GFR and renal blood flow Flashcards
How much is renal blood flow?
1.1L/min
What is renal plasma flow?
This is the amount of blood flow that is just plasma.
Haematocrit is the volume percentage of red blood cells. This is normally 45% so
Renal Plasma Flow: 0.55x1.1L/min = 605 ml/min of plasma
What does a lobe of the kidney consist of?
Renal pyramid and cortex directly above it. It is edged by blood vessels
What is the difference between the interlobular and interlobar arteries?
Interlobular = in the lobes Interlobar = between the lobes
What is the difference between cortical and juxtamedullary nephrons?
Juxtamedullary:
-More into the medulla than the cortical nephrons
-Bigger glomerulus
-Loop of Henle is longer and into inner part of medulla
-Diameter of afferent arterioles (AA) to efferent arterioles (EA) are same (in cortical, AA:EA =2:1)
-EA from vasa recta (cortical from peritubular capillary)
Poor sympathetic innervation
Low concentration of renin (cortical = high)
Juxtamedullary=10% Cortical=90%
What gets filtered by the glomerulus?
Blood cells and albumin
What goes into the Bowmans Capsule?
Protein free plasma
How much renal plasma is filtered?
About 20% of what arrives from the renal artery
What is the normal GFR?
125ml/min
How does efferent composition different to afferent composition?
efferent = more albumin, RBCs and WBCs as these are the things that are not filtered so remain in the blood.
What is auto regulation?
Autoregulation is able to maintain GFR when blood pressure is within physiological limits (80-180mmHg).
These auto regulatory mechanisms keep GFR within normal limits
What happens if blood pressure changes?
Afferent arterioles constrict if pressure increases which means the GFR remains unchanged.
This is a myogenic response
The efferent arteries could dilate and this would have the same effect.
The opposite happens if blood pressure decreases.
What is tubular glomerular feedback?
Links Na and Cl conc. at macula dense with control of renal arteriolar resistance by causing constriction or dilation of vessels.
When is the sympathetic regulation of GFR used?
Low, very little effect
Effect in fight / flight, ischaemia or severe haemorrhage.
Vasoconstriction occurs as a result which conserves blood volume (haemorrhage) and can cause a fall in GFR.
How does blood get from the heart and around the kidney (arteries)?
Aorta Renal artery Segmental artery Lobular artery Arcuate artery Interlobular artery Afferent arteriole Glomerulus Efferent arteriole Peritubular capillaries or Vasa recta
How does blood get from the kidney back to the the heart (veins)?
Interlobular vein Arcuate vein Lobular vein Segmental vein Renal vein IVC
What are the three layers of the filtration barrier?
Capillary endothelial cells Basement membrane (an acellular, negatively charged and gelatinous structure) Podocytes with pedicels (feet)
What effect does charge have on the selectivity of the filtration barrier?
Postively charged things can get through the membrane more easily as basement membrane is negatively charged.
Not more difficult to get through if negative as repelled.
What happens if there is an increase in NaCl?
Adenosine is released which causes vasoconstriction of AA via A1 receptors by vasodilation of EA by A2 receptors.
This reduces the pressure gradient across glomerulus and thus slows GFR.
Only works in acute situations
What happens if there is a decrease in NaCl?
Prostaglandins released and cause vasodilation of AA. This means GFR increases.
Only works in acute situations
