###### Created: 2024-01-13 13:59 ###### Areas & Topics: #medicine #physics #physiology ###### Note Type: #permanent ###### Connected to: [[]] - The Starling Principle essentially states that the movement of extracellular fluid between blood and tissues is based on the balance between the hydrostatic pressure and the colloid osmotic pressure (also known as the oncotic pressure) inside and outside of capillaries - Hydrostatic pressure, in simple terms, is the amount of pressure a fluid exerts on the container it is in, which in this case are the capillaries. - [[Colloid]] osmotic pressure, also known as oncotic pressure, is the pressure which is made by solutes in blood moving along their concentration gradient (see [[Colloid]] for further explanation) - The Starling Equation is the mathematical formula used to calculate whether solutes are moving in or out of capillaries. - Outward force is defined as positive whilst inward force is defined as negative - When the number produced by the equation (Jv) is positive, then solvents are leaving the capillary (filtration). - When Jv is negative, then solvents are entering the capillary (absorption). - Classically, the Starling Equation shows the arteriolar end of capillaries undergo more filtration as hydrostatic pressure is greater than oncotic pressure at that end (i.e. forces are pushing solvent out of the capillaries more than the concentration gradient is pulling them back in), whilst the venous end undergoes more absorption as the hydrostatic pressure is lower than the oncotic pressure (i.e. the force of the concentration gradient pulling solvent back into the capillaries is greater than the hydrostatic pressure pushing them out). - However, in reality it appears to be that continuous [[Capillaries]] are generally in efflux across their entire length and the majority of absorption from tissues occurs via the lymph system. N.B. It's not necessary to know the entire equation by rote, but is important to know that the equation signifies the importance of hydrostatic pressure and oncotic pressure on the movement of solvents in and out of capillaries and tissues. ![[2108_Capillary_Exchange 1.jpg]] ![[Pasted image 20240113134428.png]] ### Resources https://en.wikipedia.org/wiki/Starling_equation https://en.wikipedia.org/wiki/Capillary#/media/File:2108_Capillary_Exchange.jpg