Describe and explain how substances dissolved in blood plasma, such as oxygen and glucose enter the tissue fluid from the capillaries.

Simple molecules are able to move through the capillaries down the concentration gradient. An example of this would be oxygen moving from oxygen rich blood into the surrounding muscle. Other molecules are able to move across permeable membranes with the plasma where the hydrostatic pressure in the capillary is higher than that of the tissue fluid. This moves down the pressure gradient.