Fig. 17.8: Glomerular Apparatus
Glomerular Filtration
Capillary endothelium
lamina fenestra
Glomerular basement membrane
Podocytes
Visceral layer of Bowmans Capsule
GlomerularFiltrate
filter cutoff ~ 69,000 MW
negatively charged molecules retarded by - charged filter
Small solutes: [filtrate] = [plasma]
Glomerular Filtration Rate (GFR) ml filtrate formed
/ min
Depends upon renal blood flow and renal BP
Glomerular Filtration:
See Figure 17.9 for forces across glomerular capillaries that
favor filtration
Up - Downs in your future
GFR is constant over range of BPs that kidney can autoregulate its blood
flow.
90 --> 200 mm Hg
Glomerular Filtration Pressures: Fig 17.9
Glomerular Membrane Permeability
Substance
MW
MR
F/P
Inulin
5,000
1.4
1.0
Myoglobin
14,000
2.0
0.75
Hemoglobin
68,000
3.3
0.03
Serum
Albumin
69,000
3.6
0.001
Factors Affecting GFR
Glomerular Ultrafiltration Coefficient (Kf)
Hydrostatic Pressure
Renal Blood Flow
BC pressure
Osmotic Pressures in BC & Plasma
Glomerular Filtration Rate: Fig 17.10
Regulation of Renal Blood Flow
Note feedback loop in Figure 17.11 (Hmmmm........)
Regulation of Renal Blood Flow
Sympathetic nerves - NE onto ?1 on afferent arteriole to decrease
RBF and GFR
ANP - increase GFR by dilation of afferent arteriole
ADH - decrease by constriction
NO - dilates & increases
Endothelin, adenosine & ATP - constricts and decreases - via
stretch of vessels
Angiotensin II constricts afferent and efferent* at HIGH doses
- decreases
Autoregulation of Renal Blood Flow: Fig 17.11 &Fig 17.12
Mechanisms of Renal Autoregulation
Myogenic regulates blood flow
Tubule-glomerular feedback regulates by tubular-dependent flow
Increase/decrease GFR
Increased/decreased NaCl delivery to macula densa of DCT
*macula densa signals juxtaglomerular cells to change blood flow