Glomerate filtration rate
GFR= how much blood can be filtered from glomerulus into tubule
- Passive process due to fluid dynamics
- Glomerular capillaries are far more permeable than other capillaries.
3 forces that determines GFR.
1- Glomerular capillary blood pressure due to larger afferent compared to efferent
arteriole- favours filtration.
2- Plasma- colloid osmotic pressure (mixture of proteins)- opposes filtration.
3- Bowmans’s capsule hydrostatic pressure (physical pressure exerted by liquid)-
opposes filtration.
= Net filtration pressure- favours filtration.
Intrinsic and extrinsic control.
- blood pressure is determined by GFR.
Blood pressure in the kidney is subject to intrinsic and extrinsic control.
Intrinsic= from within the kidneys
Extrinsic= external to the kidneys
Intrinsic control (autoregulation)
1. Myogenic mechanism
- Baroreceptor in arteriole- contract or dilates.
2. Tubuloglomerula feedback
- Specialised cells called Juxtaglomerular apparatus
Specialised collection of cells in DCT and afferent arteriole.
Granular cells in the efferent arteriole
Macula densa cells in the DCT monitors NaCl:
- High BP= high blood flow
- Increased BP= increased in blood flow therefore more filtrate so more NaCl
- More NaCl= macula densa cells send out a paracrine message to arteriole cells by
releasing ATP and adenosine.
Arteriole cells constrict and release blood flow.
Another level of control by the tubuloglomular feedback is when macula densa cells secrete
nitric oxide (vasodilator). This stops the action of ATP + adenosine.
Intrinsic and extrinsic control mechanisms of GFR work together to
maintain renal blood flow and GFR within appropriate ranges to meet the
body's metabolic demands and maintain homeostasis
Extrinsic control
- Overrides intrinsic control.
- Dehydration
- Purposely want to regulate GFR.
GFR= how much blood can be filtered from glomerulus into tubule
- Passive process due to fluid dynamics
- Glomerular capillaries are far more permeable than other capillaries.
3 forces that determines GFR.
1- Glomerular capillary blood pressure due to larger afferent compared to efferent
arteriole- favours filtration.
2- Plasma- colloid osmotic pressure (mixture of proteins)- opposes filtration.
3- Bowmans’s capsule hydrostatic pressure (physical pressure exerted by liquid)-
opposes filtration.
= Net filtration pressure- favours filtration.
Intrinsic and extrinsic control.
- blood pressure is determined by GFR.
Blood pressure in the kidney is subject to intrinsic and extrinsic control.
Intrinsic= from within the kidneys
Extrinsic= external to the kidneys
Intrinsic control (autoregulation)
1. Myogenic mechanism
- Baroreceptor in arteriole- contract or dilates.
2. Tubuloglomerula feedback
- Specialised cells called Juxtaglomerular apparatus
Specialised collection of cells in DCT and afferent arteriole.
Granular cells in the efferent arteriole
Macula densa cells in the DCT monitors NaCl:
- High BP= high blood flow
- Increased BP= increased in blood flow therefore more filtrate so more NaCl
- More NaCl= macula densa cells send out a paracrine message to arteriole cells by
releasing ATP and adenosine.
Arteriole cells constrict and release blood flow.
Another level of control by the tubuloglomular feedback is when macula densa cells secrete
nitric oxide (vasodilator). This stops the action of ATP + adenosine.
Intrinsic and extrinsic control mechanisms of GFR work together to
maintain renal blood flow and GFR within appropriate ranges to meet the
body's metabolic demands and maintain homeostasis
Extrinsic control
- Overrides intrinsic control.
- Dehydration
- Purposely want to regulate GFR.
