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Urine concentration

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... Henle is to remove NaCl from the lumen and deposit this NaCl in the interstitium ... Depends on net transport of NaCl across TAL (part of 'single effect' ... – PowerPoint PPT presentation

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Title: Urine concentration


1
Lecture 7
  • Urine concentration

2
Urine Concentration
  • The main function of the loop of Henle is to
    remove NaCl from the lumen and deposit this NaCl
    in the interstitium of the medulla.
  • Interstitial osmolality rises from the cortex to
    the tip of the medulla (corticomedullary
    osmolality gradient).
  • The maximal interstitial medullary osmolality
    occurs during antidiuresis (1200mOsmol).

p. 833 Ch. 37
3
PLASMA OSMOL 290-300 mOsm.
HIGH ADH
LOW ADH
Fig. 37-1 p. 831
4
WATER RESTRICTION
Increased water permeability
HIGH
1200 mOsm
HIGH WATER INTAKE
ADH Control
LOW
No water permeability
Fig. 37-2 p. 832
60 mOsm
5
WATER RESTRICTION
TAL/DCT Impermeable to Water. ONLY Pumps NaCl out
fig 14-15
CONCENTRATED URINE/LOW VOLUME
6
Hyperosmolality of Medulla
  • Depends on net transport of NaCl across TAL (part
    of single effect)
  • Limit of tubule-interstitium gradient at any one
    point is 200 mOsm.
  • Countercurrent multiplier system
  • multiplies the single effect of the 200 mOsm
    gradient
  • After 39 cycles, the interstitial fluid
    osmolality would be 1200 mOsm.

7
Countercurrent multiplier system
-TAL pumps NaCL -equilibrium forms -fluid shifts
thru tubule -TAL pumps more NaCL
Ch. 14 in Vanders Physiology or Fig 37-3 BB
8
Urea Recycling on Interstitial Medullary
Osmolality
  • Urea cycle
  • Absorption of urea from IMCD (intermedullary CD)
  • Secretion of urea from interstitium into the tALH
  • Carriage of urea up into the cortex and back down
    through the nephron.

9
UREA RECYCLING
IMCD is made Permeable to UREA by ADH
ONLY!
10
Medullary osmotic gradient
11
WATER RESTRICTION
Increased water permeability
HIGH
1200 mOsm
ADH Control
HIGH WATER INTAKE
LOW
No water permeability
Fig. 37-2 p. 832
60 mOsm
12
  • Potassium Excretion

13
POTASSIUM IS HIGH IN INTRACELLULAR FLUID
14
Like Sodium and Water, Ingested Potassium is
Largely Excreted
15
POTASSIUM DISTRIBUTION
  • 98 of total body potassium is in the ICF.
  • 2 of potassium is in ECF.
  • Normal plasma range for K is (3.5-5.0mM)
  • Low ECF K is necessary to maintain steep K
    gradient across membranes (cellular
    excitability).
  • Changes in ECF K can cause severe disturbances
    in excitation and contraction.
  • Cardiac rhythmicity and muscle paralysis
  • Hypo and hyperkalemia
  • Diarrhea and vomiting are major causes for
    hypokalemia (dehydration)

16
Potassium Excretion
Reabsorption from proximal tubule
(70) Henles ascending limb (20) Collecting
duct (10) Intercalated cells Secretion
into Collecting duct (initial collecting
duct) principal cells of CD (variable) Potassium
excretion depends on K secretion from the
principal cells.
fig 14-26 Vanders Phys.
17
(No Transcript)
18
HORMONAL REGULATION OF POTASSIUM UPTAKE INTO CELL
Insulin Epinephrine Aldosterone
19
Acidosis and Potassium uptake
Na-K pump
Co-transporter
note, opposite for alkalosis
High plasma H (low ph acidosis) Decreases K
uptake into cell by inhibiting pumps and
co-transporters, therefore you get reduced ICF K
20
Regulation of potassium excretion
Same principal as sodium, the more you consume,
the more you excrete to keep in potassium
balance.
fig 14-27 Vanders phys.
21
Actions of Aldosterone
4.
5.
1.
2.
3.
fig 14-13
Aldosterone actions ? Na channel activity
(luminal side reabsorption), ? Na/K ATPase
pump, ? K channel activity and
secretion/excretion
22
Regulation of K excretion aldosterone
23
K excretion loop thiazide diuretic stimulation
24
K excretion K sparing diuretics inhibition
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