Renal Flashcards
Renal Blood flow equation
- (MAP- Vascular Pressure) x Vascular resistance
- directly proportional to pressure gradient between the renal artery and renal vein
- inversely proportional to resistance of renal vasculature
- Q= (change of P)/ R -> Ohm’s Law
Renal Autoregulation
The kidney autoregulation.:It is anatomically arranged to allow fluid in the DISTAL TUBULE to alter afferent and efferent arteriole tone, and regulate GFR
-RBF will remain constant at 1200 ml/min as long as MAP remains between 50-180 mm/Hg
Neural autoregulation of the kidney
- Decreased GFR-> Increased Na+ and Cl- reabsorption in ascending limb of loop of Henle -> Decreased Na/Cl ions in distal tubule at macula densa
- Afferent arterioles DILATE in response & increase GFR
- Sympathetic response is to cause JG cells to release RENIN
- Angiotensin II: vasoconstriction & constriction of EFFERENT arteriole -> Increased glomerular pressure and increased GFR
What physiologic factors determine GFR?
- The pressure inside the glomerular capillaries
- The pressure in the Bowman capsule
- The colloid osmotic pressure of the plasma proteins
Proximal Tubule
Primary function: Active transport of Na+
- 60-70% of solutes reabsorbed here
- H2O & most ions are cotransported with Na+
- Osmotic force of Na+: Passive diffusion of H2O out of proximal tubule and into peritubular capillary
- Glucose, proteins, amino acids, acetoacetate ions, and vitamins almost COMPLETELY reaborbed
- Cl- ions passively transported to maintain electroneutrality
- H+ ions are SECRETED into proximal tubule in exchange for Na+ ions SECRETORY TRANSPORT
Complications of Transurethral Resection of the Prostate (TURP syndrome)
hypervolemia***** hyponatremia***** bladder perforation***** hemorrhage glycine toxicity ammonia toxicity electrical hazards hypothermia bacteremia.
Counter Current Exchange
-occurs in the Loop of Henle and Vasa Recta
-Concentration gradient causes fluid to be exchanged across parallel pathways
- essential for concentration and dilution of urine
- Thin descending limb
Permeable to H2O and small solutes (NaCL, urea)
Tubular fluid becomes progressively hyperosmotic
Thick ascending limb
Permeable to NaCl but impermeable to H2O
Tubular fluid becomes progressively hyposmotic
as it flows up the ascending limb
Descending limb= increased osmolarity (300-> 1200)
ascending limb= decreased osmolarity (1200-> 300)
Loop of Henle
- Primary function: Establish a hyperosmotic state within renal medulla for the purpose of water and salt conservation
- Water conservation produces concentrated urine
Thick Ascending Limb
-Impermeable to water: “the diluting segment”
- Na+-K+-2Cl- cotransporter
- Site of action for loop diuretics
-At physiologic pH, attach to the Cl- binding site of
the Na+-K+-2Cl- cotransporter, disabling it, and
inhibiting NaCl reabsorption
Distal Tubule
- Sodium, under the influence of aldosterone, is reabsorbed
- Potassium is secreted into the lumen in exchange for sodium (electroneutrality)
- Aldosterone influence is the MAIN regulator of K+ in the extracellular fluid
H+ is secreted by the late distal tubule against a concentration gradient
Acid –Base balance
Final step of urine acidification
Reabsorbs 10% of Water BUT ONLY PERMEABLE
under the influence of ADH
Aldosterone
- Acts directly on principal cells to increase Na+ reabsorption
- Secreted by the zona glomerulosa of the adrenal cortex
- It increases more luminal membrane sodium channels, = bring more sodium into the cell and increasing the activity of the ATPASE pump on the basel membrane
= Increases the number of luminal K+ channels which increases secretion of potassium - sodium absorption and potassium excretion
Collecting Duct
Permeability of the collecting duct to H2O is controlled by ADH
Water is absorbed OUT of collecting duct INTO the interstium
Urine is concentrated
ADH regulation
Osmotic Concentration of ECF:
- Osmoreceptors located near hypothalamus sense increased osmotic concentration and release ADH
- Stretching of atrial baroreceptors INHIBITS ADH
Renin
Protein enzyme released by kidney
Released by:
Beta adrenergic stimulation
Decreased perfusion to afferent arteriole
Decreased Na+ delivery to distal tubule
Acts on hepatic angiotensinogen-> Angiotensin I ->ACE in Lung ->Angiotensin II
Angiotensin II
Potent vasoconstrictor
Stimulates release of Aldosterone from Adrenal Cortex
ANF
Atrial Natriuretic Factor
– Peptide hormone synthesized, stored, and secreted by atria ( activated by atrial distention, stretch, and pressure)
- Increases urine flow
- Increases Na+ excretion
- Inhibits BOTH release AND end organ effects of:
Renin
Aldosterone
ADH
Can produce dose dependent decrease in BP
VERY POTENT DIURETIC
Volatiles and Renal disease
Temporary depression of Renal blood flow GFR Urine flow Electrolyte excretion
Diagnostic criteria for AKI
Diagnostic Criteria
- Absolute increase in serum Creatinine of 0.3 mg/dL OR
- Percentage increase in serum creatinine of 50 % AND
- Urine output less than 0.5ml/kg/hr