glomerular filtration rate for MLT

2. Glomerular Filtration
• As blood flows through the glomerulus
protein-free plasma filters through the
glomerular capillaries into Bowman’s capsule
• This process is known as glomerular
filtration which is the first step in urine
formation

4. Glomerular Filtration Rate (GFR)
• The rate at which plasma is filtered by the kidney
glomeruli.
• An important measurement in the evaluation of kidney
function
• GFR = 125 mL plasma/min or, 180 L/day
• Plasma volume (70-kg young adult man) = about 3L, the
kidneys filter the plasma some 60 times in a day.

5. Renal blood flow
Renal blood flow to the kidney represents 20% of
cardiac output.
The blood flows to each kidney through a renal
artery.
 High blood flow rate (1200 ml/min).
Efferent and afferent arterioles are major sites of
renal resistance.

6. Renal Blood Vessels
• Afferent arteriole:
– Delivers blood into the
glomeruli.
• Glomeruli:
– Capillary network that
produces filtrate that
enters the urinary tubules.
• Efferent arteriole:
– Delivers blood from
glomeruli to peritubular
capillaries.
• Peritubular capillaries:
– Deliver blood to vasa recta

7. 3 processes
involved in Urine
formation
1.Glomerular
filtration
2.Tubular
reabsorption
3.Tubular
secretion

9. Glomerular Filtration
• Ultrafiltration of plasma in the glomerulus
Governed by 2 major factors:
1. Filtration coefficient (Kf)
2. Pressure gradient/ Starling forces (hydrostatic
and osmotic pressure gradients)

10. Mechanism of Glomerular Filtration
Filtration coefficient
1. Capillary permeability
2. Size of the capillary bed

11. Pressure Gradient

13. Factors Increasing GFR
1. Increase renal blood flow
2. Increase glomerular pressure
3. Increase blood pressure
4. Efferent arteriolar constriction

15. Factors Decreasing GFR
1. Increase plasma colloid osmotic
pressure
2. Increase Bowman’s capsule pressure
3. Afferent arteriolar constriction
4. Sympathetic stimulation

16. Measurement of GFR
Measuring renal clearance of various
substances
• Inulin
• PAH
• Creatinin

17. Regulation of GFR
Intrinsic
mechanism
Extrinsic
mechanism
Myogenic
mechanism
Tubuloglomerular
feedback
Neural
mechanism
Hormonal
mechanism

18. Myogenic mechanism
Arterial pressure
Stretching of blood vessels (afferent arteriole smooth muscle)
Secondary contraction of
Afferent arterioles
Renal blood flow decrease to normal

19. Tubuloglomerular feedback mechanism

20. Juxtaglomerular Apparatus

21. Neural mechanism

22. Hormonal/Autacoids mechanism
• Hormones / • Effect On GFR
Autocoids:
• Norepinephrine
• Epinephrine
• Endothelin
• Angiotensin II
• Prostaglandins
• Dec
• Dec
• Dec
• Prevents Dec
• Inc

23. Physiological conditions that alter GFR
Exercise Sympathetic
stimulation
Afferent arteriolar
constriction
GFR
Pregnancy BV
Hormonal changes
Vascular resistance GFR
Posture Sympathetic
stimulation
Afferent arteriolar
constriction
GFR
Sleep Circulatory activity GFR
Weather ECF GFR
Gender GFR
Age Loss of nephrons GFR
Food intake Protein diet GFR

24. Thank You