Glomerular Filtration and Urine formation

1. Urine Formation
Glomerular Filtration
Dr. Amir Bahadur

2. Body Fluids Composition

3. Urine Formation
a)Filtration (Glomerular)
b)Re-absorption
c)Secretion

4. DIAGRAMS/ FIGURES

5. Renal Corpuscle
Glomerulus+ Bowman’s Capsule

6. CUT through NEPHRON

8. a). Glomerular Filtration
Concepts of following are necessary
Renal Blood Flow (RBF)
Renal Clearance
Glomerular Filtration Rate (GFR)

9. Renal Clearance
• Volume of plasma cleared of any substance
in per unit time
• C= UV/P
 C is renal clearance
 U is urine concentration
 V is volume of urine
 Plasma concentration

10. RENAL BLOOD FLOW
• 25% of cardiac output
• Increased with increased pressure difference
between renal artery and vein and reduced
renal vascular resistance
• Decreased--- vice versa
• Vaso-dilators and vaso-constrictors effect
RBF
• Auto-regulated over wide range of pressures

11. RBF---Auto Regulation
i. Myogenic mechanism---- afferent
arteriole stretch, resistance increased,
RBF reduced and maintained.
ii. Tubulo-glomerular Feedback-----
increased RBF, increased fluid in DCT,
macula densa detects increased
pressure, vascular resistance
increased, RBF and maintained

12. RBF---- Auto regulation
iii. Neural Regulation: Sympathetic flow,
vasoconstriction of afferent arterioles,
regulate RBF
iv. Hormonal Regulation: JG cells, renin,
angiotensin II, vasoconstriction of
efferent arteriorles

13. Glomerular Filtration Rate (GFR)
• Filtrate through glomerulus in unit time
• Important predictor of nephron function
• Normal is 120mL/min
• Many factors causing changes in GFR but
kidneys optimize.
• Starling forces at bowman’s capsule & other
factors for filtration

14. Starling Forces

15. GFR---Starling Forces
• Glomerular hydrostatic pressure
• Glomerular oncotic pressure
• Bowman’s hydrostatic pressure
• Bowman’s oncotic pressure
Net filtration is in to the bowman’s capsule

16. GFR---other factors
• Pores/ fenestrations in capillaries
endothelium
• Negative charge on basement membrane of
bowman’s capsule
FILTRATE is plasma and solutes without cells.