US Lecture 3 - Renal Blood Flow and Glomerular filtration Flashcards
What is glomerular filtration?
Formation of an ultrafiltrate of plasma in the glomerulus
What is an abrupt fall in glomerular filtration called?
Renal failure
What can lead to reduced glomerular filtration?
Abnormalities in renal circulation
What does the filtration system look like? FITB


What type of process is glomerular filtration?
Passive process with fluid ‘driven’ through semipermeable wall of glomerular capillaries into Bowman’s Capsule space by hydrostatic pressure of the heart
What is the fenestrated endothelium of capillaries and Bowman’s capsule permeable to?
Fluids, small solutes - freely filtered
What is the fenestrated endothelium of capillaries and Bowman’s capsule impermeable to?
Cells, proteins, drugs carried bound to protein
What is the ultrafiltrate and what does it look like?
A clear fluid, completely free from blood and proteins, containing electrolytes and small solutes - otherwise known as primary urine
What is the basic renal process? FITB


What is the equation for amount excreted?
=Amount filtered + amount secreted - amount absorbed
What is the renal input in the basic renal process?
Renal artery
What is the renal output in the basic renal process?
Renal vein and ureter
What is the driving force of glomerular filtration pressures?
Hydrostatic pressure in glomerular capillaries = Pgc
What are the opposing pressures in the glomerular filtration?
Hydrostatic pressure of tubule (=Pt), osmotic pressure of plasma proteins in glomerular capillaries (= pi(3.14)gc)
How is ultrafiltration worked out?
Puf= Pgc - Pt - [pi]gc Around 10-20mmHg
What is the glomerular filtration rate?
GFR= Puf * Kf
What is Kf and what is it affected by?
Ultrafiltration coefficient - membrane permeability and SA available for filtration
What effect do kidney diseases have on functioning glomeruli?
Decreases, so reduces SA and thus reduces Kf
What occurs to Kf when drugs and hormones dilate glomerular arterioles?
Increase
What is the glomerular filtration rate?
The amount of fluid filtered from the glomeruli into Bowman’s capsule per unit of time (ml/min) Sum of filtration rate from all functioning nephrons
What occurs when nephrons are lost?
SA is lost, Kf decreases so overall GFR decreases
What does the renal blood flow do?
Delivers O2, nutrients and substances for excretion
What is the approx. value of RBF, RPF and FF?
FF= 0.2 RBF = 1/5 of cardiac output - 1L/min RPF= 0.6L/min
How is FF calculated?
Ratio between RPF and amount of filtrate filtered by glomerulus

