Renal Science Flashcards
What is Osmolarity and units
- Concentration of osmotically active particles in a solution
- Osmol/l
Osmolality
osmol/kg water
Principle ions in intracellular fluid
K and Mg
Principle ions in extracellular fluid
Na, Cl and HCo3
Concentration of extra and intracellular fluid
Both 300mosmol
What happens to RBCs:
- Hypertonic solution
- Hypotonic solution
- Hypertonic: RBCs shrink, less water, more concentrated
- Hypotonic: more water, cell lysis and burst
Value for: Inulin clearance
125mls/min not absorbed or secreted
Value for: Glucose clearance
Zero as it is not filtered or secreted
Value for: Urea Clearance
Value for: H+ clearance
> GFR as more leaves the nephron than enters
What is PAH used for?
To calculate the renal plasma flow at 650mls/min
Ideal GFR marker
Should be filtered freely and not secreted or reabsorbed
Ideal Renal Plasma Flow marker
Filtered and complete absorbed
How to calculate filtration fraction
GFR/Renal plasma flow–> 125/650–> 20%
Osmolality
osmol/kg water
Principle ions in intracellular fluid
K and Mg
Principle ions in extracellular fluid
Na, Cl and HCo3
Concentration of extra and intracellular fluid
Both 300mosmol
What happens to RBCs:
- Hypertonic solution
- Hypotonic solution
- Hypertonic: RBCs shrink, less water, more concentrated
- Hypotonic: more water, cell lysis and burst
- 80% of nephrons
- Outer part of context
- Do not fully descend into the medulla
- Forms network of peritubular capillary
- Reabsorption and secretion
- Short loop of Henle
Cortical nephrons
- 20% of Nephrons
- Inner part of cortex
- Descend deep into the medulla
- Form Vasa Recta
- Concentrate and dilute urine
- Long loop of Henle
Juxtamedullary nephrons
Value for: Inulin clearance
125mls/min not absorbed or secreted
Value for: Glucose clearance
Zero as it is not filtered or secreted
Value for: Urea Clearance
Value for: H+ clearance
> GFR as more leaves the nephron than enters
What is PAH used for?
To calculate the renal plasma flow at 650mls/min
Ideal GFR marker
Should be filtered freely and not secreted or reabsorbed
Where do hormones affect the permeability of the kidney?
Late collecting duct
Distal Tubule:
- What is reabsorbed: early and
- Transporters?
- Drugs used here
- Early: NaCl, NaK2C transport
- Late: Ca reabsorption
- Blocked by thiazide diuretics
Forces acting upon the glomerular capillary
- Glomerular capillary blood pressure
- Bowman’s capsule hydrostatic pressure
- Bowman’s capsule oncotic pressure
- Capillary oncotic pressure
Value of Glomerular capillary blood pressure?
55mmHg
Value of Bowman’s capsule hydrostatic pressure?
15mmHg
Value of Capillary oncotic pressure?
30mmHg
Value of Capillary oncotic pressure?
0mmHg
Cause of increased Bowman’s capsule hydrostatic pressure and result on GFR?
Kidney stone, decreased GFR
Cause of increased Capillary oncotic pressure and result on GFR?
Diarrhoea, decreased GFR
Cause of decreased Capillary oncotic pressure and result on GFR?
Beverly burned patient, increase in GFR
Decrease in surface area for filtration and effect on GFR?
Decreased GFR
Extrinsic regulation of renal blood flow and GRF
Sympathetic via baroreceptor
Intrinsic regulation of renal blood flow and GFR
- Myogenic mechanism by stretch of smooth muscle
- Tubuloglomerular feedback mechanism
Proximal Tubule:
- What is reabsorbed?
- Transporters?
- 100% of glucose and AA
- 67% of salt and water
- NaKATPase
- Cl via paracellular pathway
- Water by osmosis
Ascending Loop:
- What is reabsorbed?
- Transporters?
- Drugs used here
- Na and Cl
- Triple cotransporter
- Impermeable to water
- Transporter blocked by diuretics
Descending Loop:
-What is reabsorbed?
- Highly permeable to water
- Does NOT reabsorb NaCl
- Fluid leaving descending loop is highly concentrated
Where do hormones affect the permeability of the kidney?
Distal tubule and collecting duct
Distal Tubule:
- What is reabsorbed: early and
- Transporters?
- Drugs used here
- Early: NaCl, NaK2C transport
- Late: Ca
- Blocked by thiazide diuretics
How does ADH act on the collecting duct?
- ADH binds to Type 2 receptors expressed by the renal tubular cells (g coupled protein receptors)
- Increase in cAMP
- Increase in aquaporins
- Increased permeability and water is reabsorbed
High ADH, hyper or hypo tonic urine?
High ADH, High water permeability, hypertonic urine (concentrated)
Low ADH, hyper or hypo tonic urine?
Low ADH, Low water permeability, hypotonic urine (dilute)
Effect of Nicotine and Alcohol on ADH
Nicotine stimulates ADH
Alcohol inhibits ADH
What receptors stimulate ADH
Hypothalamic osmoreceptors
How is the secretion of Aldosterone initiated?
- In response to increased K or decreased Na
- Stimulates Na reabsorption and K secretion
- Aldosterone increases the number and rate of production of transporters in distal tubule and collecting ducts to increase Na
What is the mechanism of ANP?
- Produced by heart, stored in atrial muscle cells
- Released in response to stretch due to increased circulating plasma volume
- Leads to excretion of Na and diuresis
- Decreases plasma volume
What is pK?
Tells us the pH at which the reaction will reach equilibrium
What drives bicarbonate ion reabsorption into the tubule?
H+ ion
How is tubular acid excreted by the kidney?
- Vast majority of H+ section if used for HCO3 reabsorption to prevent generation of acidosis
- Excreted as “acid phosphate”
What are the 3 components of the Juxtaglomerular Apparatus?
- Macula Densa
- Juxtaglomerular cells
- Extraglomerular mesangial cells
Role of Macula densa
- Sensory cells
- Senses ion composition in distal convoluted tubule and detects salt in tubular fluid
Role of Juxtaglomerular cells
- Effector cells
- Modified smooth muscle cells in afferent arteriole
- Secrete Renin
Role of Podocytes
-Interdigitating cell processes forming filtration slits
Role of Mesangial cells
Support cells and removal of debris
Difference between brush border at Proximal and distal convoluted loops
Proximal: “hairy” brush border
Distal: not “hairy”
Where do Loop diuretics work?
- Block triple co-transporter
- At ascending limp
Where do Thiazide Diuretics work?
- Block NaCl transporter
- At distal convoluted tubule
Diuretics work at apical or basolateral membrane?
Apical
How are thiazide and loop diuretics transported into the glomerular filtrate?
- By anion transport
- NADC transport
Where does Aldosterone work?
- Distal tubule and collecting ducts
- Increases synthesis of Na/KATPase
Action of Spironolactone?
- Decreases number of Na/K channels at distal and collecting tubules
- Decrease Na absorption
- Blocks aldosterone receptors
Mg and Ca are excreted when using Loop or Thiazide diuretics?
- Mg and Ca excreted in Loop
- Mg but NOT Ca excreted in Diuretics
Action of Carbonic Anhydrase inhibitors
- Proximal tubule
- Increased excretion of HCO3 with Na, K, H2O
- Glaucoma
Action of Aquaretcis
- Water loss without accompanying Na
- Competitive antagonists of vasopressin receptors
- Used in SIDH to correct hypoatraemia
What are the major prostaglandins in the kidney?
PGE2- medulla
PGI- glomeruli
-Both act as vasodilators
Action of Urosuric agents?
Block reabsorption of rate in proximal tubule
Cortical nephrons
- 80% of nephrons
- Outer part of context
- Do not fully descend into the medulla
- Forms network of peritubular capillary
- Reabsorption and secretion
- Short loop of Henle
Juxtamedullary nephrons
- 20% of Nephrons
- Inner part of cortex
- Descend deep into the medulla
- Form Vasa Recta
- Concentrate and dilute urine
- Long loop of Henle
