Scenario 1: You are a scientist involved in a top secrete autopsy and investigat

Question

Scenario 1: You are a scientist involved in a top secrete autopsy and investigation into the renal physiology of alien, crash landed in Yakima Valley!!! How secretly cool!!! You are working on your final report for General Goings. General Goings in not a scientist and needs everything to be explained. You are working on the portion of the report detailing Net Filtration Pressure of this alien and surprisingly it works just like humans!!!

I. Explain to General Goings what Net Filtration Pressure is and what a +NFP vs. a –NFP means.

II. You have determined that the colloid osmotic pressure of the capsular space is 25 mm of Hg, the hydrostatic pressure of the glomerular capillaries is 100 mm of Hg and the hydrostatic pressure of the capsular space is 25 mm of Hg. What is the overall Net Filtration Pressure of the alien?

Explanation / Answer

Net filtration pressure: It is the combination of three different pressures acting on glomerulus:

Glomerular capillary blood pressure (55 mm Hg) (or hydrostatic pressure of the capillaries): Pressure inside the capillaries of the glomerulus. It is similar to blood pressure

Bowman’s capsule hydrostatic pressure (15 mm Hg):It is hydrostatic pressure in the bowman’s capsule; the fluid in the capsule exerts pressure on its surroundings. This pressure works opposite to glomerular capillary blood pressure

Plasma colloid osmotic pressure (30 mm Hg): The colloid osmotic pressure is due to the difference in the dissolved contents in the plasma and the bowman’s capsule (plasma contains dissolved proteins, whereas fluid in the bowman’s capsule is a clear fluid devoid of proteins). Fluid in the bowman’s capsule tries to move in the direction of proteins (plasma) to dilute the high concentration of proteins

Net filtration pressure = glomerular capillary pressure – (Hydrostatic pressure of Bowman’s capsule + Plasma colloid osmotic pressure)

= 50 – (30 + 15)

= 55 – 45 = 10 mm Hg

A positive net filtration pressure means that glomerular hydrostatic pressure is more than the other two pressures together, and this makes the flow of filtrate into the Bowman’s capsule.

A negative net filtration pressure means that fluid enters the capillary, that is, fluid is absorbed back.

II. given that colloid osmotic pressure of capsular space = 25 m Hg

Glomerular hydrostatic pressure = 100 mm Hg

Hydrostatic pressure of capsular space = 25 mm Hg

Net positive pressure = 100 – (25 + 25) = 50 mm Hg

The net filtration pressure of the alien = 50 mm Hg

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