You are rushing to get to class on time, and in your haste you catch your foot o

Question

You are rushing to get to class on time, and in your haste you catch your foot on a stair and turn your ankle hard. Ouch! You sit down on the stairs to examine your injured ankle and notice that it has already begun to swell. You cannot put your weight on the injured ankle and suspect that you have torn a ligament that holds the ankle b one together. Many of the cells in the damaged area of tissue have broken open and released the contents of their cytoplasm into the interstitial fluid. Assume in this simplified example that cells in the damaged tissue have broken open but most of the capillary beds are intact.

A.) which of the four pressures ( HPc, OPc, HPif, OPif) that relate to capillary dynamics would be most affected in this situation? Would this pressure be increased ? Explain how the change in this pressure would cause the swelling in your ankle.

B) As you realize the situation you are in and all of the work you have to do this week (you SO don't have time for this!) your heart begins to race and your blood pressure increases. Is this likely to help the swelling in your ankle or make it worse? Explain, referencing the important change(s) in pressures across the capillary.

C.) Luckily an x-ray at the emergency room reveals that you do not have any broken bones, and that your ligament tear is minor. You don't need a cast, but are instructed to wear a compression bandage on your ankle to reduce the swelling. Which of the four pressures that related to capillary dynamics would be most affected by the bandaging of the swollen ankle? would this pressure be increased or decreased? Explain how the change in this pressure would reduce the swelling in your ankle?

Explanation / Answer

Net pressure = HPc + OPif - HPif - OPc

A. Proteins and other solutes will leak out of the cell, into the interstitial fluid. This would increase the OPif. According to the equation above, OPif contributes positively to the net outward pressure. So, it will increase the oedema and cause swelling.

B. The increased blood pressure will increase the capillary hydrostatic pressure ( HPc ). According to the above equation, HPc contributes positively to the net outward pressure. So, it will increase the oedema and swelling.

C. Compression bandage would cause the tissues to compress and thus increase the hydrostatic pressure of the interstitial fluid, i.e, HPif. According to the above equation, HPif contributes negatively to the net outward pressure. So, it will decrease the oedema and reduce swelling.

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