The table below compares the pressures of a systemic capillary with the surrounding tissue fluid in a healthy individual:
| Property | Capillary | Tissue fluid |
|---|---|---|
| Hydrostatic pressure | 5.40 kPa5.40\text{ kPa}5.40 kPa | 0.30 kPa0.30\text{ kPa}0.30 kPa |
| Oncotic pressure | 4.10 kPa4.10\text{ kPa}4.10 kPa | 0.10 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:
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.
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.
15 exam-style questions on OCR A A Level Biology Transport in animals. Each one has a worked solution and a mark scheme showing where the marks go.