Glomerular filtration Flashcards
What is the fundamental functional unit of the kidney?
The nephron
Name the parts of the nephron in the order blood flows through them
Glomerulus Bowman's space Proximal tubule Loop of Henle Collecting duct
What is the combine blood flow to the kidneys?
1.1 litres per minute
What sort of membrane is there in the glomerulus?
Semi permeable
Where does the filtrate form?
Bowman’s space
What two forces drive the flow in glomerular ultrafiltration?
Hydrostatic
Osmotic/oncotic
How is glomerular pressure controlled?
Dilation of afferent arterioles
Contraction of efferent arterioles
What is the total osmotic glomerular pressure?
7.1 atm
What is the osmolality in the glomerulus?
0.0009 Osm.kg
Pressure of 17mmHg
What are the three layers that separate the blood from the lumen of Bowman’s capsule?
Endothelial cells of glomerular capillaries
Glomerular basement membrane
Epithelial cells of Bowman’s capsule
What is present in the endothelial cells of the glomerular capillaries?
Fenestrations
60nm
What charge do the endothelial cells have?
Negatively charged glycocalyx
Where else would you find negatively charged proteins?
Collagen fixed in the basement membrane
What is a podocyte?
Epithelial cell of Bowman’s capsule
What is a pedicel?
Projections from podocytes
Form extra barrier to movement of fluid
What is the filtration fraction?
Proportion of plasma flow that is filtered by the glomerulus
How do we calculate the filtration fraction?
Glomerular filtration rate/ Renal plasma flow
Describe molecules that are filtered
Less than 10kDa in size
Why would large molecules make it through the glomerulus?
Positive charge
Damage to glomerulus
What is the daily glomerular filtration rate?
180L a day
How much does each nephron filter?
30-50nL per min
What is the hydrostatic pressure in the Bowman’s capsule?
10mmHg
How do we measure glomerular filtration rate?
Substances that are filtered but not absorbed
Eg inulin.
How do we calculate glomerular filtration rate?
GFR = Concentration in urine x volume of urine over plasma concentration
How do we calculate estimated glomerular filtration rate?
eGFR=k/Concentration in plasma
k = (140-age)xmassxC
C=1.23 for men and 1.04 for women
Who can we use GFR for?
Only adults
As we age nephrons are lost and GFR falls
What is proteinuria?
Proteins in the urine, evidence of glomerular dysfunction
What is a cause of proteinuria?
Nephrotic syndrome
What is the name given to predominant dysfunction of the glomerulus?
Glomerulonephritis
What is congenital nephrotic syndrome?
Rare genetic disorder effecting either nephrin or podocin (found in podocytes)
Glomerulus is more permeable
