Understanding the Starling forces

[Mantis Toboggin]

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So my mind has been warped in trying to learn this. To keep things simple, what I've learned is

Fluid goes out of capillaries due to: Hydrostatic pressure of blood, and oncotic pressures of interstitial fluid.

Fluid comes into capillaries due to: Hydrostatic pressure of interstitial fluids, and oncotic pressures of blood.

So apparently a commonly tested MCAT subject is an edema (excess fluid in interstitium).

What factors at the level of the capillary cause an edema? If I'm correct they are
(1) high hydrostatic bp (2) Low oncotic pressure in blood (lack of blood proteins) (3) Low hydrostatic pressure of interstitium (4) High oncotic pressure in interstitium

1.) Are these the correct factors that cause an edema?

2.) What is the relationship between interstitial oncotic and hydrostatic pressures with the lymph node reabsorption, and what questions might we expect o this subject?

Thanks

 

[sillyjoe]

So my mind has been warped in trying to learn this. To keep things simple, what I've learned is

Fluid goes out of capillaries due to: Hydrostatic pressure of blood, and oncotic pressures of interstitial fluid.

Fluid comes into capillaries due to: Hydrostatic pressure of interstitial fluids, and oncotic pressures of blood.

So apparently a commonly tested MCAT subject is an edema (excess fluid in interstitium).

What factors at the level of the capillary cause an edema? If I'm correct they are
(1) high hydrostatic bp (2) Low oncotic pressure in blood (lack of blood proteins) (3) Low hydrostatic pressure of interstitium (4) High oncotic pressure in interstitium

1.) Are these the correct factors that cause an edema?

2.) What is the relationship between interstitial oncotic and hydrostatic pressures with the lymph node reabsorption, and what questions might we expect o this subject?

Thanks

Let me just clarify a few points:

First, it is the osmotic pressure that pulls fluid out of the circulatory system. It is the ONCOTIC pressure that pulls fluid back into the circulatory system.

Edema can be caused by an increase in hydrostatic pressure, increase in osmotic pressure, and a decrease in oncotic pressure. In addition, edema can also be caused by an increase in vascular permeability of the capillaries which can be caused by things like mast cells releasing histamine. Some other examples include dysregulation of salts and poor lymphatic system. These are just a few examples.

In general, the way to think about it is: will the scenario described in the passage/question lead to an increase in extracellular fluid relative to normal. If the answer is yes, you will have edema.

Better to make a general rule than memorizing a plethora of causes.