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Purpose of PAS stain?
Stains glycogen and mucosubstances. Used to demonstrate basement membranes and matrix.
Purpose of trichrome stain?
Stains basement membrane and matrix blue, some immune deposits stain red.
Purpose of Jones methenamine silver?
Demonstrates basement membrane and mesangial matrix of the glomerulus.
Which segments of the nephron can elongate?
PT and TL. The TAL and DCT are constant.
What tubular segments does the outer stripe contain?
Proximal straight tubule, TAL and collecting duct.
What tubular segments does the inner stripe contain?
DTL, TAL and collecting ducts.
What tubular segments does the inner medulla contain?
DTL, ATL and large collecting ducts (ducts of Bellini)
Which renal cells synthesize erythropoetin?
Cortical interstitial cells.
Where does angiotensin II act on the glomerulus?
It is a preferential efferent arteriolar constrictor.
What is the equation for renal clearance?
- U=urine concentration
- V=urine flow
- P=plasma concentration
What is inulin?
A water soluble substance that is freely filtered but neither reabsorbed nor secreted. The gold standard for measuring GFR.
Location of Urea Transporters.
UTA1: inner medulla collecting ducts (transports urea into the intracellular space)
UTA2: DTL (transports urea into tubule)
UTA3: IMCD (transports urea into inner medullary interstitium)
UTB: descending vasa recta (expressed widely elsewhere)
Which collagen chain can generate an immune reaction in Goodpasture Syndrome?
Collagen IV alpha3 chain.
- Tritiated water = TBW
- Mannitol, inulin = ECF
- Evans blue = plasma volume
Interstitial water is measured indirectly (ECF - Plasma volume)
- ICF measured indirectly
- (TBW - ECF volume)
Mechanisms for autoregulation of RBF.
- Myogenic: renal afferent arterioles contract in response to stretch.
- (increase in P produces increase in R to maintain constant RBF)
Tubuloglomerular feedback: increased renal pressure --> increased delivery of fluid to macula densa which causes constriction of afferent arteriole
What does clearance of PAH measure?
Effective RPF, it underestimates the true RPF by 10%
How do you measure GFR?
Clearance of inulin. It is filtered but not reabsorbed or secreted.
What is an indicator of prerenal azotemia?
Increased BUN/creatinine ratio of >20:1
How does an increase in the plasma [protein] effect the GFR?
It decreases the GFR because of an increase in the osmotic pressure of the glomerular capillary.
Relationship between filtered load, excretion rate, reabsorption and secretion.
If filtered load > excretion rate, then net reabsorption has occurred.
If filtered load < excretion rate, then net secretion has occurred.
Explain glomerulotubular balance.
Occurs in the proximal tubule, the purpose is to maintain a constant fractional reabsorption. If GFR increases, peritubular capillary [protein] and osmotic pressure increase causing more fluid reabsorption.
What special transporter does the TAL contain?
Na/K/2Cl co transporter, aka NKCC2.
What are the loop diuretics, where and what do they act on?
Furosemide, ethacrynic acid, bumetanide.
They inhibit the NKCC2 of the TAL.
What special transporter does the DCT contain?
Na/Cl cotransporter, aka the NCCT.
Cell types of the CD.
Principle cells: reabsorb Na and H2O, secrete K, sensitive to aldosterone and ADH.
Intercalated cells: A (secrete acid) and B (secrete base)
Factors that increase distal K secretion.
- 1. High K diet
- 2. Hyperaldosteronism
- 3. Alkalosis (acidosis decreases secretion)
- 4. Thiazide diuretics
- 5. Loop diuretics
- 6. Luminal anions
Which portions of the nephron are impermeable to urea?
DT, CCD and OMCD. IMCD are sensitive to ADH and can reabsorb urea.
How does PTH affect phosphate reabsorption?
It activates adenylate cyclase, generating cAMP which inhibits Na/phosphate cotransport. Thus it causes phosphaturia.
Process for water intake/deprivation.
Change in plasma osmolarity sensed by osmoreceptors in the anterior hypothalamus, which tells the posterior pituitary whether or not to release ADH.
What stimulates the secretion of PTH?
A decrease in plasma [Ca]