Glomerular Filtration

Question 1

Glomerular filtration

Answer 1

= filtration fluid into Bowman’s space from glomerular capillary tuft
- filtered fluid = filtrate. composed of H2O & electrolytes (no protein)

Question 2

GFR

Answer 2

= volume plasma filtered/unit time
decreases with age
around 80-120 ml/min
- changes if filtration is impaired

assessed with creatinine/inulin used bc they are completely filtered (100% excreted)

Question 3

FF

Answer 3

fraction of plasma being filtered
= GFR/RPF = 0.2
about 20% of plasma delivered to kidneys is filtered into nephron

Question 4

Glomerular filtration barrier

Answer 4

3 layers:

1. fenestrated endothelium
2. glomerular basement membrane
3. podocytes

• no interstitial tissue
• slit diaphragm- thin structure near basement membrane

Question 5

what is GFR influenced by?

Answer 5

• hydraulic pressure
• colloid osmotic pressure
• fluid pressure in capsule

Question 6

Resistance changes in renal arterioles effect on RBF/GFR

Answer 6

increased resistance in efferent arteriole: decrease RBF, increases GFR

vasoconstriction of afferent arteriole increases resistance, decreases RBF, bp, and GFR

vasoconstriction of efferent arteriole increases GFR, decreases RBF

dilation efferent arteriole decreases GFR, increases RBF

dilation afferent increases GFR and RBF

Question 7

regulation GFR

Answer 7

autoregulation (intrinsic)

• myogenic response to changes in bp. increase in pressure= stretch wall = stretch induced membrane depolarization = phosphorylation MLC = increase RA, back to normal flow
• Tubuloglomerular feedback (increase pressure = decrease RBF = increase GFR= increase tubular flow = increase preglomerular resistance = decrease RBF)

extrinsic regulation

• hormones (angiotensin, epinephrine)
• neural-sympathetic (NE, vasoconstriction of arterioles to decrease RBF and GFR)