Peripheral Edema occurs due to some malfunctioning in the capillary dynamics in which there is an excess of fluid within the interstitial spaces.

1. Filtration of Lymph
2. Immune response
3. Returns good Lymph

Movement = Outward forces — Inward Forces

[HBP + TPOP] — [PPOP + THP]

Tissue Hydrostatic Pressure, a.k.a interstitial fluid hydrostatic pressure (IFHP), is the pressure exerted on the interstitial fluid by the the elastic recoil of the tissues in any region of the body.

Mechanical Forse

This force tends to push water from the interstitial fluid back into the capillaries

Plasma Protein Osmotic Pressure, a.k.a Blood Osmotic Pressure, is the osmotic force (water concentration gradient) which is the result of differences in water concentration between plasma and interstitial fluid.

Osmotic Force

This force tends to pull water from the interstitial fluid and back into the plasma in the capillaries

Tissue protein osmotic pressure(IFOP), a.k.a Interstitial Fluid Osmotic Pressure, is the result of differences in water concentration between plasma and interstitial fluid.

Osmotic Force (protein concentrations)

This force tends to pull water from the plasma in the capillaries into the interstitial fluid.

Hydrostatic blood pressure(BHP) is the mechanical pressure exerted on the fluid of plasma by the pumping of the heart during systole and by the elastic recoil and smooth muscle contraction in the walls of the arteries between heart beats during diastole.

Mechanical Force (heart = pump)

This force tends to push water from the capillaries into the interstitial fluid

Here, filtration refers to leaving the capillary and entering the interstitial fluid.

Absorption, on the other hand, is the uptake of fluid or nutrients from the interstitial fluid into the capillary

It’s also important to remember that different pressures exist at the arterial end vs. the venous end

Arterial End

• BHP > IFOP.
• Proteins (which can’t be diffused into interstitial fluid) in the plasm is what limits IFOP

Venous End

• IFOP > BHP
• Fluid of the tissues flows back into the venous end of the capillaries in order to carry waste away.

In arterioles that have been vasoconstricted (increasing resistance), endothelial cells experience an increased shearing force from turbulent flow.

This shear force causes the release of nitric oxide (EDRF : endothelium-derived relaxing factor) which, in turn, causes a relaxation of the arteriole smooth muscle, or vasodilation.

Active tissues tend to automatically receive increased blood flow.

One mechanism for this is the presence of metabolic agents in a tissue, which triggers a reflex for vasodilation of arterioles. Otherwise, these metabolites build up in the tissue.