the urine along by peristalsis; ATP from myocardium

47
Q

what makes up the JG apparatus?

A
  • macula densa of thick ascending limb
  • extraglomerular mesangial cells
  • renin/ATII producing cells of the afferent arteriole
48
Q

T/F Cl- reabsorption in the PT exceeds water, while Pi absorption is slower

A

false- opposite is true (and Na parallels water)

49
Q

division of water

A

2/3 ICF 1/3 ECF

of the ICF 3/4 interstitial, 1/4 plasma

50
Q

Infusing saline is a hypo/iso/hyperosmotic fluid expansion?

A

hypo-osmotic; plasma has a higher osmolarity than saline

51
Q

what is CH20

A

free water clearance- the amount of pure water the kidney adds to the urine

Physio Review (6 decks)

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