Male Infertility Panel Discussion by Dr Sujoy Dasgupta
Renal Physiology (II) - Glomerular Structure & Filtration - Dr. Gawad
1. 1
RENAL PHYSIOLOGY
(II)
m
GLOMERULAR
STRUCTURE & FILTRATION
Mohammed Abdel Gawad
2. OBJECTIVES
2
Be sure that you know what is NEPHRON
Be sure that you know RENAL CIRCULATION
Formation of URINE Steps (General Aspect)
Glomerular Filtration Barrier
Glomerular Filtrate & GFR (definitions)
Starling’s Forces & Membrane Permeability
Dynamics of Glomerular Filtration
Glomerular Filtrate & Kf (definitions)
Autoregulation of GFR
Factors affecting GFR
3. OBJECTIVES
3
Be sure that you know what is NEPHRON
Be sure that you know RENAL CIRCULATION
Formation of URINE Steps (General Aspect)
Glomerular Filtration Barrier
Glomerular Filtrate & GFR (definitions)
Starling’s Forces & Membrane Permeability
Dynamics of Glomerular Filtration
Glomerular Filtrate & Kf (definitions)
Autoregulation of GFR
Factors affecting GFR
6. OBJECTIVES
6
Be sure that you know what is NEPHRON
Be sure that you know RENAL CIRCULATION
Formation of URINE Steps (General Aspect)
Glomerular Filtration Barrier
Glomerular Filtrate & GFR (definitions)
Starling’s Forces & Membrane Permeability
Dynamics of Glomerular Filtration
Glomerular Filtrate & Kf (definitions)
Autoregulation of GFR
Factors affecting GFR
7. Formation of URINE in 3 steps
7
Tubular Tubular
Reabsorption Secretion
Glomerular Excretion
Filtration
10. OBJECTIVES
10
Be sure that you know what is NEPHRON
Be sure that you know RENAL CIRCULATION
Formation of URINE Steps (General Aspect)
Glomerular Filtration Barrier
Glomerular Filtrate & GFR (definitions)
Starling’s Forces & Membrane Permeability
Dynamics of Glomerular Filtration
Glomerular Filtrate & Kf (definitions)
Autoregulation of GFR
Factors affecting GFR
14. GLOMERULAR BASEMENT MEMBRANE
STRUCTURE
14
Formed of:
Collagen type IV
Triple helix: 3 α-peptide chains with globular non collagenous
domain (NC1)
Abnormalities:
Mutation in α-peptide chains → no proper helix → hereditary nephritis
Antibodies against NC1 in kidney → anti GBM disease
Antibodies against NC1 in kidney & lung → Goodpastuer Syndrome
15. OBJECTIVES
15
Be sure that you know what is NEPHRON
Be sure that you know RENAL CIRCULATION
Formation of URINE Steps (General Aspect)
Glomerular Filtration Barrier
Glomerular Filtrate & GFR (definitions)
Starling’s Forces & Membrane Permeability
Dynamics of Glomerular Filtration
Glomerular Filtrate & Kf (definitions)
Autoregulation of GFR
Factors affecting GFR
16. 16
Glomerular Filtrate & GFR
Glomerular filtrate:
fluid that filters through the glomeruli into
Bowman's capsule
= plasma – (plasma proteins, plasma
proteins binbed substances & substances
with a MW > 70.000).
Glomerular Filtration Rate (GFR):
- definition: The quantity of glomerular
filtrate formed in all nephrons of both
kidneys / min.
- normal value: 125ml/min. 180 Liters/day.
18. OBJECTIVES
18
Be sure that you know what is NEPHRON
Be sure that you know RENAL CIRCULATION
Formation of URINE Steps (General Aspect)
Glomerular Filtration Barrier
Glomerular Filtrate & GFR (definitions)
Starling’s Forces & Membrane Permeability
Dynamics of Glomerular Filtration
Glomerular Filtrate & Kf (definitions)
Autoregulation of GFR
Factors affecting GFR
19. Movement of water:
Starling’s Forces & Membrane Permeability
19
The amount of water in each body compartment is
dependent on:
1- osmotic pressure
2- hydrostatic pressure
+ Membrane characteristics
26. Membrane Factors
Membrane permeability (s) is clinically relevant in disorders which
disrupt membrane integrity (e.g., sepsis).
Permeability of a membrane ranges from zero, completely
permeable, to one, completely impermeable.
32. GFR & Filtration Coefficient (Kf)
32
Glomerular Filtration Rate:
- definition: The quantity of glomerular filtrate formed in all nephrons of
both kidneys / min.
For the 10 mmHg
- normal value: 125ml/min. 180 Liters/day.
Filtration coefficient (Kf):
It is the GFR for both kidneys per mmHg of filtration pressure.
Normally = 12.5 For 1 mmHg
GFR = 12.5 X 10 = 125 ml/min
33. OBJECTIVES
33
Be sure that you know what is NEPHRON
Be sure that you know RENAL CIRCULATION
Formation of URINE Steps (General Aspect)
Glomerular Filtration Barrier
Glomerular Filtrate & GFR (definitions)
Starling’s Forces & Membrane Permeability
Dynamics of Glomerular Filtration
Glomerular Filtrate & Kf (definitions)
Autoregulation of GFR
Factors affecting GFR
34. Autoregulation of GFR
34
Under normal conditions (MAP= 80-
180mmHg) renal autoregulation maintains
a nearly constant glomerular filtration rate
A- Myogenic mechanism:
Laplace law:
Vessel wall tension
α Distending pressure X radius of the vessel.
When arterial pressure rises →
afferent arteriole stretches → vascular
smooth muscles contract → arteriole
resistance offsets pressure increase →
RBF (& hence GFR) remain constant &
vise versa
37. Autoregulation of GFR
37
B- Tubuloglomerular feed back mechanism
Juxtaglomerular Apparatus or Complex:
is a specialized region of a nephron where the afferent arteriole and Distal Convoluted
Tubule (DCT) come in direct contact with each other. Juxtaglomeruar Apparatus (JGA)
consists of:
1) Juxtaglomerular cells (modified smooth muscle cells) of afferent
arteriole including renin containing (synthesizes and stores renin) and sympathetically
innervated granulated cells which function as mechanoreceptors to sense blood
pressure.
2) Macula densa cells (Na+ sensors) of Distal Convoluted Tubule (DCT) which
function as chemoreceptors to sense changes in the solute concentration and flow rate
of filtrate.
40. Autoregulation of GFR
40
B- Tubuloglomerular feed back mechanism
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41. OBJECTIVES
41
Be sure that you know what is NEPHRON
Be sure that you know RENAL CIRCULATION
Formation of URINE Steps (General Aspect)
Glomerular Filtration Barrier
Glomerular Filtrate & GFR (definitions)
Starling’s Forces & Membrane Permeability
Dynamics of Glomerular Filtration
Glomerular Filtrate & Kf (definitions)
Autoregulation of GFR
Factors affecting GFR
42. Factors Affecting GFR
1. Renal Blood Flow :
42
- increase blood flow
through the nephrons →
elevates the glomerular
pressure → increases
the glomerular filtration
rate.
44. Factors Affecting GFR
2. Diameter of glomerular blood vessels:
44
i- mild constriction → increases the
glomerular pressure → increases the
Eff. Art. filtration rate.
constriction
ii- severe or moderate constriction →
decreases the glomerular flow rate →
decreases the filtration rate, because the
plasma will remain for a longer period of
time in the glomerulus → extra large
amounts of plasma will filter out →
increases the plasma colloid osmotic
pressure → paradoxical decrease in
GFR occurs despite the increase in
glomeular pressure.
45. Factors Affecting GFR
3. Factors affecting Net Filtration Pressure:
45
I. Arterial blood pressure:
-a rise in the systemic blood pressure →
an auto-regulatory mechanism (automatic
afferent arteriolar constriction) →
prevents the rise in the glomerular
pressure
II. Colloid osmotic pressure:
-Hypoproteinaemia will increase the
filtration rate.
III. Post renal obstruction makes back
pressure and increases the Bowman’s
capsule hydrostatic pressure which leads to
decreasing GFR.
46. Factors Affecting GFR
4. Factors affecting filtration coefficient (Kf):
46
I. Permeability of Glomerular capillaries
(hydrolic conductivity):
- Increase permeability of glomerular capillaries →
increases the GFR.
- Normally the permeability of the glomerular
capillaries and Bowman's capsule is absent for
substances of molecular weight higher than 70,000.
- MW:
Albumin: 70,000
Globulin: 165,000
Fibrinogen: 200,000
Hb:68,000
II- Surface area of the membrane:
if decrease, it will decrease GFR
e.g.
Chronic pyelonephritis
Chronic GN
47. The Concept Of Plasma
47
Clearance
Inulin clearance
Creatinine clearance
PAH clearance
48. 48
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