Physiology 3 Flashcards
Glomerular capillary endothelium is barrier to what?
RBC
Basement membrane (basal lamina) is barrier to what?
Plasma protein barrier
Slit processes of podocytes (glomerular epithelium) is barrier to what?
Plasma protein barrier
Glomerular capillary blood pressure
55mmHg
Cpaillary oncotic pressure?
30mmHg
Bowman’s Capsule Hydrostatic (fluid) pressure?
15mmHg
Bowman’s capsule oncotic pressure?
0mmHg
Net filtration pressure?
10mmHg
GFR?
rate at which protein-free plasma is filtered from the gomeruli into the Bowman’s capsule per unit time
Rate at which protein-free plasma is filtered from the glomeruli into the Bowman’s capsule per unit time?
GFR
Normal GFR?
125ml/min
Major determinant of GFR?
Glomerular capillary fluid (blood) pressure i the major determinant of GFR
GFR = ? x ?
Kf x net filtration pressure
Kf = filtration coefficient = how “holey” the glomerular membrane is
Extrinsic regulation of GFR?
Sympathetic control via barocreceptor reflex
Autoregulation of GFR? (intrinsic)
- Myogenic mechanism
- Tubuloglomerular feedback mechanism
What happens if the afferent arteriole constricts?
Blood pressure of the glomerular capillary will fall and the GFR will decrease
What prevents short term changes in systemic arterial pressure affecting GFR?
Autoregulation prevents short term changes in systemic arterial pressure affecting GFR
- myogenic
- tubuloglomerular feedback
Myogenic
If vascular smooth muscle is stretched (i.e. arterial pressure is increased), it contracts thus constricting the arteriole
Tubuloglomerular feedback mechanism
Mechanism remains unclear (involves juxtaglomerular apparatus)
If GFR rises, more NaCl flows through the tubule leading to constriction of afferent arterioles
Which structure senses NaCl content of tubular fluid?
Macula densa
What might cause the Bowman capsule fluid pressure to rise? and what would the effect be on the GFR?
Kidney stone would cause the Bowman’s capsule fluid pressure to increase and this would cause GFR to decrease
What could increase capillary oncotic pressure and what would the effect be on the GFR?
Diarrhoea would cause an increase in the capillary oncotic pressure and this would cause a decrease in GFR
What could cause capillary oncotic pressure to fall and what effect would this have on GFR?
Severely burned patients will have a lower capilary oncotic pressure and this will cause an increase in glomerular filtration pressure
Decrease in Kf (change in surface area available for filtration) and effect on GFR?
GFR would decrease (remember this is how “holey” the glomerular membrane is)
