Question

1. What are the major contributions to glomerular filtration pressure, and what happens to GFR when these parameters change?

Answer 1

More precisely, GFR is the fluid flow rate between the glomerular capillaries and the Bowman's capsule:

{\displaystyle {\operatorname {d} Q \over \operatorname {d} t}=K_{f}\times (P_{G}-P_{B}-\Pi _{G}+\Pi _{B})}

Where:

• {\displaystyle {\operatorname {d} Q \over \operatorname {d} t}} is the GFR.
• {\displaystyle K_{f}} is called the filtration constant and is defined as the product of the hydraulic conductivity and the surface area of the glomerular capillaries.
• {\displaystyle P_{G}} is the hydrostatic pressure within the glomerular capillaries.
• {\displaystyle P_{B}} is the hydrostatic pressure within the Bowman's capsule.
• {\displaystyle \Pi _{G}} is the colloid osmotic pressure within the glomerular capillaries.
• and {\displaystyle \Pi _{B}} is the colloid osmotic pressure within the Bowman's capsule.

PGEdit

The hydrostatic pressure within the glomerular capillaries is determined by the pressure difference between the fluid entering immediately from the afferent arteriole and leaving through the efferent arteriole.

PBEdit

The pressure in the Bowman's capsule and proximal tubule can be determined by the difference between the pressure in the Bowman's capsule and the descending tubule

∏GEdit

Blood plasma has a good many proteins in it and they exert an inward directed force called the osmotic pressure on the water in hypotonic solutions across a membrane, i.e., in the Bowman's capsule. Because plasma proteins are virtually incapable of escaping the glomerular capillaries, this oncotic pressure is defined, simply, by the ideal gas law.

∏BEdit

This value is almost always taken to be equal to zero because in a healthy nephron, there should be no proteins in the Bowman's Capsule