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Mictrurition Reflex
Filling vs. Voiding
- Filling:
- Stretch receptors - monitor volume
- Afferent fibers - send info to PMC
- SNS - stimulate internal sphincter
- PSNS - inactive
- Voiding:
- PSNS - stimulate detrusor muscle
- SNS - inactive
- Pudendal - reduce activity to external sphincter
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Mictrurition Nerves
- Detrusor muscle (PSNS - S2,3)
- External sphincter (pudendal n. - S2,3)
- Internal sphincter (SNS L2)
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Origins of the bladder
- majority - endoderm (urogenital sinus)
- trigone - mesoderm (mesonephros)
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3 kidney system and derivatives?
- pronephric - vestigial nephrotomes
- mesonephric - nephrogenic cords & mesonephric duct (ureteric bud in metanephros)
- metanephric - metanephric blastoma
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Origin of collecting system & excretory unit?
- Collecting system (CT --> ureter): ureteric bud - mesonephros
- Excretory unit (BC --> DCT): metanephros
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Wt1
transcription factor on mesenchyme responds to induction by uteric bud
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Bladder & Urethra development
- Wk 4-7: cloaca divided by urorectal system (ant-1o urogenital sinus & post-rectal canal)
- Wk 8: perineal body
- 3 mo: urethra outgrowths
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Wilm's Tumor
Wt1 mutation
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WAGR Syndrome
- Wilm's tumor
- Anidiria
- Genitourinary anomalies
- Retardation
- 11p deletion
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Potter's Sequence
- apical appearance - oligohydramnios
- anuria
- lack of kidney
- hypoplastic lungs
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Exstrophy of bladder & cloaca
ventral wall body defect associated w/epispadias
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Freely filtered substance?
Completely reabsorbed?
Completely secreted?
- Freely filtered substance: inulin or creatinine
- Completely reabsorbed: glucose
- Completely secreted: PAH
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Hereditary nephrotic syndrome
- heavy proteinuria & renal failure
- mutations in NPHS1 (nephrin) & NPHS2 (podocin)
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Nephrotic disease
- severe proteinuria
- severe edema
- NO change in GFR
- normal urine volume
- Affects PODOCYTES - impacts composition of filtrate
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Nephritic Disease
- mild proteinuria
- mild edema
- decreased GFR
- oliguria
- HEMATURIA
- Affects CAPILLARY endothelial integrity & diameter - impacts GFR
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Ultra filtration Pressure
Pgc - Pbs - Ogc = Net ultra filtration pressure
absorption: Ogc> Pgc
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Transporters in Proximal Tubule & Special Feature
- 1st half:
- Na/X symporter
- Na/H antiporter
- Na/K pump
- 2nd half:
- Na/H antiporter
- Na/K pump
- Base/Cl antiporter
- Ion reabsorption
Special Feature: secretion of H+, NH3, organic cations & anions
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Transporters in Thick Ascending limb & special feature of Loop of Henle
- Na/2Cl/K co transporter
- K leak channels
- Na/H exchanger
- Na/K pump
- Paracellular ion reabsorption
Special Feature: descending limb - hypotonic, ascending limb - hypertonic
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Transporters of DCT & special feature
- Na/Cl symporter
- ENaC
- Na/K pump
- Special Feature:
- K+ secretion (light/principal cells)
- H+ secretion & HCO3- reabsorption (dark//intercalated cells)
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Transporters of Collecting duct & Special Feature
- ENaCNa/K pump
- Special Feature:
- K+ secretion (light/principal cells)
- H+ secretion & HCO3- reabsorption (dark//intercalated cells)
- Aldosterone (inc. Na reabsorption & K secretion)
- ADH (inc. H2) permeability)
- ANP
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Ion Reabsorption:
Ca2+
Mg2+
PO4
- Ca2+: para (PT & TAL), trans (PT* & DT)
- Mg2+: para (PT & TAL*), trans (DCT)
- PO4: trans (PT - SLC34A)
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Urea reabsorption in PCT, loop of Henle & Collecting duct - transporters
- PCT: reabsorbed - passive diffusion & solvent drag
- Loop of Henle: secreted - UT2
- Collecting duct: reabsorbed - UT1 & UT4 (ADH regulated)
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Diuresis vs. Antidiuresis
- Diuresis: high volume, hypotonic (-ADH)
- Antidiuresis: low volume, hypertonic (+ADH)
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ADH effect determined by plasma osmotic pressure:
hypovolemic
hypervolemic
- hypovolemic: enhanced response
- hypervolemic: dampened response
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Controls of Na excretion
- fractional Na excretion
- RAAS
- SNS
- ADH
- ANF
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Renal Effects of Angiotensin II
- stronger effect on efferent arteriole
- inc. GFR dec. RPF
- inc. proximal Na reabsorption
- +
- dec. blood flow of vasa recta
- inc. loop Na reabsorption
- = dec. Na excretion & H2O excretion
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Effects of Aldosterone
normally
excessively
- Normal:
- increased Na reabsorption & K secretion
- Excess:
- Na retention (hypervolemia, hypertension, edema)
- K wasting (weak muscles, ECG changes, constipation)
- H wasting (alkalosis-tetany, cramps)
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