Renal BF, GFR

Question 1

What type of blood flow occurs throughout the kidneys?

Answer 1

Renal blood flow has 2 systems: the renal artery splits into several other arteries to eventually form efferent arterioles.
This splits into peritubular capillaries and the vasa recta, which join to form interlobular veins, which eventually lead to the renal vein

Question 2

What drives movement of solutes and solvents in renal blood flow?

Answer 2

Hay a Pa difference between the end of the efferent and end of the afferent arteriole. (from high to low pa).
In the glomerulus capillary hydrostatic pa drives the fluid out to make the filtrate
In the descending vasarecta (maintains conc gradients in the medulla) the osmotic pa drives solutes in

Question 3

Describe the nerve supply of renal vessels, and the reno-renal reflex

Answer 3

• Sympathetic preganglionic is from T10-L2
• Postganglionic neurons lie in SMA and renal artery ganglion
• Nociceptive afferents are responsible for the reno-renal-reflex (see image)

Question 4

What maintains GFR?

Answer 4

This eqn shows that higher hydrostatic pa and lower oncotic pa will drive more fluid out into the bowmans capsule.
To maintain filtration pa, hydrostatic pa is greater in the afferent end. In order for filtration to stop, osmotic pa is higher in the efferent end
Also, the higher the permeability, the greater the GFR

Question 5

How does the renal system respond to hypotension? What happens if this response system is hindered?

Answer 5

This is to pressurise the glomerulus

Question 6

How do we measure renal blood flow?

Answer 6

Fick principle -substance amount in the blood that flows in an organ= amount that must flow out that organ.

So, applying the Fick principle, the amount of PAH entering the kidneys through the renal arteries= amount of PAH in the urine + the amount of PAH which leaves the kidneys via the renal veins.

This in the form of an eqn:

Question 7

How do you measure GFR and clearance?

Answer 7