DIT review - Renal 1 Flashcards
Describe kidney embryology (pronephros, mesonephros, metanephros)
- Pronephros
- Degenerates
- Mesonephros
- Forms temporary kidney during 1st trimester
- Later contributes to male genital system
- Caudal end becomes the ureteric bud which gives risk to ureter, pelvises, calyces, collecting ducts
- Metanephros
- Interaction with the ureteric bud induces differentiation and formation of glomerulus through to distal convoluted tubule
What vessel does a horseshoe kidney get stuck under?
Inferior mesenteric artery
What are the layers of the glomerular filtration barrier and what layers are responsible for size/charge?
- Fenestrated capillary endothelium
- Size barrier
- Basement membrane
- Negatively charged (contains heparin sulfate) and size barrier
- Podocyte foot process
- Visceral layer of Bowman’s capsule
- Negative charge layer
Describe components and funtion of the juxtaglomerular apparatus
- Decreased MAP -> decreased renal perfusion pressure sensed by macula densa cells of the distal tubule -> activation of juxtaglomerular cells of the afferent arteriole -> conversion of prorenin to renin which is released into the plasma -> renin catalyzes conversion of angiotensinogen to angiotensin I -> in lungs and kidney ACE converts angiotensin I to angiotensin II
What are the 3 stimulators of renin release
- 3 stimulators of renin release
- Beta-adrenergic stimulation
- Low Na+ in the DCT
- Low pressure in the afferent arteriole
Describe the course of the ureters in reference to vas deferens and uterine artery
“Water under the bridge”
Ureters pass under the uterine artery or under vas deferens
Retroperitoneal
Describe the fluid composition of the body
- 60-40-20 rule
- 60% of body mass is water, of that 60%:
- 40% is ICF
- 20% is ECF
What is the equation for renal clearance
- C = (U x V) / P
- C = Clearance
- U = Urine concentration
- V = Urine flow rate
- P = Plasma concentration
What substances are used to estimate GF
Inulin and Creatinine
- Creatinine is freely filtered but not secreted as much as PAH
- Inulin is freely filtered but not secreted or reabsorbed
What substance is used to estimate renal plasma flow?
- RPF = Blood going to the glomeruli + blood going to the tubules
- Can be estimated with PAH (PAH is freely filtered and secreted - clearance of PAH > GFR)
What is the formula for filtration fraction and it’s normal value?
- FF = GFR/RPF
- Normal FF = 20%
Describe the equations for
- Filtered load
- Excretion rate
- Reabsorbed
- Secretion
- Filtered load
- Filtered load = GFR x Plasma concentration
- Excretion rate:
- Excretion rate = urine concentration x urine flow rate
- Reabsorbed:
- Reabsorbed = filtered – excreted
- Secretion:
- Secretion = excreted - filtered
When does glucose appear in the urine?
- Glucose is filtered freely and completely reabsorbed in the proximal convoluted tubule by a sodium-dependent glucose transporter up until a saturation point at 375 mg/dL
- At 160-200 mg/dL some of the nephrons reach max and glucose begins to start appearing in the urine
- At 350-375 mg/dL, the transporters become fuly saturated and a lot of glucose enters the urine
Describe the rates of absorption in the proximal tubule of:
Na+, Cl-, K+, HCO3-, Urea, Glucose, Inulin, amino acids, creatinine, and PAH
Be able to graph these on a Tubular fluid / plasma filtrate graph
- Anything that falls below the horizontal line (1.0) – more of that soluble is being absorbed relative to water
- Anything that falls below the horizontal line – less of that solute is being absorbed relative to water
- The reason that Creatinine and Inulin levels within the tubule are rising is because they are not reabsorbed, but water is, so their relative levels go up
- PAH is not being reabsorbed and is also being secreted into the tubules
- Interpretation of graph:
- PAH is freely filtered and secreted
- Creatinine is also freely filtered but not secreted as much as PAH
- Inulin is freely filtered but not secreted or reabsorbed
- Clearance of Inulin = GFR
- Urea is freely filtered and poorly reabsorbed
- Na+ and K+ are reabsorbed at the same rate of water so their concentrations remain constant
- HCO3- is actively reabsorbed due to carbonic anhydrase
- Glucose and amino acids are almost 100% reabsorbed in the proximal tubule
What part of the nephron are divalent cations (Mg2+ and Ca2+) reabsorbed and how?
Thick ascending limb of loop of Henle
- Indirectly induces reabsorption of Mg2+ and Ca2+
- K+ enters the cell from the lumen via NKCC but then leaks back into the lumen, giving the lumen a slight positive charge
- Cations flow from lumen into cell down the electric gradient
