GFR and renal blood flow

Question 1

How much is renal blood flow?

Answer 1

1.1L/min

Question 2

What is renal plasma flow?

Answer 2

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

Question 3

What does a lobe of the kidney consist of?

Answer 3

Renal pyramid and cortex directly above it. It is edged by blood vessels

Question 4

What is the difference between the interlobular and interlobar arteries?

Answer 4

Interlobular = in the lobes
Interlobar = between the lobes

Question 5

What is the difference between cortical and juxtamedullary nephrons?

Answer 5

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%

Question 6

What gets filtered by the glomerulus?

Answer 6

Blood cells and albumin

Question 7

What goes into the Bowmans Capsule?

Answer 7

Protein free plasma

Question 8

How much renal plasma is filtered?

Answer 8

About 20% of what arrives from the renal artery

Question 9

What is the normal GFR?

Answer 9

125ml/min

Question 10

How does efferent composition different to afferent composition?

Answer 10

efferent = more albumin, RBCs and WBCs as these are the things that are not filtered so remain in the blood.

Question 11

What is auto regulation?

Answer 11

Autoregulation is able to maintain GFR when blood pressure is within physiological limits (80-180mmHg).
These auto regulatory mechanisms keep GFR within normal limits

Question 12

What happens if blood pressure changes?

Answer 12

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.

Question 13

What is tubular glomerular feedback?

Answer 13

Links Na and Cl conc. at macula dense with control of renal arteriolar resistance by causing constriction or dilation of vessels.

Question 14

When is the sympathetic regulation of GFR used?

Answer 14

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.

Question 15

How does blood get from the heart and around the kidney (arteries)?

Answer 15

Aorta
Renal artery
Segmental artery
Lobular artery
Arcuate artery
Interlobular artery
Afferent arteriole
Glomerulus
Efferent arteriole 
Peritubular capillaries or Vasa recta

Question 16

How does blood get from the kidney back to the the heart (veins)?

Answer 16

Interlobular vein
Arcuate vein
Lobular vein
Segmental vein
Renal vein
IVC

Question 17

What are the three layers of the filtration barrier?

Answer 17

Capillary endothelial cells
Basement membrane (an acellular, negatively charged and gelatinous structure)
Podocytes with pedicels (feet)

Question 18

What effect does charge have on the selectivity of the filtration barrier?

Answer 18

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.

Question 19

What happens if there is an increase in NaCl?

Answer 19

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

Question 20

What happens if there is a decrease in NaCl?

Answer 20

Prostaglandins released and cause vasodilation of AA. This means GFR increases.

Only works in acute situations