Topic 3: Exchange: Formation and function of tissue fluids

Hydrostatic pressure

Pressure exerted by a fluid against a membrane

Blood hydrostatic pressure

Pressure exerted by blood against the wall of a capillary is called capillary hydrostatic pressure (CHP) and is the same as capillary blood preside

What is tissue fluid?

Tissue fluid (interstitial fluid) fills spaces between cells (interstitial space). It is the site of diffusion between blood and body cells, providing cells with nutrients and oxygen while removing waste products. It also helps fight infections as it forms part of the immune response.

Components of tissue fluid

Containing water, glucose, amino acids, fatty acids, ions and oxygen which bathes the tissue

How is tissue fluid different to blood plasma?

Doesn't have plasma proteins. Has no Red blood cells, fewer proteins and fewer white blood alls

Blood plasma contains proteins

e.g. Globular fibrinogens as well as albumin and other globular proteins called globulins

Tissue fluid formation

Formed by blood plasma (carrying dissolved substances) leaking from the capillaries.

The movement is by mass flow (the movement of fluids down a pressure gradient). There is a net outflow of plasma from the arterial end of capillaries due to higher blood pressure which creates high hydrostatic pressure.

Some tissue fluid is eventually reabsorbed. Waste products from cell metabolism (e.g. Carbon dioxide and urea) returned to the capillaries with the tissue fluid

Forced out: water molecules, dissolved minerals, glucose, small proteins and amino acids, fatty acids ,oxygen

Remains: red blood cells, platelets ,large proteins