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Exchange and transport

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Question 41

The table below compares the pressures of a systemic capillary with the surrounding tissue fluid in a healthy individual:

PropertyCapillaryTissue fluid
Hydrostatic pressure5.40 kPa5.40\text{ kPa}5.40 kPa0.30 kPa0.30\text{ kPa}0.30 kPa
Oncotic pressure4.10 kPa4.10\text{ kPa}4.10 kPa0.10 kPa0.10\text{ kPa}0.10 kPa

The net movement of fluid between the capillary and tissue fluid depends on the net driving force (JvJ_vJv​), calculated using Starling's equation:

Jv=(Pc−Pi)−σ(πc−πi) J_v = (P_c - P_i) - \sigma(\pi_c - \pi_i) Jv​=(Pc​−Pi​)−σ(πc​−πi​)

Where:

  • PcP_cPc​ = capillary hydrostatic pressure
  • PiP_iPi​ = tissue fluid hydrostatic pressure
  • πc\pi_cπc​ = capillary oncotic pressure
  • πi\pi_iπi​ = tissue fluid oncotic pressure
  • σ\sigmaσ = reflectance factor (representing capillary permeability, ranging from 0 for totally permeable to 1 for totally impermeable)
a.

In this specific capillary bed, the reflectance factor (σ\sigmaσ) is 0.750.750.75. Use this information and the data in the table to calculate the net driving force, JvJ_vJv​, and predict the direction of net fluid movement.

[4]
b.

Nephrotic syndrome is a kidney disorder that results in the excretion of large quantities of proteins (such as albumin) into the urine, significantly lowering plasma protein concentration. Suggest the effect of nephrotic syndrome on the net driving force (JvJ_vJv​) and explain how this affects the volume of tissue fluid formed.

[4]

Exchange and transport Questions

  1. A Level
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  3. /Exchange and transport