is the subglycocalyx oncotic pressure is the hydraulic conductivity of the membrane is the surface area for filtration is Staverman's reflection coefficient Pressures are often measured in millimetres of mercury (mmHg), and the filtration coefficient in millilitres per minute per millimetre of mercury (ml·min−1·mmHg−1). Filtration coefficient In some texts the product of hydraulic conductivity and surface area is called the filtration co-efficient Kfc. Reflection coefficient Staverman's reflection coefficient, σ, is a unitless constant that is specific to the permeability of a membrane to a given solute. The Starling equation, written without σ, describes the flow of a solvent across a membrane that is impermeable to the solutes contained within the solution. σn corrects for the partial permeability of a semipermeable membrane to a solute n. Where σ is close to 1, the plasma membrane is less permeable to the denotated species (for example, larger molecules such as albumin and other plasma proteins), which may flow across the endothelial lining, from higher to lower concentrations, more slowly, while allowing water and smaller solutes through the glycocalyx filter to the extravascular space. Glomerular capillaries have a reflection coefficient close to 1 as normally no protein crosses into the glomerular filtrate. In contrast, hepatic sinusoids have no reflection coefficient as they are fully permeable to protein. Hepatic interstitial fluid within the Space of Diss has the same colloid osmotic pressure as plasma and so hepatocyte synthesis of albumin can be regulated. Albumin and other proteins in the interstitial spaces return to the circulation via lymph. Approximated values Following are typically quoted values for the variables in the classic Starling equation: It is reasoned that some albumin escapes from the capillaries and enters the interstitial fluid where it would produce a flow of water equivalent to that produced by a hydrostatic pressure of +3 mmHg. Thus, the difference in protein concentration would produce a flow of fluid into the vessel at the venous end equivalent to 28 − 3 = 25 mmHg of hydrostatic pressure. The total oncotic pressure present at the venous end could be considered as +25 mmHg. In the beginning (arteriolar end) of a capillary, there is a net driving force () outwards from the capillary of +9 mmHg. In the end (venular end), on the other hand, there is a net driving force of −8 mmHg. Assuming that the net driving force declines linearly, then there is a mean net