Anatomy Question Capillary Exchange

Question

For my anatomy class homework we need to:

Explain capillary exchange as it refers to osmotic and hydrostatic pressure with an increase in blood pressure or a decrease in albumins. What would be the effect and why?

Can someone please explain this topic! Thanks so much!

Answer 1

So it is best in these types of questions to dissect out everything before talking about the answer.

Capillary: think of this as the thin netting between the arterial system and venous system where we can gain and loss based on "Starling Forces" ie oncotic and hydrostatic pressure both within the capillary and in the interstitium (tissue or extravascular).

Now lets look at each separately:

1. Hydrostatic pressure: outward force, increasing the pressure inside the tube pushes it out into the interstitium. The same is true if the pressure is higher in the interstitium as fluid will move from high pressure to low pressure to a point of balance.
2. Oncotic Pressure: This is a pulling pressure based on solute. With you increase the solute you create more pulling pressure towards.

Now that we have explained them lets simplify it. Hydrostatic is a pushing force, this is your blood pressure. Now your oncotic force is your pulling force, this is based largely on your albumin.

Now we can answer the question:

If you increase blood pressure, you have increased your hydrostatic force within the vessel therefore you will increase the flow of intravascular fluid to the interstitial space at this capillary level.

If you decrease Albumin you are decreasing that pulling pressure, therefore you will increase the uptake of fluid from the interstitium into the capillary and increase your intravascular volume.

The above is all based on Starling Forces equation:

(P_HS capillary - P_HS interstitum) - (P_O capillary - P_O interstitium) 

HS: hydrostatic pressure

O: Oncotic pressure

Goodluck and I hope this helps.